Arabidopsis Research Report: May 26th

This weeks Arabidopsis Research Roundup includes six studies across a range of discplines. Firstly Alison Smith provides an excellent audio description of an investigation into the dynamics of night-time starch degradation.

Secondly three UK institutions (Durham, Exeter and Oxford Brookes) participate in a study of VAP27 membrane network proteins. Next a broad collaboration from CPIB in Nottingham then introduce a multi-scale model that helps describe Arabidopsis root development.

We also include two studies that involve collaborations with Korean researchers: Gary Loake is a contributor on a study that introduces plant RALF genes whilst Ian Henderson’s research group participates in a study into the function of the SWR1 complex in miRNA gene expression. Finally we highlight a new Plant Cell teaching tool put together by UK academics from Hull and Bristol.

Feike D, Seung D, Graf A, Bischof S, Ellick T, Coiro M, Soyk S, Eicke S, Mettler-Altmann T, Lu KJ, Trick M, Zeeman SC, Smith AM (2016) The starch granule-associated protein EARLY STARVATION1 (ESV1) is required for the control of starch degradation in Arabidopsis thaliana leaves Plant Cell

http://dx.doi.org/10.1105/tpc.16.00011 Open Access

This UK and Swiss study is led by Alison Smith from the John Innes Centre and investigates starch degradation that occurs during nighttime. They developed a novel screen to identify an uncharacterized mutant called early starvation 1 (esv1) that more rapidly degraded starch so that it is exhausted earlier in the night. They found that ESV1 and the related LESV1 proteins associated with starch granules within the chloroplast stroma. The authors propose that these proteins influence the organisation of the starch granule matrix, facilitating access for starch-degrading enzymes. In addition they also show that this function appears to be conserved throughout all starch-synthesizing organisms.

Professor Smith provides an audio description of this paper:

Wang P, Richardson C, Hawkins TJ, Sparkes I, Hawes C, Hussey PJ (2016) Plant VAP27 proteins: domain characterization, intracellular localization and role in plant development. New Phytol. 210(4):1311-1326 http://dx.doi.org/10.1111/nph.13857

This cell biology-focused study is a collaboration between the Universities of Exeter, Durham and Oxford Brookes and investigates vesicle-associated membrane protein-associated proteins (VAPs), which form part of the network that links the plasma membrane and ER. The Arabidopsis genome contains 10 VAP homologues (VAP27-1 to -10) split into 3 clades. Members of clades I and II localise to both ER as well as to ER/PM contact sites (EPCSs) whilst clade II members are only found at the PM, all discovered through transient expression experiments in tobacco. Interestingly the localisation to the EPCSs is associated with the cytoskeleton but does not require the presence of that underlying structure. These proteins are expressed in most cell types and when their levels are altered, plants show pleiotropic phenotypes. Overall this study shows that VAP27 proteins are required for ER-cytoskeleton interactions that are critical for normal plant development.

Muraro D, Larrieu A, Lucas M, Chopard J, Byrne H, Godin C, King J (2016) A multi-scale model of the interplay between cell signalling and hormone transport in specifying the root meristem of Arabidopsis thaliana. J Theor Biol. S0022-5193(16)30070-4 http://dx.doi.org/10.1016/j.jtbi.2016.04.036

From http://dx.doi.org/10.1016/j.jtbi.2016.04.036

This investigation was performed at CPIB in Nottingham in collaboration with the Virtual Plant Project in Montpellier and is led by John King. The authors have developed a multi-scale computational model that allows the study of signalling networks that occurs during Arabidopsis root growth. This model was experimentally tested to investigate how it is affected by hormonal changes during root growth. The model was able to identify two novel mutants that significantly alter root length through perturbations in meristem size. In general this study demonstrates the value of multi-scale modeling as part of the process of evaluating the function of the components that define the formation of the root meristem.

Sharma A, Hussain A, Mun BG, Imran QM, Falak N, Lee SU, Kim JY, Hong JK, Loake GJ, Ali A, Yun BW (2016) Comprehensive analysis of plant rapid alkalization factor (RALF) genes Plant Physiol Biochem. 106:82-90

http://dx.doi.org/10.1016/j.plaphy.2016.03.037

This Korean-led study includes a contribution from Gary Loake from the University of Edinburgh and is the first comprehensive investigation of Rapid alkalization factor (RALF) proteins across plant species. These RALF proteins are thought to be important signalling molecules in plant defense and development. This study provides information on gene structure, subcellular locations, conserved motifs, protein structure, protein-ligand interactions and promoter analysis across Arabidopsis, rice, maize and soybean. The RALF genes are phylogenetically divided into 7 clades and their mRNA upregulation following nitrosative and oxidative stresses suggests that they are function in responding to changes in cellular redox status. Overall this manuscript provides a valuable resource to prime future research into the role of RALF genes.

