Arabidopsis Research Roundup: January 11th

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 important structural relationship between xylan and cellulose. Thirdly members of Gos Micklem’s group in Cambridge are part of the Araport team that present their ThaleMine tool.

Richard Napier (University of Warwick) is a co-author on the fourth paper that introduces a new chemical tool for study of the auxin response. The penultimate paper includes Matthew Terry (University of Southampton) on a paper that investigates the role of a Fe-S-containing protein cluster in chlorophyll biosynthesis and finally there is a methods paper from Stefanie Rosa in Caroline Dean’s lab at the John Innes Centre that describes the use of FISH to detect single molecules of RNA.


Hayes S, Sharma A, Fraser DP, Trevisan M, Cragg-Barber CK, Tavridou E, Fankhauser C, Jenkins GI, Franklin KA (2016) UV-B Perceived by the UVR8 Photoreceptor Inhibits Plant Thermomorphogenesis. Current Biology http:/​/​dx.​doi.​org/10.1016/j.cub.2016.11.004

Open Access

This collaboration between the research groups of Kerry Franklin (University of Bristol) and Gareth Jenkins (University of Glasgow) looks at how the perception of UV-B light inhibits the morphological changes that occur in response to increased temperatures (thermomorphogenesis). This response includes induced hypocotyl elongation, which is mediated via PIF4 and various players in the auxin response. Interestingly the authors show that UV-B light perceived by UVR8 attenautes this response by preventing PIF4 abundance and by stabilising the the bHLH protein LONG HYPOCOTYL IN FAR RED (HFR1) protein. These results suggest that there exists a precise mechanism for fine-tuning the growth responses that occur in sunlight that would usually include both increased temperature and UV-B irradiation.
UVB_pic


Simmons TJ, Mortimer JC, Bernardinelli OD, Pöppler AC, Brown SP, deAzevedo ER, Dupree R, Dupree P (2016) Folding of xylan onto cellulose fibrils in plant cell walls revealed by solid-state NMR. Nat Commun.

http:/​/​dx.​doi.​org/10.1038/ncomms13902 Open Access
In this paper Paul Dupree (University Cambridge) collaborates both with colleagues in Spain and with his father Ray, who is a physicist at the University of Warwick. They use NMR to perform a structural analysis of xylan, which is the most prevalent non-cellulosic polysaccharide in the cell wall matrix and binds to cellulose microfibrils. Whereas in solution xylan forms a threefold helical screw, it flattens into a twofold helical screw ribbon to closely bind to cellulose when in the cell wall. They used the cellulose-deficient Arabidopsis irx3 mutant to show that the xylan two-fold screw confirmation breaks down when it cannot bind cellulose. The authors state that this finding has important implications in our understanding of the formation of the cell wall and perhaps more importantly how it might be broken down during attempts to maximise economic usages of plant biomass.

A local Cambridge newspaper reported that this finding could ‘pave the way for wooden skyscrapers’
XylanPic


Krishnakumar V, Contrino S, Cheng CY, Belyaeva I, Ferlanti ES, Miller JR, Vaughn MW, Micklem G, Town CD, Chan AP (2016) ThaleMine: A Warehouse for Arabidopsis Data Integration and Discovery. Plant Cell Physiol http:/​/​dx.​doi.​org/10.1093/pcp/pcw200 Open Access

This paper is presented by the Araport team, which is based in the USA but includes representatives from Gos Micklem’s lab in University of Cambridge. They outline the functionality of the ThaleMine data warehouse which is an important component of the tools included on Araport (https://www.araport.org/). ThaleMine collects a wide variety of data from public datasets and presents it in a easy-to-interrogate form, facilitating the experiments of both lab-based researchers or bioinformaticians. This tool is build upon the InterMine software framework, which has been widely adopted across other model organisms.

Chris Town and Sergio Contrino provided a hands-on workshop describing the tools on Araport in last year GARNet2016 meeting and their workshop materials can be downloaded here.


