Guest Post from Sam Downs, 2nd Year Undergraduate at Cambridge University.
This April, the Sainsbury Laboratory at Cambridge university (SLCU) held its first large meeting – SLS ’16 – on Induced Plant Development. The keynote speakers were Prof. Sofie Goormachtig on root strigolactone signalling to Prof. Christian Fankhauser on growth changes in response to light, with others addressing topics ranging from large scale morphological studies to cell and molecular biology.
It was a first for me too; like most undergraduates, I hadn’t yet attended an academic conference. As I imagine many find at their first conference, it was slightly intimidating to be in a room half-full of PIs – the rest being PhD students, with their own research projects underway, wasn’t much better. There was nothing for it but to get stuck in though, and talking to people about their talks and posters proved easier than I had thought. It’s a testament to the friendliness of the plant science community that everyone was willing to explain their work from the bottom up to a passing undergrad!
As an outsider to research, it was interesting to note what people felt was important to communicate in talks and posters. They seemed to be broadly results-driven or process-driven, and I found this was especially marked in the posters; many were reporting new techniques, such as growing Arabidopsis roots on microfluidics chips, or laser imaging of cell movements, whilst others (such as Dr Dana MacGregor’s prize-winning poster on seed dormancy) drew their main interest from the phenomenon they showed. This is quite different to the way that I’ve mainly engaged with science – essentially, as an interested member of the public. This year I’ve been helping to run the Cambridge student biological society, and we’ve hosted a number of talks by UK scientists. Their talks are mainly of the former kind; essentially reporting new results, suitable for a lay audience. It was thus quite new to me to hear technique-driven presentations, and exciting too – a look above the parapet of summer exam revision (driven, of course, by an entirely different sort of result!).
What struck me most of all, though, was the hearing the questions people asked at the end of each talk. Through these, I got a stronger sense of how active researchers think about science than even the talks or the posters could. As an undergraduate, I’m used to hearing researchers talk about results, and sometimes about methods too; but the biggest difference was how the audience parsed what they heard. The questions focused on the experimental process and the physiology of the whole plant (“What happens to Rorippa aquatica if it’s in warm water, [when heat and submersion have opposite effects]?” “Is the plant’s response to UV-B modulated in the diurnal cycle?”). This is a different way of thinking (perhaps regrettably) to that taken at undergraduate level; we tend to focus more on isolated details, so the bigger picture of how a result came about in the lab and in the organism can be missed. It was a reminder to me of the challenge of getting across this gap from obsession with facts to obsession with science.
Overall, I learnt a lot in the short duration of the SLS, both about what’s going on in plant development and about life in science. I would life to thank the organisers, the speakers, and especially Geraint Parry from GARNet who offered me the opportunity to attend it.
Temperature mediated developmental changes in Rorippa aquatica
This weeks Arabidopsis Research Roundup contains an eclectic mix of investigations. Firstly is a study from Peter Unwin that investigates the molecular factors that control interactions between plants and nematode parasites. Secondly is a study led by John Christie that investigates the factors that control hypocotyl curvature. Thirdly is a fascinating proof-of-concept synbio-style study from Rothamstead Research where an algal gene is transferred into Arabidopsis in the hope of developing a phytomediation-based solution to heavy metal contamination. Fourthly is a study from David Bass that catalogues protist species that feed on leaf-microorganisms whilst finally John Carr heads a study that compares RNA-dependent RNA polymerases from Arabidopsis and Potato.
Eves-van den Akker S, Lilley CJ, Yusup HB, Jones JT, Urwin PE (2016) Functional C-terminally encoded plant peptide (CEP) hormone domains evolved de novo in the plant parasite Rotylenchulus reniformis. Mol Plant Pathol. http://dx.doi.org/10.1111/mpp.12402).
This study is a collaboration between researchers at the Universities of Dundee and Leeds, led by Peter Unwin. The focus of the paper is the interaction of Plant-Parasitic Nematodes (PPNs) with their plant hosts. PPNs stimulate redifferentiation of vascular tissues to form ‘feeding structures’ that benefit the parasite. This process is mediated by a diverse family of effector proteins termed C-terminally Encoded Peptide plant hormone mimics (CEPs). This study investigates the CEPs from the nematode Rotylenchulus reniformis and suggests that these peptides evolved de novo in this organism. They show that the activity of a synthetic peptide corresponding to RrCEPs causes a reduction in primary root elongation whilst upregulating a set of genes including the nitrate transporter AtNRT2.1. The authors propose that CEPs evolved in R. reniformis to allow sustained biotrophy by upregulating a specific set of feeding-responsive genes and by limiting the size of the feeding site produced. This study represents an exciting introduction to a currently under-researched area within plant-pathogen interactions.