Choi K, Kim J, Müller SY, Oh M, Underwood C, Henderson I, Lee I (2016) Regulation of microRNA-mediated developmental changes by the SWR1 chromatin remodeling complex in Arabidopsis thaliana. Plant Physiol. http://dx.doi.org/10.1104/pp.16.00332

GARNet committee member Ian Henderson (Cambridge) is a contributor on this study that is led by researchers in Seoul, South Korea. In the last ARR, Vinod Kumar described work that looked into the role of the SWR1 chromatin-remodeling complex and this study provides an insight into the role of this same SWR1 complex on microRNA (miRNA)-mediated transcriptional control. In SWR1 complex mutants (arp6, sef, and pie1), deep sequencing revealed that many miRNA types and their target mRNAs are misregulated. This further establishes the role of the SWR1 complex in the control of nucleosome occupancy, likely by mediating the exchange of H2A isoforms, for a range of genes involved in the fine-tuning of numerous developmental processes.

Hubbard, K, Dodd, A. (2016). Rhythms of Life: The Plant Circadian Clock. Teaching Tools in Plant Biology: Lecture Notes. http://dx.doi.org/10.1105/tpc.116.tt0416

Katherine Hubbard and Anthony Dodd have produced a teaching resource focused on the Circadian Clock as part of the increasingly comprehensive Plant Cell Teaching Tools. Most academics are looking to save time and this resource will allow them to do this and provides excellent coverage of the topic.

Arabidopsis Research Roundup: May 13th

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Published on: May 13, 2016

This weeks Arabidopsis Research Roundup includes two peer-reviewed papers and the release of a preprint. Vinod Kumar from the JIC provides an audio description of a study that investigates the role of the SWR1 complex in the defence response. Secondly Jessica Metcalf from Oxford is a contributor on a study that looks at population responses of Arabidopsis to simulated climate change. Finally John Brown (University of Dundee and the James Hutton Institute) is the corresponding authors on a preprint that introduces a new Arabidopsis transcriptome annotation.

Berriri S, Gangappa SN, Kumar SV (2016) SWR1 chromatin-remodelling complex subunits and H2A.Z have non-overlapping functions in immunity and gene regulation in Arabidopsis Molecular Plant http://dx.doi.org/10.1016/j.molp.2016.04.003 Open Access

Vinod Kumar (John Innes Centre) is the corresponding author on this study that investigates the incorporation of the histone variant H2A.Z into Arabidopsis nucleosomes. This histone variant is important in the control of differential gene expression although its role in plant immunity is not well understood. H2A.Z is integrated into nucleosome by the SWR1 chromatin remodelling complex that contains a number of subunits namely PHOTOPERIOD-INDEPENDENT EARLY FLOWERING1 (PIE1), ACTIN-RELATED PROTEIN6 (ARP6), and SWR1 COMPLEX 6 (SWC6). Interestingly each subunit plays discrete roles in different pathogen response processes including basal resistance, enhanced resistance, effector-triggered immunity or in altered JA/ET-mediated immunity. Genome wide expression analysis reveals a role for PIE1 in the crosstalk between signalling processes and overall that SWR1c components might have distinct non-overlapping roles during gene regulation and expression.

Dr Kumar kindly provides a brief audio description of this paper:

 

Fournier-Level A, Perry EO, Wang JA, Braun PT, Migneault A, Cooper MD, Metcalf CJ, Schmitt J (2016) Predicting the evolutionary dynamics of seasonal adaptation to novel climates in Arabidopsis thaliana PNAS http://dx.doi.org/10.1073/pnas.1517456113 PNASpic

Mathematician Jessica Metcalf (Oxford) is an author on this US-led study that uses Arabidopsis to investigate the effect of climate change on evolution of fitness. Over four seasons plants were grown under four climatic conditions (present day, overall increased temp, winter-warming and poleward-migration temp) and 12 traits were measured as a proxy for fitness evolution. The data was used to simulate evolutionary trajectories over a 50-100 year period. The authors found that each climatic condition resulted in different outcomes where populations with fewer founding genotypes or less initial diversity adapted less well to altered conditions. This suggests that successful adaptation to climate change is linked to the diversity within a given population prior to the change occurring.

