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GARNet Research Roundup: May 29th 2020

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Published on: May 29, 2020

This bumper GARNet Research Roundup begins with two sets of papers in related areas. First are three papers that investigate the biology of plasmodesmatata. These include work from the Faulkner lab at the JIC, the Band lab at Nottingham and a broad European collaboration that includes co-authors from Durham, Cambridge and St Andrews.

The second set of two papers features work on different species of Kalanchoë, which is a key model for the study of CAM. This research is from the Hartwell lab in Liverpool and the Borland lab in Newcastle.

The fifth paper is from RHUL and looks at the relationship between nucleus and chloroplast signaling. The sixth paper is from QMUL and introduces research suggesting that a rethink is needed in our understanding of the relationship between chloroplast movement and photoprotection.

The next paper is from the University of the West of England and looks at the effect of ionising radiation on multiple generation of Arabidopsis growth whilst the eighth paper investigates the relationship between starch degradation and stomatal movements in guard cells and includes co-authors from Essex and Glasgow.

The next two papers include research undertaken in Cambridge; firstly looking at the integration of signalling between karrikin and strigolactone signaling in rice and secondly identifying a novel mRNA thermoswitch that controls thermomorphogenesis.

The next paper is a pan-European project led from Nottingham that has characterised the role of the CEP5 peptide during regulation of osmostic stress, drought and auxin signaling.

The twelveth paper is from the University of Warwick and also looks at the auxin response, this time during senescence. The next paper as well includes co-authors from Warwick in a study that investigates the global regulatory role for the histone acetyltransferase GCN5.

The penultimate paper includes co-authors from Norwich Research Park looks at the evolution of immune NLR signaling between closely related species. The final paper includes Patrick Hussey from Durham as a co-author in a Spanish study that identifies an uncharacterized compartment of the plant vacuolar trafficking pathway.

Cheval C, Samwald S, Johnston MG, de Keijzer J, Breakspear A, Liu X, Bellandi A, Kadota Y, Zipfel C, Faulkner C (2020) Chitin perception in plasmodesmata characterizes submembrane immune-signaling specificity in plants. Proc Natl Acad Sci U S A. 2020 Apr 28;117(17):9621-9629. doi: 10.1073/pnas.1907799117 Open Access

Cecilia Cheval, Sebastian Samwald and Matthew Johnston are co-first authors on this work from the Faulkner lab at the John Innes Centre. They looked at a plasmodesmata-localised plasma membrane microdomain, which hosts specific receptors and responses. They showed that immune chitin signalling requires the plasmodesmal PM localised LYM2 and LYK4 proteins. Overall this demonstrates that distinct membrane domains can integrate common signals to produce a localized response.

https://www.pnas.org/content/117/17/9621.long

Brault ML, Petit JD, Immel F, Nicolas WJ, Glavier M, Brocard L, Gaston A, Fouché M, Hawkins TJ, Crowet JM, Grison MS, Germain V, Rocher M, Kraner M, Alva V, Claverol S, Paterlini A, Helariutta Y, Deleu M, Lins L, Tilsner J, Bayer EM (2020) Multiple C2 domains and transmembrane region proteins (MCTPs) tether membranes at plasmodesmata. EMBO Rep. 2019 Aug;20(8):e47182. doi: 10.15252/embr.201847182 Open Access

Marie Brault works with Emmualle Bayer is first author on this French-led pan-European study that includes co-authors from Durham, Cambridge and St Andrews. They investigate the plasmodesmal plasma membrane and show that Multiple C2 domains and transmembrane region proteins (MCTP) are needed to tether ER-PM linkages at this location. They show Atmctp3/Atmctp4 loss of function double mutants have plant developmental defects demonstrating that MCTPs also play a significant role in cell-to-cell signalling.

https://www.embopress.org/doi/full/10.15252/embr.201847182#.XSRrrlB2xG0.twitter

Mellor NL, Voß U, Janes G, Bennett MJ, Wells DM, Band LR (2020) Auxin fluxes through plasmodesmata modify root-tip auxin distribution. Development. doi: 10.1242/dev.181669 Open Access

Nathan Mellor leads this research from the University of Nottingham that has developed a model to explain auxin movement around the Arabidopsis root tip. They propose that carrier mediated movement is not sufficient foir this and that there must be a symplastic route via plasmodesmata. This introduces plasmodesmata as playing a key role in hormone signaling.

https://dev.biologists.org/content/147/6/dev181669

GARNet committee member Yoselin Benitez-Alfonso discusses her labs work on plasmodesmata in the first #GARNetPresents webinar

Boxall SF, Kadu N, Dever LV, Kneřová J, Waller JL, Gould PJD, Hartwell J (2020) Kalanchoë PPC1 Is Essential for Crassulacean Acid Metabolism and the Regulation of Core Circadian Clock and Guard Cell Signaling Genes. Plant Cell. doi: 10.1105/tpc.19.00481

Susie Boxall leads this study from the Hartwell lab at the University of Liverpool in which they investigate the role of the phosphoenolpyruvate carboxylase gene in the CAM-plant Kalanchoë laxiflora. They use RNA interference to silence the PPC1 gene and show that these transgenic plants have defects in guard cell signaling and regulation of the circadian clock. These findings provide direct evidence that the regulatory patterns of key guard cell signaling genes are linked with the characteristic inverse pattern of stomatal opening and closing during CAM.

http://www.plantcell.org/content/32/4/1136.long

Abraham PE, Hurtado Castano N, Cowan-Turner D, Barnes J, Poudel S, Hettich R, Flütsch S, Santelia D, Borland AM (2020) Peeling back the layers of Crassulacean acid metabolism: functional differentiation between Kalanchoë fedtschenkoi epidermis and mesophyll proteomes. Plant J. doi: 10.1111/tpj.14757 Open Access

Paul Abraham is first author on this work from the Borland lab at the University of Newcastle. They are working with the CAM species Kalanchoë fedtschenkoi and here perform a large-scale proteomics analysis of the epidermis and mesophyll cell layers. This reveals that different proteins and biological processes are enriched in each layer, showing how plants adapt to hot and dry environments by modifying leaf physiology for improved plant sustainability.

Loudya N, Okunola T, He J, Jarvis P, López-Juez E (2020) Retrograde signalling in a virescent mutant triggers an anterograde delay of chloroplast biogenesis that requires GUN1 and is essential for survival Philos Trans R Soc Lond B Biol Sci. 2020;375(1801):20190400. doi:10.1098/rstb.2019.0400 Open Access

Naresh Loudya from Royal Hollaway University of London is first author on this work that investigates the relationship between nucleus and chloroplast gene expression in the control of chloroplast biogenesis. They analyse the cue8 mutant that shows differential changes in the activity of plastid-encoded and nucleus-encoded polymerases.

Naresh discussed this paper on the GARNet Community podcast.

Wilson S, Ruban AV (2020) Rethinking the influence of chloroplast movements on non-photochemical quenching and photoprotection. Plant Physiol. 2020 May 13. pii: pp.00549.2020. doi: 10.1104/pp.20.00549 Open Access

Sam Wilson is first author on this work from the Ruban lab at the Queen Mary University of London. In this study they have assessed the relationship between blue light induced chloroplast relocation and high-light tolerance. Their data argues against the existence of a chloroplast movement-dependent component of the non-photochemical quenching (NPQ) respose. Therefore the authors suggest that thinking on the influence of chloroplast movements on photoprotection should be reevaluated.