Sullivan S, Hart JE, Rasch P, Walker CH, Christie JM (2016) Phytochrome A Mediates Blue-Light Enhancement of Second-Positive Phototropism in Arabidopsis. Front Plant Sci. 7:290 http://dx.doi.org/10.3389/fpls.2016.00290Open Access
John Christie (Glasgow) is the corresponding author on this investigation into the role of the blue-light receptor phototropin 1 (phot1) during hypocotyl phototropism. Curvature of this organ is enhanced by treatment by red-light mediated by the phytochromeA receptor. However this study shows that pre-treatment with blue-light can also enhance this hypocotyl curvature although this did not occur at higher light intensities. In addition phototropic enhancement was also lacking when PHOT1 is expressed only in the hypocotyl epidermis. Therefore the study shows that the phyA impact on phot1 signaling is restricted to low light intensities and in tissues other than the epidermis.
Zhong Tang, Yanling Lv, Fei Chen, Wenwen Zhang, Barry P. Rosen, and Fang-Jie Zhao (2016) Arsenic Methylation in Arabidopsis thaliana Expressing an Algal Arsenite Methyltransferase Gene Increases Arsenic Phytotoxicity J. Agric. Food Chem. http://dx.doi.org/10.1021/acs.jafc.6b00462Open Access
This synthetic biology-focused study is led by Fang-Jie Zhao at Rothamstead Research. The authors take an algal gene (arsM) that allows the transformation of inorganic arsenic to a more volatile methylated version. The biological activity of this enzyme was successfully transferred to two different Arabidopsis ecotypes. However interestingly these transgenic plants became more sensitive to arsenic in growth media suggesting that the new methylated arsenic intermediate is more phytotoxic than inorganic arsenic. Therefore this study demonstrates a negative consequence of this project that attempted to engineer arsenic tolerance in plants. Once again this demonstrates that nature rarely acts predictably and any great ideas usually need to be tested in vivo.
Ploch S, Rose L, Bass D, Bonkowski M (2016) High Diversity Revealed in Leaf Associated Protists (Rhizaria: Cercozoa) of Brassicaceae J Eukaryot Microbiol. http://dx.doi.org/10.1111/jeu.12314
After a fantastic opening line in the abstract, ‘The largest biological surface on earth is formed by plant leaves’, this study includes the work of David Bass from the Natural History Museum in London. They investigate the abundance of protists that associate with leaf-inhabiting microorganisms, the “phyllosphere microbiome“. Their findings demonstrate that protists should be considered an important part of the diversity of plant-interacting microbial organisms.
Hunter LJ, Brockington SF, Murphy AM, Pate AE, Gruden K, MacFarlane SA, Palukaitis P, Carr JP (2016) RNA-dependent RNA polymerase 1 in potato (Solanum tuberosum) and its relationship to other plant RNA-dependent RNA polymerases Sci Rep. 6:23082 http://dx.doi.org/10.1038/srep23082Open Access
John Carr (Cambridge) is the UK-lead on this collaboration with Slovenian and Korean researchers. They primarily investigate the role of the RDR1 RNA-dependent RNA polymerase (RDRs) in potato. In Arabidopsis the RDR1 gene contributes to basal viral resistance but potato plants deficient in StRDR1 do not show altered susceptibility to three different plant viruses. In addition they perform a phylogenetic analysis on the RDR genes and identify a novel RDR7 gene that is only found in Rosids (but not Arabidopsis.
This weeks Arabidopsis Research Roundup includes three papers from the Norwich Research Park on very different topics. Firstly the team of Richard Morris investigates the nature of mRNA sequences that are transported over long-distances. Secondly Kristen Bomblies introduces a set of genes involved in the evolution of weediness whilst finally Cyril Zipfel is involved in research that developed a novel assay for identification of defence signaling components. Elsewhere Paul Devlin’s group from RHUL characterises the interactions between components of a light signaling pathway whilst Alex Webb and co-workers use a novel assay to confirm the activity of plant nucleotide cyclases involved in calcium signaling.
