This edition of the GARNet research roundup includes six papers that look at different areas of plant biology. Firstly is a Belgian-led study with co-authors from Nottingham that introduces adaptive Xerobranching, a cereal-root response that can be mimicked in Arabidopsis by modulating ABA signaling. Second is study from Juriaan Ton’s lab in Sheffield that investigates the extent of DNA methylation during transgenerational acquired disease resistance. Third is paper from the John Innes Centre that places the DET1/COP1-PIF4 signaling module as a key determinant of the plants decision to allocate resources toward growth or defence.
The fourth paper is from Siobhan Braybrook’s (now ex-) lab at SLCU and provides an extensive dataset of the shape of leaf pavement cells across plant lineages. The penultimate paper is from a group at the University of Birmingham investigating the role of TOPII in the removal of damaging chromosome interlocks that occur during meiosis. The final paper returns to the ABA signalling with a study from Rothamsted Research that looks at the impact of the N-end rule on the different growth responses that occur during seed germination.
Orman-Ligeza B, Morris EC, Parizot B, Lavigne T, Babé A, Ligeza A, Klein S, Sturrock C, Xuan W, Novák O, Ljung K, Fernandez MA, Rodriguez PL, Dodd IC, De Smet I, Chaumont F, Batoko H, Périlleux C, Lynch JP, Bennett MJ, Beeckman T, Draye X (2018) The Xerobranching Response Represses Lateral Root Formation When Roots Are Not in Contact with Water. Current Biology. doi: 10.1016/j.cub.2018.07.074
Emily Morris and Beata Orman-Ligeza are co-authors on this Belgian-led study that includes authors from the Universities of Nottingham and Lancaster. They introduce a new adaptive response termed xerobranching that defines the repression of root branching when a root tip is not in contact with wet soil. This response occurs in cereal roots but can be mimicked in Arabidopsis by treatment with ABA as the authors show that the response is dependent on the PYR/PYL/RCAR-dependent signaling pathway. This response allows roots to respond to the realistically varied microclimate encountered through the soil and offers another excellent example of how using both cereals and Arabidopsis can provide answers that would not be possible from a single experimental system.
Stassen JHM, López A, Jain R, Pascual-Pardo D, Luna E, Smith LM, Ton J (2018) The relationship between transgenerational acquired resistance and global DNA methylation in Arabidopsis. Sci Rep. doi: 10.1038/s41598-018-32448-5
Joost Stassen and Ana Lopez are the lead authors of this study from Juriaan Ton’s lab in Sheffield that continues their work on mechanisms that explain transgenerational acquired resistance (TAR). TAR occurs in the progeny of heavily diseased plants and in this study they investigate the extent of DNA methylation in generations following exposure to pathogens. They find that the extent of TAR-induced methylation was in direct proportion to the number of previous generations that had been exposed to disease. The majority of this methylation was in the CG context in gene bodies and clearly shows that methylation is an important component of molecular changes that occur during TAR.
Gangappa SN, Kumar SV (2018) DET1 and COP1 Modulate the Coordination of Growth and Immunity in Response to Key Seasonal Signals in Arabidopsis. Cell Rep. doi: 10.1016/j.celrep.2018.08.096
Sreeramaiah Gangappa performed this work with Vinod Kumar at the John Innes Centre in which they investigate the molecular pathways that regulate the environmental signals that feed into the balance decision between growth and defense responses. They show that De-Etiolated 1 (DET1) and Constitutive Photomorphogenic 1 (COP1) negatively regulate immunity during favourable growth conditions and that this response is coordinated through the PIF4 transcription factor. These findings lead the authors to conclude that the DET1/COP1-PIF4 module is a key determinant of the different growth requirements that are necessary to response to either environment and disease.
Vőfély RV, Gallagher J, Pisano GD, Bartlett M, Braybrook SA (2018) Of puzzles and pavements: a quantitative exploration of leaf epidermal cell shape. New Phytol. doi: 10.1111/nph.15461
Work from Siobhan Braybrook’s lab features in the Research Roundup for the second consecutive edition, this time led by Roza Vofely at the Sainsbury Lab Cambridge University (SLCU). In this study they have investigated the shape of leaf epidermal pavement cells from a remarkable 278 plant taxa in order to ascertain whether certain lineages are characterized by different cell shapes and whether the presence of an undulating cell wall is common, as in both maize and Arabidopsis. Interestingly they found that these primary examples were the exception as strongly undulating cell walls were unusual. They found that different lineages were characterised by similar levels of undulation and the authors conclude that this study sets a quantitative benchmark on which future experiments can be based that aim to understand the underlying factors that control pavement cell shape.
Martinez-Garcia M, Schubert V, Osman K, Darbyshire A, Sanchez-Moran E, Franklin FCH (2018) TOPII and chromosome movement help remove interlocks between entangled chromosomes during meiosis. J Cell Biol. doi: 10.1083/jcb.201803019
Marina Martinez‐Garcia is the lead author on this work conducted during her time working with Eugenio Sanchez-Moran and Chris Franklin at the University of Birmingham. Normal meiosis requires a lack of structural interlocks between entangled chromosomes that can result from inevitable collisions in an area so packed with nucleic acid. In this paper the authors confirm a previously developed hypothesis that topoisomerase II (TOPII) is needed to remove interlocks. However it is not the only determinant of the number of interlocks as in Arabidopsis mutants in which chromosome movement is reduced, interlocks occur irrespective of the presence of TOPII.
Zhang H, Gannon L, Jones PD, Rundle CA, Hassall KL, Gibbs DJ, Holdsworth MJ, Theodoulou FL (2018) Genetic interactions between ABA signalling and the Arg/N-end rule pathway during Arabidopsis seedling establishment. Sci Rep. doi: 10.1038/s41598-018-33630-5
Hongtao Zhang is the lead author of this work from the lab of Freddie Theodoulou at Rothamsted Research that investigates the role of the PROTEOLYSIS6 (PRT6) N-recognin E3 ligase in the ABA response. PRT6 regulated degradation of Group VII of the Ethylene Response Factor superfamily (ERFVIIs) controls both sugar sensitivity and oil body breakdown in germinating Arabidopsis seedlings. They found that the former but not the latter response was enhanced by ABA signaling components when the ERFVIIs were stabilised. The authors conclude that during seed germination the N-end rule controls multiple layers of regulation, both in an ABA dependent and independent manner