Caplin NM, Halliday A, Willey NJ (2020) Developmental, Morphological and Physiological Traits in Plants Exposed for Five Generations to Chronic Low-Level Ionising Radiation. Front Plant Sci. doi: 10.3389/fpls.2020.00389 Open Access

Nicol Caplin is first author on this research from the University of the West of England that looked at the effects of ionising radiation (IR) on seven generations of Arabidopsis growth. They found that although chronic exposure to IR caused some individual trait changes, these are not carried across generations at the population level but still call for more research in this area to be sure of the current regulations provided by the International Commission for Radiological Protection (ICRP).

https://www.frontiersin.org/articles/10.3389/fpls.2020.00389/full

Flütsch S, Wang Y, Takemiya A, Vialet-Chabrand SR, Klejchova M, Nigro A, Hills A, Lawson T, Blatt MR, Santelia D (2020) Guard Cell Starch Degradation Yields Glucose for Rapid Stomatal Opening in Arabidopsis. Plant Cell. doi: 10.1105/tpc.18.00802

This Swiss-led study has Sabrina Flütsch as first author and co-authors from Essex and Glasgow. They looked at the integration of starch degradation in guard cells with the kinetics of stomatal reopening. The timing of rapid stomatal unopening was unchanged in starch degrading mutants but there were alterations in slower responses, most likely due to alterations in the composition of guard cell starch metabolites.

Choi J, Lee T, Cho J, Servante EK, Pucker B, Summers W, Bowden S, Rahimi M, An K, An G, Bouwmeester HJ, Wallington EJ, Oldroyd G, Paszkowski U (2020) The negative regulator SMAX1 controls mycorrhizal symbiosis and strigolactone biosynthesis in rice. Nat Commun. doi: 10.1038/s41467-020-16021-1 Open Access

This research is led from the Paszkowski lab at the University of Cambridge by Jeongmin Choi. They have found that the rice ortholog of Arabidopsis Suppressor of MAX2-1 plays a novel role to link the pre-symbiotic perception of arbuscular mycorrhizal fungi with karrikin and strigolactone signaling. This response functions through a modification of the D14L signalling pathway.

Chung BYW, Balcerowicz M, Di Antonio M, Jaeger KE, Geng F, Franaszek K, Marriott P, Brierley I, Firth AE, Wigge PA (2020) An RNA thermoswitch regulates daytime growth in Arabidopsis. Nat Plants. doi: 10.1038/s41477-020-0633-3

This Wigge lab-led collaboration includes Betty Chung as first author and investigate the role of the PIF7 messenger RNA as a thermoswitch that activates the thermomorphogenesis pathway. This is controlled by the formation of an RNA hairpin within the mRNA and they show that this mechanism is conserved so controls translation of other mRNAs, enabling the plant to respond and adapt rapidly to high temperatures.

Smith S, Zhu S, Joos L, Roberts I, Nikonorova N, Vu LD, Stes E, Cho H, Larrieu A, Xuan W, Goodall B, van de Cotte B, Waite JM, Rigal A, R Harborough SR, Persiau G, Vanneste S, Kirschner GK, Vandermarliere E, Martens L, Stahl Y, Audenaert D, Friml J, Felix G, Simon R, Bennett M, Bishopp A, De Jaeger G, Ljung K, Kepinski S, Robert S, Nemhauser J, Hwang I, Gevaert K, Beeckman T, De Smet I (2020) The CEP5 peptide promotes abiotic stress tolerance, as revealed by quantitative proteomics, and attenuates the AUX/IAA equilibrium in Arabidopsis. Mol Cell Proteomics. 2020 May 13. pii: mcp.RA119.001826. doi: 10.1074/mcp.RA119.001826 Open Access

Stephanie Smith at the University of Nottingham is first author on this collaboration between researchers in 8 different countries. They use quantitative proteomics to assess the role of the CEP8 peptide in the response to osmotic and drought stress and in the control of auxin signaling.

Gören-Sağlam N, Harrison E, Breeze E, Öz G, Buchanan-Wollaston V (2020) Analysis of the impact of indole-3-acetic acid (IAA) on gene expression during leaf senescence in Arabidopsis thaliana. Physiol Mol Biol Plants. doi: 10.1007/s12298-019-00752-7

Nihal Gören-Sağlam is first author on this study from the University of Warwick in which they investigate the role of externally applied auxin on senescence in Arabidopsis thaliana. They show that PSII activity, as a determinant of chlorophyll fluorescence, declined after auxin treatment and that this response changed across different leaves.

Kim S, Piquerez SJM, Ramirez-Prado JS, Mastorakis E, Veluchamy A, Latrasse D, Manza-Mianza D, Brik-Chaouche R, Huang Y, Rodriguez-Granados NY, Concia L, Blein T, Citerne S, Bendahmane A, Bergounioux C, Crespi M, Mahfouz MM, Raynaud C, Hirt H, Ntoukakis V, Benhamed M (2020) GCN5 modulates salicylic acid homeostasis by regulating H3K14ac levels at the 5′ and 3′ ends of its target genes. Nucleic Acids Res. doi: 10.1093/nar/gkaa369 Open Access

This French-led study includes Soonkap Kim as first author and co-authors from the University of Warwick. They analysed the role of the histone acetyltransferase GCN5 in global control of gene expression. They used several methodologies (ATAC-seq, ChIP-seq and RNA-seq) to assess the effect of GCN5 loss-of-function on the expression and epigenetic regulation of its target genes.

Baggs E, Monroe JG, Thanki AS, O’Grady R, Schudoma C, Haerty W, Krasileva KV (2020) Convergent Loss of an EDS1/PAD4 Signaling Pathway in Several Plant Lineages Reveals Co-evolved Components of Plant Immunity and Drought Response. Plant Cell. doi: 10.1105/tpc.19.00903 Open Access

This research is led by Erin Baggs in the Krasileva lab at the University of California Berkeley and includes co-authors from Norwich Research Park. They assessed the variation in nucleotide-binding leucine-rich repeat receptors (NLRs) involved in plant immunity, focusing on closely related species that have different NLR compositions. Loss of NLRs corresponds to other changes in downstream immune signaling complexes. This excellent extensive multi-omic analysis provides evolutionary evidence for the rewiring of immunity in some plant lineages.

http://www.plantcell.org/content/early/2020/05/14/tpc.19.00903.long

Delgadillo MO, Ruano G, Zouhar J, Sauer M, Shen J, Lazarova A, Sanmartín M, Lai LTF, Deng C, Wang P, Hussey PJ, Sánchez-Serrano JJ, Jiang L, Rojo E (2020) MTV proteins unveil ER- and microtubule-associated compartments in the plant vacuolar trafficking pathway. Proc Natl Acad Sci U S A. doi: 10.1073/pnas.1919820117

María Otilia Delgadillo is first author on this Spanish-led study that includes Patrick Hussey from Durham as a co-author. The study identifies 13 components of the vacuolar trafficking machinery through a genetic screen for mutants that abnormally secrete the synthetic vacuolar cargo VAC2. Eight of these components localize at the interface between the trans-Golgi network (TGN) and the multivesicular bodies (MVBs), which excitingly reveals a previously uncharacterized compartment of the plant vacuolar trafficking pathway.

https://www.pnas.org/content/117/20/10623

GARNet Research Roundup: May 17th

by Geraint

Categories: Cambridge University, Durham University, Essex University, Glasgow University, Global, James Hutton Institute, SLCU, Uncategorized, University of Essex

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Published on: May 17, 2018

This weeks GARNet research roundup includes six excellent papers investigating many aspects of Arabidopsis cell biology. Firstly Eirini Kaiserli from Glasgow introduces a novel regulator of blue-light signaling. Second is a paper that analyses the circadian clock with single cell resolution and is led by James Locke (SLCU) and Anthony Hall (Earlham Institute). The next two papers investigate different aspects of hormone signaling, with Keith Lindsey’s group at Durham looking at the relationshop between the HYDRA protein and the auxin response whilst Ottoline Leysers group in Cambridge looks at the link between auxin and cytokinin during shoot growth. The fifth paper from Phillip Mullineaux (University of Essex) provides a genome-wide analysis into the role of HEAT SHOCK TRANSCRIPTION FACTORA1b protein. The final paper from the lab of Piers Hemsley (James Hutton Institute, University of Dundee) should be of interest to many plant molecular biologists as they assess the functional significance of different epitope tags.