Richard Morris (JIC) is the lead author on this ‘Breakthrough Report’ that analyses previously generated data in order to ascertain whether populations of mRNAs that are transported long-distances in the phloem are selected by any mechanism. They showed that in general mobile transcripts can be explained by their abundance and half-life, leading to the conclusion that the majority of transported mRNAs are not selected on the basis of their primary sequence.
Baduel P, Arnold B, Weisman CM, Hunter B, Bomblies K (2016) HABITAT-ASSOCIATED LIFE HISTORY AND STRESS-TOLERANCE VARIATION IN ARABIDOPSIS ARENOSA Plant Physiol. http://dx.doi.org/10.1104/pp.15.01875Open Access
Recent ECR Research Grant awardee Kristen Bomblies (JIC) leads this investigation into growth variation in Arabidopsis Arenosa. This obligate outbreeding relative of A.thaliana is normally not weedy but can transition to weediness in conditions of high disturbance. This study uses transcriptome sequencing, genome resequencing scans for selection, and stress tolerance assays to investigate a weedy population of A.arenosa that has been discovered growing along railway lines through central and Northern Europe. These plants show constitutive upregulation of genes involved in heat shock and freezing tolerance. Amongst the genes that were strongly selected in the weedy population was LATE ELONGATED HYPOCOTYL (LHY), which is known to regulate many stress-regulated genes in A.thaliana and therefore might be a significant determinant in the evolution of weediness.
Saur IM, Kadota Y, Sklenar J, Holton NJ, Smakowska E, Belkhadir Y, Zipfel C, Rathjen JP (2016) NbCSPR underlies age-dependent immune responses to bacterial cold shock protein in Nicotiana benthamiana Proc Natl Acad Sci U S A. http://dx.doi.org/10.1073/pnas.15118471
This Australian-Austrian-UK collaboration includes work from the lab of Cyril Zipfel (TSL). The initial work in this study uses the Nicotiana benthamiana expression system to identify novel leucine-rich repeat (LRR)-containing pattern recognition receptors (PRR) that interact with the BRI1-ASSOCIATED KINASE1 (BAK1) protein, which is important in recognition of bacterial pathogens. N.benthamiana plants were treated with the effector peptide csp22 and the resulting samples were immunopurified with BAK1. They identified a protein termed RECEPTOR-LIKE PROTEIN REQUIRED FOR CSP22 RESPONSIVENESS (NbCSPR) which, when silenced in tobacco resulted in reduced defence responses to the csp22 peptide. Subsequent expression of NbCSPR in Arabidopsis caused antibacterial resistance. Primarily the authors demonstrate a novel protocol that could be used to identify further novel components in signaling pathways that response to pathogen attack.
Siddiqui H, Khan S, Rhodes BM, Devlin PF (2016) FHY3 and FAR1 Act Downstream of Light Stable Phytochromes Front Plant Sci. 7:175 http://dx.doi.org/10.3389/fpls.2016.00175Open Access Paul Devlin (RHUL) is the lead on this study that looks at the regulation of the ELF4 gene. This gene is a light-dependent target for the transcription factors FHY3 and FAR1 and the authors demonstrate that this signaling acts via not only the phytochrome PhyA but also through phyB, phyD, and phyE. ELF4 induction by FHY3 and FAR1 occurs specifically in the evening, which allows expression of ELF4 beyond dusk during shortening days. Without the action of the two transcription factors, this ELF4 expression is not maintained resulting in further downstream gene expression changes that alters the cycling of the circadian clock.
Abdul-Awal SM, Hotta CT, Dodd AN, Davey MP, Smith AG, Webb AA (2016) NO-mediated [Ca2+]cyt increases depend on ADP-ribosyl cyclase activity in Arabidopsis Plant Physiol. http://dx.doi.org/10.1104/pp.15.01965Open Access
This study continues Alex Webb’s (Cambridge) work in the area of calcium signaling by investigating the control of cyclic ADP-ribose (cADPR) production in Arabidopsis. Although the role of cADPR in plant signaling is well established there are no ADPR cyclase enzymes with strong similarity to known metazoan enzymes in previously interrogated plant genomes. This argues for either a unique synthesis route for cADPR or for the activity of an enzyme with low sequence similarity to previously characterized cyclases. To test these difference ideas the authors developed two novel fluorescence-based assays to measure ADPR cyclase activity. These assays reveal that indeed there is activity that resembles the characteristics of a cyclase, which additionally is activated by nitric oxide (NO). This potentially links NO signaling activity to increased levels of cADPR and mobilisation of a calcium signal.