Steenackers WJ, Klíma P, Quareshy M, Cesarino I, Kumpf RP, Corneillie S, Araújo P, Viaene T, Goeminne G, Nowack MK, Ljung K, Friml J, Blakeslee JJ, Novák O, Zažímalová E, Napier RM, Boerjan WA, Vanholme B (2016) cis-cinnamic acid is a novel, natural auxin efflux inhibitor that promotes lateral root formation. Plant Physiol. http:/​/​dx.​doi.​org/pp.00943.2016 Open Access
cCApic
This pan-european collaboration includes members of Richard Napier’s lab at the University of Warwick. They outline the activity of a novel inhibitor of auxin efflux transport called cis-cinnamic acid (c-CA). When c-CA is applied to growth media plants appears to exhibit an auxin-response phenotype yet these experiments show that c-CA is neither an auxin or anti-auxin and in fact blocks local auxin efflux, thus causing buildup of cellular auxin. This effect does not occur with t-CA showing specificity for c-CA and it does not affect long distance auxin transport, which occurs through the phloem. Therefore this paper presents a new pharamolgical tool for the study of in planta auxin transport and homeostasis.


Hu X, Page MT, Sumida A, Tanaka A, Terry MJ, Tanaka R (2016) The iron-sulfur cluster biosynthesis protein SUFB is required for chlorophyll synthesis, but not phytochrome signaling. Plant J.

http:/​/​dx.​doi.​org/10.1111/tpj.13455

Matthew Terry and Mike Page (University of Southampton) are co-authors on this Japanese-led study that investigates the function of the SUFB subunit of the SUFBCD iron-sulfur cluster. These Fe-S protein clusters play roles in many metabolic processes and the SUFB mutant hmc1 exhibits a defect in chlorophyll biosynthesis due to an accumulation of Mg-containing biosynthetic intermediates. In addition both SUFC- and SUFD-deficient RNAi lines accumulated the same Mg intermediate indicating that the SUFBCD cluster is responsible for this step necessary for chlorophyll production.


Duncan S, Olsson TS, Hartley M, Dean C, Rosa S (2016) A method for detecting single mRNA molecules in Arabidopsis thaliana. Plant Methods. http:/​/​dx.​doi.​org/10.1186/s13007-016-0114-x

Open Access
This paper from is lead by Stefanie Rosa in Caroline Dean’s lab at the John Innes Centre describes a novel method for imaging single molecules of RNA by smFISH. They analyse the localisation of both nascent and mature mRNAs, allowing for analysis of the location of RNA processing and translation.<
RosaPic

Arabidopsis Research Roundup: January 22nd 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
Graphical Abstract
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: November 25th

This weeks Arabidopsis Research Roundup contains four papers each with a different focus. Firstly is a large-scale investigation that attempts to define the transcriptional changes that occur in response to bacterial infection. Second is a study that investigates a newly proposed role for the chloroplast chaperone Hsp93. Thirdly is another piece of work that also involves University of Oxford researchers and investigates the genetic networks that control leaf morphology. Finally is an updated plant-specific protocol for the commonly used technique of Chromatin Immunoprecipitation.

Lewis LA, Polanski K, de Torres-Zabala M, Jayaraman S, Bowden L, Moore J, Penfold CA, Jenkins DJ, Hill C, Baxter L, Kulasekaran S, Truman W, Littlejohn G, Prusinska J, Mead A, Steinbrenner J, Hickman R, Rand D, Wild DL, Ott S, Buchanan-Wollaston V, Smirnoff N, Beynon J, Denby K, Grant M (2015) Transcriptional Dynamics Driving MAMP-Triggered Immunity and Pathogen Effector-Mediated Immunosuppression in Arabidopsis Leaves Following Infection with Pseudomonas syringae pv tomato DC3000 Plant Cell. http://dx.doi.org/10.1105/tpc.15.00471 Open Access