Perrella G, Davidson MLH, O’Donnell L, Nastase AM, Herzyk P, Breton G, Pruneda-Paz JL, Kay SA, Chory J, Kaiserli E (2018) ZINC-FINGER interactions mediate transcriptional regulation of hypocotyl growth in Arabidopsis. Proc Natl Acad Sci U S A.. pii: 201718099. doi: 10.1073/pnas.1718099115

Open Access

Eirini Kaiserli (University of Glasgow) leads this study that identifies the ZINC-FINGER HOMEODOMAIN 10 (ZFHD10) as a novel regulator of light signaling. ZFHD10 physically interacts with TANDEM ZINC-FINGER PLUS3 (TZP) and these proteins coassociate at promotors that are blue-light regulated. These results reveal of novel mechanism of action for the key multiple signal integrator TZP in the light regulated growth of Arabidopsis hypocotyls.

Eirini discusses this paper on the GARNet YouTube channel.

Gould PD, Domijan M, Greenwood M, Tokuda IT, Rees H, Kozma-Bognar L, Hall AJ, Locke JC (2018). Coordination of robust single cell rhythms in the Arabidopsis circadian clock via spatial waves of gene expression. Elife. 26;7. pii: e31700. doi: 10.7554/eLife.31700 Open Access

https://elifesciences.org/articles/31700

This paper is led by James Locke (SLCU) and Anthony Hall (Earlham) and investigates the circadian clock at single cell resolution. They use Arabidopsis plants grown in constant environmental conditions to show two desynchronised yet robust single cell oscillations that move both up and down the root. Their results indicate that the clock shows cell-to-cell coupling and they they modeled this relationship to recapitulate the observed waves of activity. Overall their results are suggestive of multiple coordination points for the Arabidopsis clock, which is different from the mammalian system of regulation.

http://dev.biologists.org/content/145/10/dev160572

Short E, Leighton M, Imriz G, Liu D, Cope-Selby N, Hetherington F, Smertenko A, Hussey PJ, Topping JF, Lindsey K (2018) Epidermal expression of a sterol biosynthesis gene regulates root growth by a non-cell autonomous mechanism in Arabidopsis. Development . pii: dev.160572. doi: 10.1242/dev.160572 Open Access

This collaboration between the research groups of Keith Lindsey and Patrick Hussey at the University of Durham investigates the role of the HYDRA1 (HYD1) sterol Δ8-Δ7 isomerase in epidermal patterning. This tissue shows highest HYD1 expression and hyd mutants have major root patterning defects. Tissue-specific expression of HYD1 indicates that it is involved with some type of non-cell autonomous signaling. Analysis of PIN1 and PIN2 protein expression suggests that auxin might be this functional signal

http://www.plantphysiol.org/content/early/2018/05/01/pp.17.01691.long

Waldie T, Leyser O (2018) Cytokinin targets auxin transport to promote shoot branching. Plant Physiol. 2018 May 1. pii: pp.01691.2017. doi: 10.1104/pp.17.01691.Open Access

This study from the lab of Ottoline Leyser (SLCU) investigates the integration between the plant hormones cytokinin and auxin. They investigate the role of cytokinin in shoot branching through analysis of Arabidopsis Response Regulators (ARRs) mutants. They show arr mutant phenotypes correlate with changes in stem auxin transport mediated by the PIN3, PIN4 and PIN7 efflux carriers, the expression of each respond to cytokinin signaling. Overall this study identifies a novel alternative pathway by which cytokinin impacts bud outgrowth through alterations in auxin transport.

Albihlal WS, Irabonosi O, Blein T, Persad R, Chernukhin I, Crespi M, Bechtold U, Mullineaux PM (2018) Arabidopsis Heat Shock Transcription FactorA1b regulates multiple developmental genes under benign and stress conditions. J Exp Bot. doi: 10.1093/jxb/ery142 Open Access

Phillip Mullineaux (University of Essex) leads this collaboration with French colleagues in a study that investigates the genome-wide targets of the HEAT SHOCK TRANSCRIPTION FACTORA1b (HSFA1b) protein. Under non-stress ad heat-stress conditions they showed that 1000s of genes are differentially expressed with a smaller proportion of genes showing different levels of direct interaction. The indirect targets of HSFA1b are regulated through a network of 27 transcription factors and they also provide evidence for the role of hundreds of natural antisense non-coding RNA in the regulation of HSFA1b targets. Overall they show that HSFA1b is a key regulator of environmental cues to regulate both developmental genes and those involved in stress tolerance.

Hurst CH, Turnbull D, Myles SM, Leslie K, Keinath NF, Hemsley PA (2018) Variable effects of C-terminal tags on FLS2 function – not all epitope tags are created equal. Plant Physiol. doi: 10.1104/pp.17.01700 Open Access

This study from the Hemsley lab (James Hutton Institute, University of Dundee) is a cautionary tale on the use and interpretation of results obtained from experiments with commonly-used epitope tags. They assessed the activity of plants containing transgenic FLS2 proteins, which is a receptor-like kinase (RLKs) involved in the defence response. They show that various FLS2 C-terminal epitope fusions reveal highly variable and unpredictable outputs, indicating that the presence of different tags significantly alters protein function. This finding might require a reassessment of many experiments that rely on interpreting the function of epitope-tagged proteins and has significant for many if not all plant molecular biologists.

Arabidopsis Research Roundup: Nov 24th

by Geraint

Categories: Essex University, Glasgow University, Global, John Innes Centre, Nottingham University, SLCU, University of Bristol, University of Essex, University of Sheffield, University of Southampton

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Published on: November 24, 2017

The week’s UK Arabidopsis research roundup includes seven papers from groups who work on a range of topics.

Firstly Antony Dodd (Bristol) investigates the role of sugar signaling during hypocotyl elongation and provides an audio description of this groups work. Secondly Mike Holdsworth (Nottingham) leads a paper that demonstrates the importance of the N-rule pathway in the response to abiotic stresses. Thirdly are a set of papers that have developed models on three different topics. Mike Blatt’s group at Glasgow University has a cross-scale model that is applied to stomatal opening whilst Stan Maree and Veronica Griensien (JIC) use modeling to predict how the topology of pavement cells is determined. Finally Arabidopsis is used as an example that fits a model that investigates how critical mutation rate (CMR) changes with population size. In the sixth paper Lorraine Williams and colleagues (University of Southampton) investigate the function of a rice transport protein involved in manganese tolerance by expressing it in Arabidopsis. The final paper from Jerzy Paszkowski (SLCU) outlines a novel screening strategy for retrotransposons and the identification of an ecotype specific element.

Simon NM, Kusakina J, Fernández-López Á, Chembath A, Belbin FE, Dodd AN (2017) The energy-signalling hub SnRK1 is important for sucrose-induced hypocotyl elongation. Plant Physiol. doi: 10.1104/pp.17.01395

Open Access

This UK-wide collaboration is led by Anthony Dodd at the University of Bristol and has looked at the factors that control hypocotyl elongation in response to sugar signalling. This response is integrated through the sugar-signalling hub, SnRK1 and is regulated by trehalose-6-phosphate (Tre6P). They also integrate hormone signalling and the influence of diurnal rhythms into the control of this process, importantly showing that the ubiquitous sugar regulator hexokinase is not involved in this process.

Antony kindly provides an audio description of this research that can be found on YouTube or on the GARNet iTunes channel. Please subscribe!

Vicente J, Mendiondo GM, Movahedi M, Peirats-Llobet M, Juan YT, Shen YY, Dambire C, Smart K, Rodriguez PL, Charng YY, Gray JE, Holdsworth MJ (2017) The Cys-Arg/N-End Rule Pathway Is a General Sensor of Abiotic Stress in Flowering Plants. Current Biology doi: 10.1016/j.cub.2017.09.006

Open Access

Mike Holdsworth (University of Nottingham) is the corresponding author of this collaboration with colleagues from Sheffield, Spain and Taiwan that investigates how the N-rule degradation pathway acts a sensor of general abiotic stress in both Arabidopsis and Barley. These responses are integrated through degradation of the group VII Ethylene Response Factor transcription factors (ERFVIIs) family via direct and indirect pathways. In addition they link ERFVII activity with chromatin-remodeling ATPase BRAHMA providing evidence for a single mechanism that links the responses to a number of environmental signals.