This weeks Arabidopsis Research Roundup features papers that build upon the history of research in each featured lab. Firstly Gareth Jenkins from Glasgow continues to investigate mechanisms of UV-B signaling whilst Laila Moubayidin, now at the JIC, is involved in work that investigates the multiple factors that control root meristem size. Finally we present a three protocol papers that are featured in a new colelction of articles that focus on protocols that can be used to assess different environmental responses.
Findlay KM, Jenkins GI (2016) Regulation of UVR8 photoreceptor dimer/monomer photo-equilibrium in Arabidopsis plants grown under photoperiodic conditions. Plant Cell Environment http://dx.doi.org/10.1111/pce.12724Open Access
The research group led by Gareth Jenkins (Glasgow) continues their work on the plant response to UV in this study that investigates the binding patterns of the UVR8 protein. UVR8 mediates the plant response to UV-B light and the protein either exists in a monomeric (active) or dimeric (inactive) form. This study shows that UVR8 maintains dimer/monomer photo-equilibrium through diurnal photoperiods and that the REPRESSOR OF UV-B PHOTOMORPHOGENESIS 1 (RUP1) and RUP2 proteins are necessary for maintaining this equilibrium. Interestingly they show that the UVR8 balance is tipped toward the monomeric form in lower temperatures. This shows that the protein does not act as a simple switch to signal for changes in UV-B as its effect is influenced by environmental parameters outside of the light source.
Moubayidin L, Salvi E, Giustini L, Terpstra I, Heidstra R, Costantino P, Sabatini S (2016) A SCARECROW-based regulatory circuit controls Arabidopsis thaliana meristem size from the root endodermis Planta http://dx.doi.org/10.1007/s00425-016-2471-0Open Access
Laila Moubayidin now works as a postdoc with Lars Ostergaard at the JIC but this work is the result of research conducted with Sabrina Sabatini in Rome. In this study they continue the labs investigation into the role of the SCARECROW (SCR) protein in the control of root meristem size. They show that SCR, from endodermal cells, sustains a gibberellic acid signal by regulating RGA REPRESSOR OF ga1-3 (RGA) protein stability. This in turn controls the activity of the cytokinin responsive transcription factor ARR1 at the root transition zone. This activity therefore maintains a balance of cell division and differentiation that maintains correct meristem size.
A new edition of ‘Methods in Molecular Biology’ focuses on ‘Environmental Responses in Plants’ and includes a number of papers featuring UK authors who work on Arabidopsis.
This weeks Arabidopsis Research Roundup features a paper from David Baulcombe and Joe Ecker that further deciphers mechanisms of RNA silencing and is kindly discussed by postdoc Mat Lewsey in a short audio description. Elsewhere there are three studies that include researchers from CPIB in Nottingham. Leah Band contributes to a study that links environment sensing, cell death and auxin signaling whilst Ive De Smet leads a study that finds new proteins involved in cell division. Malcolm Bennett and John King take a modeling approach to describe auxin signaling via the GH3 protein family. Finally Frank Menke leads a study that provides more detail into Pattern Recognition Receptor (PRR) mediated immune signaling and then Jim Dunwell participates in a paper that describes a new method of analyzing GWAS data.
Lewsey MG, Hardcastle TJ, Melnyk CW, Molnar A, Valli A, Urich MA, Nery JR, Baulcombe DC, Ecker JR (2016) Mobile small RNAs regulate genome-wide DNA methylation. Proc Natl Acad Sci U S A. http://dx.doi.org/10.1073/pnas.1515072113Open Access
Over the past few years RNA-mediated silencing has emerged a key mechanism for the control of gene expression. This study is a collaboration between the lab of Sir David Balcombe (Cambridge) and Joe Ecker at the SALK institute in California. Mat Lewsey, who is a British postdoc working with Professor Ecker, kindly provided a short audio description of the paper.