Zhang R, Calixto C, Marquez Y, Venhuizen P, Tzioutziou N, Guo W, Spensley M, Frey N, Hirt H, James A, Nimmo H, Barta A, Kalyna M, Brown J (2016) AtRTD2: A Reference Transcript Dataset for accurate quantification of alternative splicing and expression changes in Arabidopsis thaliana RNA-seq data. Preprint BioRxiv http://dx.doi.org/10.1101/051938 Open Access

This preprint includes researchers from the Universities of Dundee (John Brown), Glasgow (Hugh Nimmo) and Vienna and the James Hutton Institute and introduces AtRTD2, a new transcriptome for Arabidopsis and AtRTD2-QUASI for expression analysis and quantification of alternatively spliced isoforms in RNA-seq data.

Arabidopsis Research Roundup: May 5th

There are a bumper crop of papers in this edition of the Arabidopsis Research Roundup. First from the University of Manchester is a paper that identifies a protein involved in plant programmed cell death. Secondly are two papers from the University of Bristol that highlight the role of viruses in the reflectivity of plant leaves and an assessment of the growth parameters of Arabidopsis on different soil-types. Thirdly are three papers from University of Edinburgh that either use CRISPR-Cas technology to develop virus-research plants, investigate the relationship between photoperiod and metabolism or present a method for assessment of protein S-nitrosylation. Fourthly is a paper that includes a contribution from the University of Leeds that investigates the evolutionary and functional relationship of the WOX gene family. Finally is a study that highlights the role of the AUGMIN complex during microtubule activity that includes a contribution from the University of Leicester.

In addition, although not involving Arabidopsis, we should mention an exciting study from Gerben van Ooijen (Edinburgh) that has discovered a conserved circadian mechanism based on magnesium rhythms that is linked to energy expenditure.

Ge Y, Cai YM, Bonneau L, Rotari V, Danon A, McKenzie EA, McLellan H, Mach L, Gallois P (2016) Inhibition of cathepsin B by caspase-3 inhibitors blocks programmed cell death in Arabidopsis. Cell Death Differ. http://dx.doi.org/10.1038/cdd.2016.34 Open Access

The corresponding author of this paper is Patrick Gallois from the University of Manchester and includes contributions from Hazel McLellan in Dundee almongside Chinese and Austrian collaborators. This study investigates the role of caspase proteins on control of programmed cell death in plants. This research area has been hindered by the apparent lack of plant caspase orthologues despite pharmacological evidence that proteins with caspase activity are active in plants. The authors use a labeled caspase-3 inhibitor to identify the Arabidopsis Cathepsin B3 (AtCathB3) protein as having caspase activity, which was verified using recombinant proteins during in vitro enzyme assays. AtCathepsinB1,2,3 triple mutant plants demonstrate a reduction in PCD induced by different stresses and explains why caspase inhibitors are effective tools for studying PCD in plants. The core Cathepsin B protein is evolutionarily conserved suggesting that an ancestral pathway exists that controls PCD, the details of which require further study.

Maxwell DJ, Partridge JC, Roberts NW, Boonham N, Foster GD (2016) The Effects of Plant Virus Infection on Polarization Reflection from Leaves. PLoS One. 11(4):e0152836 http://dx.doi.org/ 10.1371/journal.pone.0152836 Open Access

Gary Foster’s research group at the University of Bristol collaborate with others at the University of York and in Australia for this study that investigates how plant viruses may modify gene expression to benefit their own transmission. They show that Potato virus Y and Cucumber mosaic virus (CMW), which both are transmitted by aphids, significantly reduce the amount of polarised light that is reflected from abaxial leaf surfaces of tobacco plants particularly when compared to the effects caused by non-insect vectored viruses. However this effect was not shown in Arabidopsis leaves infected by a variety of differently transmitted viruses. Interestingly ECERIFERUM6 (CER6) transcripts accumulate to higher levels following infection with insect vectored viruses and as this gene is involved in cuticle wax synthesis the authors suggest that induced changes in cuticle composition might be key in understanding how viruses encourage predation by their insect vectors. Finally the authors discuss the overall adaptive significance of these results.

Drake T, Keating M, Summers R, Yochikawa A, Pitman T, Dodd AN (2016) The Cultivation of Arabidopsis for Experimental Research Using Commercially Available Peat-Based and Peat-Free Growing Media. PLoS One. 11(4):e0153625 http://dx.doi.org/ 10.1371/journal.pone.0153625 Open AccessPeatPic

GARNet committee member Anthony Dodd, also from the University of Bristol, leads this study into the growth of Arabidopsis on peat-free media, which was motivated by the unsustainable use of peat-based composts. They found that biomass accumulation and seed yield were reduced on peat-free media and that some types of this media was more suspectible to fungal contamination. Overall vegetative phenotypic parameters were similar between plants grown on peat-based or peat-free media, indicating that this type of media will be appropriate for future analysis. However the seed yield was usually reduced, indicating that experiments looking at post-phase change phenotypes might not be as comparable between plants growth on media with different amount of peat.