This ‘Large Scale Biology’ publication is a collaboration between the Universities of Exeter and Warwick, led by Murray Grant and current GARNet Advisory board member Katherine Denby. This study investigates the transcriptional changes that occur over a long time course in response to infection by the pathogen Pseudomonas syringae pv tomato DC3000. The authors aim to differentiate between the changes associated with endogenous microbial-associated molecular pattern (MAMP)-triggered immunity (MTI) and those orchestrated by pathogen effectors. The responses to pathogenic and non-pathogenic P.syringae were compared and using novel computational analysis, it was shown that the majority of gene expression changes that contribute to disease or defense responses occurred within 6hour post-infection, well before pathogen multiplication. Broadly it was found that chloroplast-associated genes are suppressed by a MAMP-triggered response, presumably to restrict nutrient availability. Ultimately this manuscript identified specific promotor elements that are involved in either the MTI response or utilised by the infecting bacteria.

Corresponding author Professor Murray Grant kindly takes ten minutes to discuss the finding of this paper and the community resource that it represents. He also discusses another paper involving the Jasmonate response that resulted from this dataset and was recently highlighted in the Research Roundup. Interview end at 11m10s.

Flores-Pérez Ú1, Bédard J1, Tanabe N2, Lymperopoulos P2, Clarke AK3, Jarvis P (2015) Functional analysis of the Hsp93/ClpC chaperone at the chloroplast envelope Plant Physiology. http://dx.doi.org/10.1104/pp.15.01538 Open Access

Paul Jarvis (Oxford) is the corresponding author on this study in which his lab collaborates with Swedish researchers to investigate the role of the Hsp93/ClpC chaperone protein in protein import into the chloroplast. This recently postulated role for this protein has not yet been experimental tested so they generated a hsp93[P-] mutant that lacked a functional ClpP-binding motif (PBM), which confers the already determined role for Hsp93 in proteolysis that occurs in the chloroplast stroma. The hsp93[P-] mutant localises to the chloroplast envelope and associates with TIC transport machinery but was unable to complement the phenotypes of a hsp93 null mutant. This showed that the PBM domain was essential for its function. Expression of the Hsp93[P-] mutant in the hsp93 null background did not improve protein import so the authors concluded that these results do not confirm this newly postulated role for the protein and they suggest that its functional role occurs immediately after its substrate had been transported into the chloroplast.

Rast-Somssich MI, Broholm S, Jenkins H, Canales C, Vlad D, Kwantes M, Bilsborough G, Dello Ioio R, Ewing RM, Laufs P, Huijser P, Ohno C, Heisler MG, Hay A, Tsiantis M (2015) Alternate wiring of a KNOXI genetic network underlies differences in leaf development of A. thaliana and C. hirsuta Genes Dev. 29(22):2391-404 http://dx.doi.org/10.1101/gad.269050.115 Open Access

The study includes researchers from Oxford and Southampton Universities in collaboration with those from Italy, France and Germany in work that is led by Angela Hay and Miltos Tsiantis, who were both previously based in Oxford. This is familiar territory for this group as they compare leaf development between Arabidopsis, which has simple leaves, and the related , Cardamine hirsuta, which has dissected leaves. In this new work they transfer the SHOOTMERISTEMLESS (STM) and BREVIPEDICELLUS (BP) homeobox genes between the two species and investigate their ability to modify leaf form. In Cardamine, expression of BP is controlled by crosstalk between the microRNA164A (MIR164A)/ChCUP-SHAPED COTYLEDON (ChCUC) module and ChASYMMETRIC LEAVES1 (ChAS1) gene. However this regulatory network does not function in Arabidopsis and therefore leads to the establishment of differing regulatory networks that the authors propose are responsible for the alterations in organ geometry.

Posé D, Yant L (2016) DNA-Binding Factor Target Identification by Chromatin Immunoprecipitation (ChIP) in Plants Methods Mol Biol. 1363:25-35. http://dx.doi.org/10.1007/978-1-4939-3115-6_3

Levi Yant is a new member of faculty at the John Innes Centre and is the lead author on this paper that introduces an updated protocol for Chromatin Immunoprecipitation in Plants (ChIP). They have used this technique in his lab to identify target genes for a number of transcriptional regulators that are involved in Arabidopsis floral development.

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