These groups have previously shown that sRNAs are highly mobile throughout the plant. This study shows that thousands of loci expressed in roots are dependent on mobile sRNAs generated from the shoot. They unpick the genetic basis of this response showing that it is largely dependent on the DOMAINS REARRANGED METHYLTRANSFERASES 1/2 (DRM1/DRM2) but not CHROMOMETHYLASE (CMT)2/3 DNA methyltransferases. They also show that mobile sRNAs are resposible for the silencing of TEs that are found in gene-rich regions, although this is not a physiologically important response in Arabidopsis, which contains a relatively small amount of transposon tissue. Interestingly they a show that sRNAs generated from different Arabidopsis ecotypes are able to move across graft junctions and can cause methylation in usually unmethylated regions.
Xuan W, Band LR, Kumpf RP, Van Damme D, Parizot B, De Rop G, Opdenacker D, Möller BK, Skorzinski N, Njo MF, De Rybel B, Audenaert D, Nowack MK, Vanneste S, Beeckman T (2016) Cyclic programmed cell death stimulates hormone signaling and root development in Arabidopsis. Science . 351(6271):384-7 http://dx.doi.org/10.1126/science.aad2776
This study is led by Tom Beeckman from Gent University and features Leah Band from CPIB in Nottingham. They reveal an exciting relationship between cell death in root cap cells and hormone signaling. The root cap is a protective tissue that overlies the Arabidopsis root tip and might be considered as an ‘inactive’ tissue. However this study shows that an auxin signal released from root cap cells sets the spacing of lateral organs along the root. As root cap cells move up the root they undergo programmed cell death, which in turn releases a pulse of auxin and establishes a pattern of lateral root formation. The authors suggest that this relationship might integrate external soil conditions so that lateral roots will develop to optimise uptake of water and nutrients. It is well known that an auxin signal simulates lateral root formation but this study provides an explanation as to the genesis of this signal and its integration with external environmental factors.
Yue K, Sandal P, Williams EL, Murphy E, Stes E, Nikonorova N, Ramakrishna P, Czyzewicz N, Montero-Morales L, Kumpf R, Lin Z, van de Cotte B, Iqbal M, Van Bel M, Van De Slijke E, Meyer MR, Gadeyne A, Zipfel C, De Jaeger G, Van Montagu M, Van Damme D, Gevaert K, Rao AG, Beeckman T, De Smet I (2016) PP2A-3 interacts with ACR4 and regulates formative cell division in the Arabidopsis root. Proc Natl Acad Sci U S A. http://dx.doi.org/10.1073/pnas.1525122113
This broad collaboration between US-UK and Belgian researchers is led by Tom Beeckman and Ive De Smet, who works at CPIB in Nottingham. In addition it includes a contribution from Cyril Zipfel at TSL. This study aimed to identify proteins that interact with the plasma membrane-localized receptor kinase ARABIDOPSIS CRINKLY 4 (ACR4), which plays a role in the control of cell division in the Arabidopsis root. They find that PROTEIN PHOSPHATASE 2A-3 (PP2A-3), a catalytic subunit of PP2A holoenzymes interacts with ACR4 and has a previous uncharacterised role in control of formative cell divisions. The authors show that the biochemical network that links ACR4 and PP2A-3 is regulated by phosphorylation.
This paper led by Professor Malcolm Bennett and John King from CPIB is an example of the growing number of multi-disciplinary interactions between biologists and mathematicians. Here a model is developed that interrogates auxin signaling and homeostasis through the GH3 gene family. This includes a parameter that considers auxin transport via the LAX3 influx protein, which, together with the activity of GH3 proteins can facilitate a positive feedback loop that allows cells to response to excess auxin.
Mithoe SC, Ludwig C, Pel MJ, Cucinotta M, Casartelli A, Mbengue M, Sklenar J, Derbyshire P, Robatzek S, Pieterse CM, Aebersold R, Menke FL (2016) Attenuation of pattern recognition receptor signaling is mediated by a MAP kinase kinase kinase. EMBO Rep. http://dx.doi.org/10.15252/embr.201540806Open Access
Frank Menke (TSL, Norwich) is the leader on this collaboration between UK, Dutch and Swiss researchers that investigates innate immunity signaling mediated via Pattern Recognition Receptors (PRRs). Tight control of this signalling is very important to prevent spurious activation of the immune response. These authors find that the differentially phosphorylated MKKK7 can interact with the FLS2 protein, which is key in the perception of bacterial flagellin. In turn MKKK7 attenuates the signalling of a downstream MAPK that contributes to defence-related gene expression. Therefore the show that the FLS2-MKKK7 signaling module is critical for control of innate immunity.