Wang Y, Hills A, Vialet-Chabrand SR, Papanatsiou M, Griffiths H, Rogers S, Lawson T, Lew V, Blatt MR (2017) Unexpected Connections between Humidity and Ion Transport Discovered using a Model to Bridge Guard Cell-to-Leaf Scales. Plant Cell. doi: 10.1105/tpc.17.00694

Open Access

Mike Blatt (University of Glasgow) leads this collaboration with researchers at the Universities of Cambridge and Essex. They have developed the OnGuard2 quantitative systems platform that integrates numerous parameters that control guard cell dynamics across many scales including at molecular, cellular, tissue and canopy levels. They experimentally demonstrate that OnGuard2 faithfully reproduces the kinetics of real stomatal movement and therefore that this modeling is able to bridge the micro-macro divide.

Carter R, Sánchez-Corrales YE, Hartley M, Grieneisen VA, Marée AFM (2017) Pavement cells and the topology puzzle. Development. doi: 10.1242/dev.157073

Stan Maree and Veronica Griensien (John Innes Centre) lead this study that has looked at the patterning of 50000 Arabidopsis pavement cells to understand the topological signatures that exist in this population. They have developed a heuristic cellular division rule to produce a model that can reproduce their observations by predicting how these cells divide. They confirmed their model by tracking 800 mitotic events, allowing them to conclude that distinct topology is not a direct consequence of the jigsaw-like shape of the cells, but rather owes itself to life-history-driven process, with limited impact from cell surface mechanics.

Aston E, Channon A, Belavkin RV, Gifford DR, Krašovec R, Knight CG (2017) Critical Mutation Rate has an Exponential Dependence on Population Size for Eukaryotic-length Genomes with Crossover. Sci Rep. doi: 10.1038/s41598-017-14628-x

Open Access

In this study a team of computational biologists from Keele, Middlesex and Manchester have used Arabidopsis as an exemplar to understand how critical mutation rate (CMR) provides insights into the shift between survival-of-the-fittest and survival of individuals with greater mutational robustness. They have produced a simulation for these parameters that predicts outcomes for a range of biological organisms, showing that CMR decreases with reduced population size. They suggest that the model can be used to understand the conservation strategies exhibited in populations that are approaching extinction.

Farthing EC, Menguer PK, Fett JP, Williams LE (2017) OsMTP11 is localised at the Golgi and contributes to Mn tolerance. Sci Rep. doi: 10.1038/s41598-017-15324-6
Lorraine Williams (University of Southampton) and her colleagues have identified a transporter protein from rice, OsMTP11 that is involved in mangenase tolerance. They show that heterologous expression of this protein is able to rescue the manganese sensitive phenotype of Arabidopsis mtp11-3 knockouts. They show that OsMTP11 localises to the Golgi and have also conducted site directed mutagenesis to identify key residues that are important for the function of this protein.

Griffiths J, Catoni M, Iwasaki M, Paszkowski J (2017) Sequence-independent identification of active LTR retrotransposons in Arabidopsis. Mol Plant. doi: 10.1016/j.molp.2017.10.012

Open Access

Jerzy Paszkowski (SLCU) leads this single-figure short manuscript that has characterised the population of retrotransposons in Arabidopsis. They develop a novel cost-effective screening strategy that allows them to identify sequences found on extrachromosomal DNA (ecDNA), which includes a retroelement found in Lansberg erecta but not in the reference genome ecotype Col-0.

Arabdopsis Research Roundup: May 11th

by Geraint

Categories: Cardiff University, Essex University, GARNet, Global, Lancaster Unversity, Uncategorized, Warwick University

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Published on: May 11, 2017

This weeks Arabidopsis Research Roundup is lead by two papers that characterise the relationship between cell size and growth in different Arabidopsis tissues. Firstly the lab of GARNet PI Jim Murray look at how the cell cycle influences cell size progression in the SAM whilst George Bassel’s group from Birmingham investigate cell growth within a developing embryo. Thirdly is a paper from the University of Essex that further defines the role of the CP12 protein in control of photosynthesis. Next is a paper from researchers from the University of Warwick who lead a fascinating piece of rocket science that identifies differences in the vernalisation requirement across Brassica species whilst in the fifth paper, researchers from Lancaster identify environmentally defined QTLs that determine the plant response to glutamate. Finally is a paper that highlights a new software tool that has the self-explanatory title of the ‘UEA small RNA Workbench’ and is applicable for use with plant-derived datasets.

R Jones A, Forero-Vargas M, Withers SP, Smith RS, Traas J, Dewitte W, Murray JAH (2017) Cell-size dependent progression of the cell cycle creates homeostasis and flexibility of plant cell size. Nat Commun http://dx.doi.org/10.1038/ncomms15060

Open Access

This study comes from the lab of current GARNet PI Jim Murray at the Cardiff University. Lead author Angharad Jones kindly provides an audio description of the paper for the GARNet YouTube channel. This investigation looks at the factors that control the interaction between cell size and cell growth in a developing shoot meristem. They show that the dynamic regulation of this relationship is linked to the activity of two cyclin dependent kinases (CDKs) and that cell size is key in controlling the transition from G1>S and from G2>M phases of the cell cycle. Importantly this work uses precise imaging to track the progression of individual cell lineages and is therefore able to suggest that cell size is an emergent and not a directly determined property.

Souza NM, Topham AT, Bassel GW (2017) Quantitative analysis of the 3D cell shape changes driving soybean germination. J Exp Bot. http://dx.doi.org/10.1093/jxb/erx048

Open Access

George Bassel (University of Birmingham) leads this paper that uses information gained from the study of patterns of cell expansion in Arabidopsis embryos to investigate a similar process in soybean. Indeed as in Arabidopsis they show that there is preferential early cell expansion closest to the soybean radicle and that starting cell size corresponds to different growth rates. In addition they show that the growing hypocotyl has complex regulation and that differential ansiotrophy growth drives forward the process of germination. Ultimately they show that this occurs equivalently in both model and crop species.

Elena López-Calcagno P, Omar Abuzaid A, Lawson T, Anne Raines C (2017) Arabidopsis CP12 mutants have reduced levels of phosphoribulokinase and impaired function of the Calvin-Benson cycle. J Exp Bot http://dx.doi.org/10.1093/jxb/erx084 Open Access
This study from the photosynthesis group at the University of Essex is led by Tracey Lawson and GARNet committee member Christine Raines. They investigate the role of the CP12 multigene family that has three members in Arabidopsis. These are redox-sensitive proteins that facilitate the formation of a complex between glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and phosphoribulokinase (PRK) during the Calvin-Benson cycle. They show that plants with reduced levels of CP12-1 or CP12-2 have lower photosynthetic capacity and subsequently exhibit slower growth. The cell biological explanation for this alteration appears to focus on the PRK protein, which is present at lower levels in plants with reduced CP12-1 or CP12-2. Therefore the authors find that CP12-1 and CP12-2 are the key members of this gene family and they likely show functional redundancy in the tight control of photosynthesis.

Taylor JL, Massiah A, Kennedy S, Hong Y, Jackson SD (2017) FLC expression is down-regulated by cold treatment in Diplotaxis tenuifolia (wild rocket), but flowering time is unaffected. J Plant Physiol.

http://dx.doi.org/10.1016/j.jplph.2017.03.015 Open Access
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Steve Jackson (University of Warwick) leads this work that also features Chinese collaborators and investigates the role of FLOWERING LOCUS C (FLC) in the popular peppery salad plant Rocket (Diplotaxis tenuifolia) that, as a Brassica, is a somewhat closely related to Arabdopsis. The authors studied the vernalisation requirement in this plant so isolated its version of FLC, which was shown to functional compliment an Arabidopsis flc null mutant. However they showed that even though cold treatment reduced levels of DtFLC this did not alter the bolting time of the plant. This somewhat surprising result demonstrates that the link between FLC and flowering time is uncoupled in this species and that other mechanisms may take precedence, a situation different to that observed in Arabidopsis and other Brassicas.