Pyott DE, Sheehan E, Molnar A (2016) Engineering of CRISPR/Cas9-mediated potyvirus resistance in transgene-free Arabidopsis plants Mol Plant Pathol. http://dx.doi.org/10.1111/mpp.12417

Attila Molnar (Edinburgh) is the corresponding author on this study that uses the transformative technology CRISPR/Cas9 to engineer Arabidopsis plants that are resistant to potyvirus infection. This is achieved by targeting the genes encoding the translation initiation factor eIF(iso)4E that had been previously identified as being critical for viral establishment. Importantly they subsequently selected transgene-free plants that have no phenotypic changes when compared to wildtype growth under standard conditions. As the potyvirus Turnip Mosaic Virus is an important pathogen for vegetable crops this is potentially an extremely powerful technique for generating virus-resistance food crops.

Flis A, Sulpice R, Seaton DD, Ivakov AA, Liput M, Abel C, Millar AJ, Stitt M (2016) Photoperiod-dependent changes in the phase of core clock transcripts and global transcriptional outputs at dawn and dusk in Arabidopsis Plant Cell Environ. http://dx.doi.org/10.1111/pce.12754

This German–led study aims to connect the expression of photoperiod-length responsive circadian clock-regulated genes with those involved in metabolic processes such as starch degradation and includes a contribution from Professor Andrew Miller from the Edinburgh SynthSys Centre. The authors assess global gene expression by transcript profiling at photoperiods ranging from 4-18 hours and found that changes in transcript abundance at dawn throughout these photoperiods were as large as changes seen in individual experiments when comparing dawn and dusk. These complex interactions revealed coordinated regulation of key metabolic processes and begins to demonstrate how metabolism is linked to photoperiod.

Homem RA, Le Bihan T, Yu M, Loake GJ (2016) Identification of S-Nitrosothiols by the Sequential Cysteine Blocking Technique Methods Mol Biol. 1424:163-74. http://dx.doi.org/10.1007/978-1-4939-3600-7_14

This paper from the lab of Gary Loake (Edinburgh) describes the methods they use to investigate the role of protein S-nitrosylation in the immune responses of Arabidopsis. These are based on a modification of the biotin-switch technique, which they term sequential cysteine blocking.

Dolzblasz A, Nardmann J, Clerici E, Causier B, van der Graaff E, Chen J, Davies B, Werr W, Laux T (2016) Stem cell regulation by Arabidopsis WOX genes Mol Plant. S1674-2052(16)30029-6 http://dx.doi.org/10.1016/j.molp.2016.04.007

This German-led study includes work from the lab of Brendan Davies at the University of Leeds and investigates the role of the WUSCHEL-RELATED HOMEOBOX (WOX) transcription factor gene family during stem cell development and maintenance. Most members of the WUS-clade can largely substitute for WUSCHEL activity in the shoot meristem, which is absolutely dependent on a conserved WUS-box motif that is critical for the interaction with TOPLESS co-repressors. In contrast to the WUS clade, the WOX13 and WOX9 clades cannot substitute for WUS activity. The indicates that WOX control of shoot and floral meristem relies on certain currently not-fully-understood attributes of the WUS-clade of proteins.

Oh SA, Jeon J, Park HJ, Grini PE, Twell D, Park SK (2016) Analysis of gemini pollen 3 mutant suggests a broad function of AUGMIN in microtubule organization during sexual reproduction in Arabidopsis Plant J. http://dx.doi.org/10.1111/tpj.13192

David Twell (Leicester) is an author on his Korean-led study that reports on the identification of the new gem3 mutant, which displays defects in gametophytic development. Mutant plants exhibits disrupted cell division during male meiosis, at pollen mitosis I and throughout female gametogenesis. Gem3 is a hypomorphic allele of the AUGMIN subunit 6 gene, which is a component of Augmin complex responsible for microtubule (MT) nucleation in acentrosomal cells. In the gem3 mutant, the authors show that MT arrays are incorrectly distributed, likely causing the gametophyte-specific phenotypes and demonstrating a broad role for the augmin complex during sexual reproduction in flowering plants

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