Wang SB, Feng JY, Ren WL, Huang B, Zhou L, Wen YJ, Zhang J, Dunwell JM, Xu S, Zhang YM (2016) Improving power and accuracy of genome-wide association studies via a multi-locus mixed linear model methodology. Sci Rep. http://dx.doi.org/10.1038/srep19444Open Access
Professor Jim Dunwell (Reading) is a UK contributor to this largely Chinese publication that introduces a new method to analysis GWAS-style data. They propose an analysis based on random-SNP-effect MLM (RMLM) and a multi-locus RMLM (MRMLM) and using stimulations show that their new method can be powerful than conventional types of analysis. To test the method they analysed flowering time traits in Arabidopsis and detected more genes that were involved in the process.
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/ncomms10269Open 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.2015.01078Open 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.
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.
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.1005660Open 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.2015.10.007Open 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.
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.
This December 9th Arabidopsis Research Roundup includes four rather different studies. Firstly we include an excellent audio description from David Salt about a new type of GWAS analysis that his lab was involved in developing. This allowed identification of new genetic loci involved in molybdenum signalling. Secondly Isabelle Carre’s group from Warwick presents a study into the interactions that define the functioning of the circadian clock. Thirdly Mike Blatt leads a study that models stomatal opening and finally we include an investigation of the DOG1 gene, that includes a contribution from Fuquan Liu.
Forsberg SK, Andreatta ME, Huang XY, Danku J, Salt DE, Carlborg Ö (2015) The Multi-allelic Genetic Architecture of a Variance-Heterogeneity Locus for Molybdenum Concentration in Leaves Acts as a Source of Unexplained Additive Genetic Variance PLoS Genet. e1005648. http://dx.doi.org/10.1371/journal.pgen.1005648Open Access.
Current GARNet Chairman David Salt (Aberdeen) is the UK lead on this collaboration with the lab of Orjan Carlborg from Uppsala in Sweden. The novelty of this paper is in the development of a new technique to measure Genome-Wide Association using the variance in SNP differences instead of using the mean. Professor Salt explained this vGWA technique in the attached audio-file, which is especially useful for people not so familiar with GWAS. Using this vGWA technique the authors were able to re-analyse an old dataset to gain additional understanding of how certain genetic loci are regulated to explain differences in the production of the essential nutrient molybdenum. Overall this paper introduces an analysis technique that can hopefully be used by other members of the community to analyse/re-analyse their data with increased rigour.
This is the 10minute audio file where David explains the paper:
Adams S, Manfield I, Stockley P, Carré IA (2015) Revised Morning Loops of the Arabidopsis Circadian Clock Based on Analyses of Direct Regulatory Interactions. PLoS One.10(12):e0143943. http://dx.doi.org/ 10.1371/journal.pone.0143943Open Access
This collaboration between the Universities of Warwick and Leeds is led by Isabelle Carré and investigates the Arabidopsis circadian clock. They analysed the in vivo interactions of the LATE ELONGATED HYPOCOTYL (LHY) protein with promotors of other clock components. This uncovered a novel regulatory loop between LHY and the CIRCADIAN CLOCK ASSOCIATED-1 (CCA1) gene. Furthermore they show LHY acts as a repressor of all other clock components, clearly placing this protein as a key regulatory component of the Arabidopsis clock.
Minguet-Parramona C, Wang Y, Hills A, Vialet-Chabrand S, Griffiths H, Rogers S, Lawson T, Lew V, Blatt MR (2015) An optimal frequency in Ca2+ oscillations for stomatal closure is an emergent property of ion transport in guard cells. Plant Physiol. http://dx.doi.org/10.1104/pp.15.01607Open Access
Mike Blatt is the corresponding author for this collaboration between Glasgow, Cambridge and Essex Universities. There are a good number of UK researchers who investigate the factors that regulate stomatal opening and this study looks at the role of calcium oscillations in this process. They have used the Arabidopsis OnGuard model that faithfully reproduces the optimum 10minute period of Ca2+ oscillation in guard cells. They used experimentally derived kinetics to describe the activity of ion transporters in the plasma membrane and tonoplast. Overall they discovered that the calcium oscillations are actually a by-product of the ion transport that determines stomatal aperature and not the overall controlling factor.