Walch-Liu P, Meyer RC, Altmann T, Forde BG (2017) QTL analysis of the developmental response to L-glutamate in Arabidopsis roots and its genotype-by-environment interactions. J Exp Bot.

http://dx.doi.org/10.1093/jxb/erx132 Open Access Researchers from the groups of Brian Forde (Lancaster University) and Thomas Altmann (Leibniz Institute) collaborate in this research that identifies three novel QTLs (GluS1-3) that are involved in the response of Arabdopsis roots to external L-glutamate. When this experiment was extended they discovered that different environmental factors play a significant role in the control of this trait. The GluS1 locus is located on Chr3 yet is epistatically controlled by loci on Chr1 and Chr5 in response to temperatures. Overall this study demonstrates that the response to glutamate is controlled by multiple environmentally sensitive loci that vary between Arabidopsis ecotypes

Mohorianu I, Stocks MB, Applegate CS, Folkes L, Moulton V (2017) The UEA Small RNA Workbench: A Suite of Computational Tools for Small RNA Analysis. Methods Mol Biol.

http://dx.doi.org/10.1007/978-1-4939-6866-4_14

This manuscript from the University of East Anglia describes a set of software tools for the analysis of small RNAs. They used an Arabidopsis dataset to demonstrate the utility of the UEA small RNA Workbench, which can be found here: http://srna-workbench.cmp.uea.ac.uk/

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Arabidopsis Research Roundup: February 9th

by Geraint

Categories: Arabidopsis, CPIB, Essex University, Exeter University, Global, Rothamsted Research, University of Sheffield, Warwick University

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Published on: February 9, 2016

It has been a quiet couple of weeks for newly published UK Arabidopsis Research but what might be lacking in quantity is made up for in quality! Firstly the PRESTA consortium use gene regulatory network analysis to identify a key component in the response to drought stress. Secondly is a paper featuring researchers from Rothamstead that identifies a new molecular participant in the control of RNA surveillance. Thirdly is a paper that investigates the function of aquaporins during lateral root emergence and includes researchers from Warwick and Nottingham. Finally is a study from Sheffield that investigates necrotropic and biotropic strategies employed by an ascomycete pathogen. It is also nice to observe that each of these papers are open access.

Bechtold U, Penfold CA, Jenkins DJ, Legaie R, Moore JD, Lawson T, Matthews JS, Vialet-Chabrand SR, Baxter L, Subramaniam S, Hickman R, Florance H, Sambles C, Salmon DL, Feil R, Bowden L, Hill C, Baker NR, Lunn JE, Finkenstadt B, Mead A, Buchanan-Wollaston V, Beynon JL, Rand DA, Wild DL, Denby KJ, Ott S, Smirnoff N, Mullineaux PM (2016) Time-series transcriptomics reveals that AGAMOUS-LIKE22 links primary metabolism to developmental processes in drought-stressed Arabidopsis Plant Cell http://dx.doi.org/10.1105/tpc.15.00910 Open Access

This Large Scale Biology article is the result of the PRESTA collaboration that is based at the Universities of Essex, Exeter and Warwick. The research plan of the PRESTA project is based upon the generation of large scale transcriptomic datasets and in this case they investigate changes in gene expression in plants subjected to drought stress. They identified over 1800 differentially expressed genes and the early changes coincided with a drop in carbon assimilation together with a late increase in foliar ABA content. Using Bayesian network modelling of differentially expressed transcription factors they identified the AGAMOUS-LIKE22 (AGL22) gene as a key component in this gene regulatory network. AGL22 had been previously found to play an important role in the change from vegetative to floral development but in this context it influences photosynthetic rates and lifetime water use.

Hématy K, Bellec Y, Podicheti R, Bouteiller N, Anne P, Morineau C, Haslam RP, Beaudoin F, Napier JA, Mockaitis K, Gagliardi D, Vaucheret H, Lange H, Faure JD (2016) The Zinc-Finger Protein SOP1 Is Required for a Subset of the Nuclear Exosome Functions in Arabidopsis PLoS Genetics 12(2):e1005817 http://dx.doi.org/10.1371/journal.pgen.1005817 Open Access

This Franco-US collaboration also includes a contribution from Johnathan Napier’s group at Rothamstead Research. They investigated the function of the essential Arabidopsis PASTICCINO2 (PAS2) gene by isolating three suppressors of pas2 mutants (termed sop mutants). PAS2 is involved in correct splicing so the sop mutants prevented degradation of mis-spliced pas2 mRNA species. The suppressor genes were either previously characterized as being involved with function of the exosome (SOP2/RRP4, SOP3/HEN2) or as a novel zinc-finger protein (SOP1) that colocalised with HEN2 in nucleoplasmic loci. The authors show additional evidence suggesting that the SOP proteins are involved in RNA quality control and introduce SOP1 as a novel component that is involved in nuclear RNA surveillance.

Reinhardt H, Hachez C, Bienert MD, Beebo A, Swarup K, Voss U, Bouhidel K, Frigerio L, Schjoerring JK, Bennett MJ, Chaumont F (2016) Tonoplast aquaporins facilitate lateral root emergence Plant Physiology. http://dx.doi.org/10.1104/pp.15.01635 Open Access

This Belgian-led study includes lead-UK representation from Warwick (Lorenzo Frigerio) and Nottingham (Malcolm Bennett) and investigates the role of tonoplast-localised aquaporin proteins during lateral root emergence. The AtTIP1;1, AtTIP1;2 and AtTIP2;1 are abundant aquaporin proteins and the triple tip mutant shows a reduction in lateral root (LR) number without having a shorter primary root. This effect is not due to a reduction of LR primordia but rather due to a defect in the elongation of emerging LR. The authors show that spatial and temporal variations of TIP isoform expression throughout the root correlates with the tip mutant phenotype. Surprisingly, native expression of TIP2:1, which is found only at the base of the LR, can restore wildtype LR emergence to the triple mutant, suggesting that aquaporin activity in this region is sufficient to set-off LR outgrowth.

Pétriacq P, Stassen JH, Ton J (2016) Spore density determines infection strategy by the plant-pathogenic fungus Plectosphaerella cucumerina Plant Physiology http://dx.doi.org/10.1104/pp.15.00551 Open Access

Jurriaan Ton (Sheffield) is the lead researcher on this study that investigates the molecular factors that allow pathogens to switch between necrotropy and biotrophy, which elicit different response pathways within the infected plant. They used untargeted metabolomics to investigate the growth of the ascomycete pathogen Plectosphaerella cucumerina on Arabidopsis leaves. Higher spore densities activate a JA-dependent necrotropic defence response whilst lower spore numbers causes hemi-biotrophic SA-dependent responses. This change is reflected in the susceptibility of different Arabidopsis mutants to differing spore densities and allow the authors to conclude that P. cucumerina is able to gain an advantage over the host immunity by switching between different modes of infection.

Arabidopsis Research Roundup: January 22nd 2016

by Geraint

Categories: Arabidopsis, bioinformatics, Cambridge University, Essex University, Global, Light Signaling, University of Leeds, University of Southampton, University of York

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Published on: January 22, 2016

A mixed selection of research in this UK Arabidopsis Roundup. Firstly a study from Stefan Kepinski and Mark Estelle that adds another layer of understanding to the regulation of the auxin response. Enrique Lopez-Juez leads a study into signaling between the nucleus and chloroplast while Tracey Lawson contributes to an investigation into role of starch metabolism in guard cells. Fran Maathuis and co-worker looks at differences in vacuolar transport between Arabidopsis ecotypes while Alan Marchant is involved in a study of cell wall pectins. Finally William Amos has uses the 1001genomes project to investigate heterozygote instability (HI).

Wang R, Zhang Y, Kieffer M, Yu H, Kepinski S, Estelle M (2016) HSP90 regulates temperature-dependent seedling growth in Arabidopsis by stabilizing the auxin co-receptor F-box protein TIR1. Nat Commun. 5;7:10269. http://dx.doi.org/10.1038/ncomms10269 Open Access

Stefan Kepinski (Leeds) is the UK lead on this collaboration with Mark Estelle from UCSD and it continues their previous work that investigates the much-studied auxin receptor TIR1. Arabidopsis seedlings grown at 29C show auxin-dependent hypocotyl elongation although the molecular mechanism behind this response has remained opaque. In this study they show that in high temperatures TIR1 accumulates in a manner dependent on the molecular chaperone, HSP90. In addition HSP90 and the co-chaperone SGT1 directly interact with TIR1. Inhibition of HSP90 results in degradation of the TIR1 and causes a range of auxin-mediated growth processes at both high and low temperatures. This study adds another level of complexity to the molecular basis of the auxin response.

Hills AC, Khan S, López-Juez E (2015) Chloroplast Biogenesis-Associated Nuclear Genes: Control by Plastid Signals Evolved Prior to Their Regulation as Part of Photomorphogenesis. Front Plant Sci. 10;6:1078. http://dx.doi.org/10.3389/fpls.2015.01078 Open Access

The work comes exclusively from the lab of Enrique Lopez-Juez at Royal Holloway and investigates at the expression of photosynthesis-associated nuclear genes (PhANGs). This expression is dependent on light as well as plastid-to-nucleus “biogenic” communication signals and causes the assembly of photosynthesis component chloroplasts. The authors investigate the factors that control the activity of the Lhcb promotor in the light and the dark, both in angiosperms and gymnosperms. They propose that suppression of PhANG responses has contributed to the evolution of light-controlled chloroplast biogenesis.

Horrer D, Flütsch S, Pazmino D, Matthews JS, Thalmann M, Nigro A, Leonhardt N, Lawson T, Santelia D (2015) Blue Light Induces a Distinct Starch Degradation Pathway in Guard Cells for Stomatal Opening. Current Biology http://dx.doi.org/10.1016/j.cub.2015.12.036

Tracey Lawson (University of Essex) is the UK lead on this UK-French-Swiss study that uses the stomatal guard cell experimental system to investigate the role of carbon metabolism in the response to blue light. Interestingly guard cells differ from other leave tissues in that they contain starch at the end of the night. However this starch store is rapidly degraded within 30minutes of light and is important for stomatal opening and subsequent biomass production. This starch degradation involves action of two enzymes, β-amylase 1 (BAM1) and α-amylase 3 (AMY3) that do not function during night time starch degradation in other tissues. This process is coordinated by blue light signalling and correlates with the activity of a plasma membrane ATPase. This study adds yet another level of our understanding into the mechanism of stomatal opening. See image for a proposed model of this process (from Cell Press).

Hartley TN, Maathuis FJ (2015) Allelic variation in the vacuolar TPK1 channel affects its calcium dependence and may impact on stomatal conductance. FEBS Lett. 90(1):110-7 http://dx.doi.org/10.1002/1873-3468.12035

Fran Maathuis (University of York) is the leader on this study that assesses the transport properties of two different vacuolar-localised AtTPK1 alleles identified for a study of natural variation in Arabidopsis. They use patch-clamping the interrogate the difference between these proteins from Lansberg (Ler) and Kas-2 ecotypes, when they showed different levels of Ca(2+) dependence. This coincided with lower water loss in either the presence of absence of ABA and higher Ler AtTPK1 activity at similar cytoplasmic [Ca]. The authors present a model that helps to explain their findings.

Dumont M, Lehner A, Vauzeilles B,, Malassis J, Marchant A, Smyth K, Linclau B, Baron A, Mas Pons J, Anderson CT, Schapman D, Galas L, Mollet JC, Lerouge P (2015) Plant cell wall imaging by metabolic click-mediated labelling of rhamnogalacturonan II using azido 3-deoxy-D-manno-oct-2-ulosonic acid. Plant Journal. http://dx.doi.org/10.1111/tpj.13104

The majority of the authors on this Technical Advance are from French institutions but also includes UK plant scientist Alan Marchant (University of Southampton). They investigate the chemistry of Arabidopsis and tobacco cell walls, specifically looking at the incorperation of 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo), a monosaccharide that is only found the cell wall pectin rhamnogalacturonan-II (RG-II). They show that RG-II is found in the primary cell wall including within the root elongation zone. Finally they show that monitoring of Kdo is an effective way to study the synthesis and redistribution of RG-II during root growth.

Amos W (2015) Heterozygosity increases microsatellite mutation rate. Biol Lett. http://dx.doi.org/10.1098/rsbl.2015.0929 Open Access

This study is led by Professor William Amos who is based in the Zoology department at Cambridge. He is not usually a plant science researcher but used the excellent 1001genome project to investigate heterozygote instability (HI) in Arabidopsis. He looked at AC microsatellite sequences from over 1100 genome sequences and used rare alleles as a surrogate for more recent mutations, ultimately showing that rare alleles are more likely to occur at locus-population combinations with higher heterozygosity even when all populations carry exactly the same number of alleles. This shows that local heterozygosity causes more mutations and represents a positive feedback loop.

Arabidopsis Research Roundup: January 8th

by Geraint

Categories: Arabidopsis, Audio, Durham University, epigenetics, Essex University, GARNet, Global, John Innes Centre, Oxford Brookes University, plant pathogens, Uncategorized, University of Oxford

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Published on: January 8, 2016

For the inaugural Arabidopsis Research Roundup of 2016 we feature the final publications of UK researchers from 2015. Martin Howard kindly provides an audio description of a paper that looks at a fundamental aspect of transcriptional regulation, through the lense of the FLC gene, whilst his co-author Caroline Dean on that paper is an author on another manuscript that investigates RNA stability in the same FLC locus. Katja Graumann leads a paper that looks into gene expression at the periphery of the nucleus whilst Ian Colbeck looks at the effect of silver nanoparticles on plant growth. Ari Sadanandom is the UK lead of a study that investigates of SUMOylation and Ian Fricker looks at the role of a cytochrome P450 on the defence response. Finally Liam Dolan is involved in a comparative analysis of the genes involved in tip growth in the cells of plants and moss.

Wu Z, Ietswaart R, Liu F, Yang H, Howard M, Dean C (2015) Quantitative regulation of FLC via coordinated transcriptional initiation and elongation. Proc Natl Acad Sci U S A. http://dx.doi.org/10.1073/pnas.1518369112 Open Access

Martin Howard and Caroline Dean lead this study that comes out of the John Innes Centre and is the result of the same collaboration that featured in an ARR earlier in 2015. In this study they investigate the mechanisms that control the quantitative regulation of gene expression by focusing on the complex regulation of the FLOWERING LOCUS C (FLC). FLC expression is controlled by a chromatin silencing mechanism involving alternative polyadenylation of antisense transcripts. However they surprisingly show that the amount of RNA Polymerase II occupancy at FLC does not coincide very well with levels of FLC transcription. They used modeling to predict that there is a tight coordination between transcriptional initiation and elongation, which was validated by detailed measurements of the levels of FLC intronic RNA. Variation within initiation and elongation rates were significantly different and was coincident with changes in H3K36me3 and H3K4me2 levels in the FLC gene. The authors propose that chromatin state can influence transcriptional initiation and elongation rates and may be a general mechanism for quantitative gene regulation in a chromatin context.

Martin Howard kindly provides an audio description of this paper and wider aspects of transcriptional regulation.