Cyrek M, Fedak H, Ciesielski A, Guo Y, Śliwa A, Brzeźniak L, Krzyczmonik K, Pietras Z, Liu F, Kaczanowski S, Swiezewski S (2015) Seed dormancy in Arabidopsis thaliana is controlled by alternative polyadenylation of DOG1 Plant Physiol. http://dx.doi.org/10.1104/pp.15.01483
Fuquan Liu (Queens, Belfast) is the UK contributor to this Polish-led study focused on the DOG1 gene, which is a key regulator of Arabidopsis seed dormancy. Previously it had been shown that the C-terminus of DOG1 is not conserved in many other plant species. The DOG1 transcript is alternatively polyadenylated and the authors show that Arabidopsis mutants that lack current 3’ RNA processing also show defects in seed dormancy. The shorter version of DOG1 is able to rescue the dog1 phenotype, which allows the authors to propose that DOG1 is a key regulator of seed dormancy and that the phenotypes of RNA processing mutants are linked to the incorrect processing of this specific mRNA species.
A recent Arabidopsis Research Roundup included a paper from Adrienne Roeder’s lab in Cornell that includes James Locke and Henrik Jonsson from SLCU. The research focuses on the Arabidopsis sepal, which has been the central theme of the Roeder lab since it was set up a few years ago. On a personal level I recall[…]
This weeks Arabidopsis Research Roundup begins with two papers that look at endogenous and exogenous causes of cell proliferation. Firstly Mike Bevan (JIC) leads a team that looks into the role of controlled protein degradation in this process whilst secondly, Peter Etchells from Durham is a co-author on a study that investigates how nematode pathogens[…]
This weeks Arabidopsis Roundup again includes a broad selection of research topics. Firstly researchers at SLCU are involved in work that describes Arabidopsis sepal development. Secondly Cyril Zipfel from TSL leads a study that adds a layer of complexity to our knowledge of cellular pathogen perception. Thirdly the group of Reiner van der Hoorn from[…]
Often times in the scientific literature you will find that a topic suddenly becomes trendy. This might follow a technological advancement that opens up a new subject area, a serendipitous co-discovery or after an important publication opens a Pandoras box of questions. Over the past few months the Arabidopsis research literature has seen a number[…]
Todays Arabidopsis Research Roundup includes some excellent examples of UK labs engaged in collaborative work with researchers from around the globe. However first up is a study solely from the John Innes Centre, led by Vinod Kumar, that investigates the role of PIF4 during the thermosensory response. Secondly David Evans (Oxford Brookes University) is a[…]
The first Arabidopsis Research Roundup of 2017 includes a wide range of studies that use our favourite model organism. Firstly Kerry Franklin (University of Bristol) is the corresponding author on a paper that describes the complex interaction between the responses to sunlight and heat. Secondly Paul Dupree (University of Cambridge) leads a study that defines[…]
The final Research Roundup of 2016 includes two papers that take different strategies toward the ultimate aim of crop improvement and use Arabidopsis as a tool for their initial discoveries. Firstly Christine Raines (University of Essex) uses a transgenic approach to upregulate enzymes of the calvin cycle while researchers from Rothamstead and Oxford use a[…]
This weeks Arabidopsis Research Roundup includes three papers across a wide range of topics. Firstly is a widely-reported study, described here with an audio description by Nik Cunniffe and Sanjie Ziang, of the evolutionary relationship between viral infection, pollinator attraction, plant fertility and miRNA-regulated gene expression. Secondly, Gordon Simpson is a co-author on a paper[…]
This weeks Arabidopsis Research Roundup includes broad representation from Norwich Research Park with Caroline Dean, Enrico Coen and Cyril Zipfel each leading studies that focus respectively on the regulation of transcriptional state, auxin patterning that defines leaf shape or the molecular basis of the PAMP response. Elsewhere Liam Dolan (Oxford) leads, and Malcolm Bennett (CPIB)[…]
Almost a thousand researchers attended this year’s international Conference on Arabidopsis research (ICAR) in South Korea. ICAR2016 was my first experience of a large plant science conference, although it wasn’t a completely foreign experience as I recognised a few faces from the 2015 UK PlantSci conference. I was among the hundreds of delegates presenting a[…]