Wu Z, Zhu D, Lin X, Miao J, Gu L, Deng X, Yang Q, Sun K, Zhu D, Cao X, Tsuge T, Dean C, Aoyama T, Gu H, Qu LJ (2015) RNA-binding proteins At RZ-1B and At RZ-1C play a critical role in regulation of pre-mRNA splicing and gene expression during Arabidopsis development Plant Cell http://dx.doi.org/10.1105/tpc.15.00949

This study investigates a set of previously mysterious RNA-binding proteins and is led by Chinese researchers with a UK contribution from Caroline Dean (JIC). They look at two Arabidopsis proteins, AtRZ-1B and At RZ-1C that have RNA-binding domains and are localised to the mysterious nuclear speckles. In addition these proteins physically interact with a range of serine/arginine-rich (SR) proteins and disrupting this binding causes a range of growth phenotypes that are similar to that observed in At rz-1b/At rz-1c double mutants. These include delayed seed germination, reduced stature, and serrated leaves and on the cellular level this is accompanied by defective splicing and global changes in gene expression. Interestingly AtRz-1C directly effects the expression of the floral repressor FLC, which links this work with other research in the Dean lab. Overall this highlights the important role of At RZ-1B/1C in RNA splicing and the link to many developmental phenotypes.

Smith S, Galinha C, Desset S, Tolmie F, Evans D, Tatout C, Graumann K (2015) Marker gene tethering by nucleoporins affects gene expression in plants. Nucleus. http://dx.doi.org/10.1080/19491034.2015.1126028

Expression of Seh1-LacI-YFP at the nuclear periphery. From http://dx.doi.org/10.1080/19491034.2015.1126028

Katja Graumann and David Evans (Oxford Brookes) are the lead academics on this collaboration with the lab of Christophe Tatout from Clermont Ferrand in France. They are attempting to answer a long standing question in the field of the biology of the nucleus; whether genes that are located close to nuclear pore complexes have increased gene expression. They used the Lac Operator/ Lac Repressor (LacI-LacO) system to assess changes in gene expression when a loci is tethered to the NPC by attaching the LacI domain to the nucleoporins Seh1 or NUP50a. The Seh1 clones localised to the nuclear periphery and showed higher RNA and protein expression of Luc. When this interaction at the periphery was distributed, the higher levels of expression were abolished. The authors therefore show that association with the nuclear periphery is important for the regulation of gene expression.

Sosan A, Svistunenko D, Straltsova D, Tsiurkina K, Smolich I, Lawson T, Subramaniam S, Golovko V, Anderson D, Sokolik A, Colbeck I, Demidchik V (2015) Engineered silver nanoparticles are sensed at the plasma membrane and dramatically modify physiology of Arabidopsis thaliana plants. Plant Journal http://dx.doi.org/10.1111/tpj.13105

Ian Colbeck (Essex) is the UK lead on this study that involves a collaboration between researchers in New Zealand, Belarus and Russia and focuses on the effect of silver nanoparticles (Ag NPs) on the growth of Arabidopsis seedlings. This type of nanoparticle is used for many difference applications so worries exist about the safety of their use. This study looks at the effect of Ag NPs on Arabidopsis root elongation and leaf expansion, both of which were inhibited at over [300mg/l] Ag NPs. In addition there were reductions of photosynthetic efficiency and accumulation of silver in plant tissues. They also showed that these particles altered the influx and efflux of metal ions whilst, although they were unable to catalyse hydroxyl radical generation, they did directly oxidise the major plant antioxidant, L-ascorbic acid. Overall the authors show that silver nanoparticles induce classical stress signalling responses but also illicit specific detrimental effects at the plasma membrane. At the whole plant level this study provides a worrying example for the role of Ag NPs on whole plant growth, even though the concentrations used in food preparation might be lower.

Crozet P, Margalha L, Butowt R, Fernandes N, Elias A, Orosa B, Tomanov K, Teige M, Bachmair A, Sadanandom A, Baena-González E (2015) SUMOylation represses SnRK1 signaling in Arabidopsis. Plant Journal http://dx.doi.org/10.1111/tpj.13096

This pan-European study features researchers from Portugal, Austria and the UK’s Durham University, led by Ari Sadanandom. They investigate the role of the SnRK1 protein kinase, which is a key enzyme for modulating the plant stress response. This paper adds detail to the cellular mechanisms that regulate SnRK1 and they show that SnRK1 is SUMOylated by the SIZ1 E3 SUMO ligase. SnRK1 is ubiquitinated and degraded in a SIZ1-dependent manner that is lacking in siz1 mutants. Interestingly only active SnRK1 is degraded as the inactive SnRK1 protein is stable but can be easily degraded upon SUMOylation. Finally they show that SnRK1 is involved in a negative feedback loop wherein it controls its own SUMOylation and degradation that, in wildtype cells, prevents a potentially detrimental stress response.

Fuchs R, Kopischke M, Klapprodt C, Hause G, Meyer AJ, Schwarzländer M, Fricker MD, Lipka V (2015) Immobilized subpopulations of leaf epidermal mitochondria mediate PEN2-dependent pathogen entry control in Arabidopsis. Plant Cell http://dx.doi.org/10.1105/tpc.15.00887

Mark Fricker (Oxford) is the UK research lead on this study that investigates the role of the atypical myrosinase PEN2 in the response to pathogen attack. PEN2 is targeted to both peroxisomes and mitochondria and can also form homo-oligomer complexes. PEN2 localised to mitochondria are immobilized following fungal invasion and this accompanies mitochondrial arrest. The substrate for PEN2 is produced by the cytochrome P450 monooxygenase CYP81F2, which is localized to the ER and moves toward immobilized mitochondria. The critical function of PEN2 in that organelle was confirmed by the result that showed exclusive mitochondria targeting could rescue pen2 mutant phenotypes. The authors show by live-cell imaging that arrested mitochondria in domains of plant-microbe interaction exhibit a pathogen-induced redox imbalance that may lead to production of intracellular signals.

Ortiz-Ramírez C, Hernandez-Coronado M, Thamm A, Catarino B, Wang M, Dolan L, Feijó JA, Becker JD (2015) A transcriptome atlas of Physcomitrella patens provides insights into the evolution and development of land plants. Mol Plant. http://dx.doi.org/10.1016/j.molp.2015.12.002

Liam Dolan (Oxford) is an author on this study that is led from Portugal and is an investigation of the transcriptome of the model moss Physcomitrella patens throughout its life cycle. They also compare transcriptomes from P.patens and Arabidopsis, allowing the authors to identify transcription factors that are expressed in tip growing cells. Interestingly they identified differences in expression patterns that might account for the differences between tip growth in moss and the Arabidopsis root hairs, an area that is the expertise of the Dolan lab.

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Arabidopsis Research Roundup: December 18th

by Geraint

Categories: Arabidopsis, Audio, Brassica, Cambridge University, CPIB, Durham University, Edinburgh University, epigenetics, Essex University, GARNet, Global, John Innes Centre, Oxford University, Plos One

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Published on: December 18, 2015

The final Arabidopsis Research Roundup of 2015 contains a bumper crop of papers that again highlights the diversity of research occuring in UK plant science. Justin Goodrich from the University of Edinburgh kindly provides an audio description of work that identifies a novel role for a member of a transposon gene family. Elsewhere are studies about a specific aspect of the biochemistry of crytochromes as well as confirmation of a role for DNA gyrases in Arabidopsis. Paul Dupree (Cambridge) leads a study into the mechanism of ascorbic acid production while Heather Knight is the UK representative in a study about cell wall composition. We also present an investigation into the mechanism and subsequent expression changes that occur following infection with different isolates of the Turnip Mosaic Potyvirus. Finally are two short studies from Ive de Smet (Nottingham) and Matt Jones (Essex).

Liang SC, Hartwig B, Perera P, Mora-García S, de Leau E, Thornton H, de Alves FL, Rapsilber J, Yang S, James GV, Schneeberger K, Finnegan EJ, Turck F, Goodrich J (2015) Kicking against the PRCs – A Domesticated Transposase Antagonises Silencing Mediated by Polycomb Group Proteins and Is an Accessory Component of Polycomb Repressive Complex 2. PLoS Genet. 11 e1005660. http://dx.doi.org/10.1371/journal.pgen.1005660 Open Access

Justin Goodrich (Edinburgh) is the lead of this collaborative study between UK, German and Australian researchers that investigates the role of the evolutionarily conserved Polycomb group (PcG) and trithorax group (trxG) genes during plant development. These homeotic genes influence gene expression by causing epigenetic chromatin changes, usually in the form of histone methylation. Previously the ANTAGONIST OF LIKE HETEROCHROMATIN PROTEIN1 (ALP1) gene was found to act as a genetic suppressor the Arabidopsis PcG gene, LIKE HETEROCHROMATIN PROTEIN1 (LHP1). In this study ALP1 is shown to genetically interact with members of these two gene families and its activity is necessary for the activation of several floral homeotic genes. Surprisingly the ALP1 gene is shown to encode for a transposase of the PIF/Harbinger class, which is conserved throughout land plants. The authors suspect that the transposase activity has been lost in the angiosperm lineage, where the gene obtained a novel function. Interestingly ALP1 can interact with the core PrC complex, which most notably participates in H3K27me3 methylation and therefore appears to act, along with other proteins such as EMBRYONIC FLOWER 1 (EMF1), as a plant-specific accessory component that controls histone modification. The authors speculate that this novel function might have arisen as a “means for the cognate transposon to evade host surveillance or for the host to exploit features of the transposition machinery beneficial for epigenetic regulation of gene activity”. Over the coming years it will be interesting to discover if other transposon-encoded genes share novel functions and this study represents an important lesson for researchers not to ignore transposon sequences as ‘junk’ DNA that they might feel can clutter up their analysis!

Justin Goodrich kindly provides an audio summary of this paper:

van Wilderen LJ, Silkstone G, Mason M, van Thor JJ, Wilson MT (2015) Kinetic studies on the oxidation of semiquinone and hydroquinone forms of Arabidopsis cryptochrome by molecular oxygen FEBS Open Bio. 5:885-892 http://dx.doi.org/10.1016/j.fob.2015.10.007 Open Access

This study is a collaborative effort between researchers from Imperial College and the University of Essex, led by emeritus biochemistry Professor Michael Wilson and is an in vitro analysis of the oxidation of the Arabidopsis cryptochrome (CRY) photoreceptor in the presence and absence of an external electron donor. They show that a more complex model than previously thought is required to explain the mechanism by which the CRY-associated flavin molecule is oxidised. The authors propose that the final steps in this reaction require cooperative interaction between partners in a CRY homodimer or between separate CRY molecules.

Evans-Roberts KM, Mitchenall LA, Wall MK, Leroux J, Mylne JS, Maxwell A (2015) DNA Gyrase is the Target for the Quinolone Drug Ciprofloxacin in Arabidopsis thaliana. J Biol Chem. http://dx.doi.org/10.1074/jbc.M115.689554 Open Access

Antony Maxwell from the Biological Chemistry department from the John Innes Centre is the UK academic lead on this UK-Australian study. This group has previously shown that Arabidopsis contains three proteins thought to function as DNA Gyrases (AtGYRA, ATGYRB1, ATGYRB2) although they could not provide direct evidence that are were involved in DNA supercoiling. This study moves the work on by identifying mutant plants that are resistant to the drug ciprofloxacin and contain a point mutation in AtGYRA. Furthermore ATGYRA heterologously expressed in insect cells has supercoiling activity. Therefore the authors unequivocally show that plants encode an organellar-targeted DNA gyrase that, like bacterial gyrases, is a target for ciprofloxacin. This work has important consequences for our understanding of plant physiology and in the future development of novel herbicides.

Sawake S, Tajima N, Mortimer JC, Lao J, Ishikawa T, Yu X, Yamanashi Y, Yoshimi Y, Kawai-Yamada M, Dupree P, Tsumuraya Y, Kotake T (2015) KONJAC1 and 2 Are Key Factors for GDP-Mannose Generation and Affect l-Ascorbic Acid and Glucomannan Biosynthesis in Arabidopsis The Plant Cell http://dx.doi.org/10.1105/tpc.15.00379

Paul Dupree (Cambridge) is the British lead on the UK-Japanese collaboration that investigates the role of the GDP-mannose pyrophosphorylase (GMPP), VITAMIN C DEFECTIVE1 (VTC1) enzyme in catalysis of the rate-limiting step in the production of ascorbic acid (AsA). They identify two novel pyrophosphorylase-like proteins, KONJAC1 (KJC1) and KJC2 that stimulate VTC1. Mutant analysis showed that these proteins are necessary for normal growth that coincides with control of AsA production via stimulating GMPP activity. Yeast 2 Hybrid analysis is indicative of a direct interactin between KJC and VTC1 proteins. In future, it will be interesting to investigate the role of these proteins in plants that are more relevant to human consumption of AsA.

Sorek N, Szemenyei H, Sorek H, Landers A, Knight H, Bauer S, Wemmer DE, Somerville CR (2015) Identification of MEDIATOR16 as the Arabidopsis COBRA suppressor MONGOOSE1. PNAS http://dx.doi.org/10.1073/pnas.1521675112

Heather Knight (Durham) is the sole UK representative on this manuscript that is led by the lab of Chris Somerville from the University of California. In this work the authors identified suppressors of the Arabidopsis cobra mutant, which have defects in cellulose formation. The appropriately named mongoose (mon1) mutant partially restored cellulose levels and also restored the esterification ratio of pectin to wild-type levels. MON1 was cloned to the MEDIATOR16 (MED16)/ SENSITIVE TO FREEZING6 (SFR6) locus and single mon1 mutants are resistant to cellulose biosynthesis inhibitors. Concomitantly, transcriptome analysis demonstrated that a set of ‘cell wall’ genes are misregulated in mon1/med16/sfr6, including two encoding pectin methylesterase inhibitors. Overall the authors suggest that cellulose biosynthesis is closely linked to esterification levels of pectin and offer a number of possible explanations for this functional relationship.

Sánchez F, Manrique P, Mansilla C, Lunello P, Wang X, Rodrigo G, López-González S, Jenner C, González-Melendi P, Elena SF, Walsh J, Ponz F (2015) Viral Strain-Specific Differential Alterations in Arabidopsis Developmental Patterns Mol Plant Microbe Interact. http://dx.doi.org/10.1094/MPMI-05-15-0111-R

The UK contributor to this Spanish-led study is Carol Jenner, who at the time was a research fellow at the University of Warwick. This study highlights the morphological changes that occur in Arabidopsis plants infected by different isolates of Turnip mosaic virus (TuMW). The UK1 and JPN1 versions of TuMW were shown to have highest levels of sequence divergence in the P3 cistron and following the generation and use of viral chimeras, it is this region that was identified as the major viral determinant of plant developmental changes. However when the P3 gene was constitutively expressed in Arabidopsis it did not cause any development effects, which highlights the importance of performing infection studies in a whole-plant context. Latterly the authors performed transcriptomic and interactomic analysis, showing that infection with the most severe UK1 strain primarily causes changes, perhaps unsurprisingly, in genes involved in transport and in the stress response.

Czyzewicz N, De Smet I (2015) The Arabidopsis thaliana CLAVATA3/EMBRYO-SURROUNDING REGION 26 (CLE26) peptide is able to alter root architecture of Solanum lycopersicum and Brassica napus. Plant Signal Behav http://dx.doi.org/10.1080/15592324.2015.1118598

This work was performed in the lab of Ive De Smet, who is a BBSRC research fellow at the University of Nottingham. In this short communication they show that overexpression of the Arabidopsis AtCLE26 peptide is able to induce architectural change in the agriculturally important crops, Brassica napus and Solanum lycopersicum. Having previously shown that AtCLE26 is similarly active in Arabidopsis, Brachypodium and Triticum, these experiments further demonstrate that small peptide signaling plays an important role in root development across plant lineages.

Litthauer S1, Battle MW1, Jones MA (2015) Phototropins do not alter accumulation of evening-phased circadian transcripts under blue light. Plant Signal Behav. http://dx.doi.org/10.1080/15592324.2015.1126029

Matt Jones (Essex) leads this accompanying study to the more substantial project previously published in Plant Journal. This manuscript reports that phototropin photoreceptors are not involved in the nuclear accumulation of evening-phased circadian transcripts. In addition they show that even in phototropin mutants, the rhythms of nuclear clock transcript accumulation are maintained under fluctuating light regimes.

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