6th Oct 2016

This week Arabidopsis Research Roundup includes an audio description from Robert Sablowski about work from this lab that describes the early specification of stem tissue within the shoot apical meristem. In addition multiple members of CPIB in Nottingham are involved in two connected papers that describe how auxin homeostasis is controlled at the cell and tissue level. Researchers from the University of Bristol shed light on the relationship between viral infection and stomatal development whilst Claudius Marondedze from the University of Cambridge in involved in a study that has used next generation lighting technology to grow Arabidopsis. Finally Sean May from NASC is a co-author on a study that looks into the role of brassinosteroid on the response to freezing temperatures.

Bencivenga S, Serrano-Mislata A, Bush M1, Fox S, Sablowski R (2016) Control of Oriented Tissue Growth through Repression of Organ Boundary Genes Promotes Stem Morphogenesis. Dev Cell. S1534-5807(16)30588-3 Open Access

Robert Sablowski (John Innes Centre) is the lead author on this study that investigates the origin of Arabidopsis stem tissue within the shoot apical meristem (SAM). They show that the transcription factor REPLUMLESS (RPL) is responsible for patterning in the central and peripheral regions of the Rib Zone, which is a subset of cells within the SAM. The authors identify genes that are targeted by RPL, including LIGHT-SENSITIVE HYPOCOTYL 4 that had been previously identified as an organ boundary gene and in this context is involved in the same signaling pathway as RPL. This work opens up new avenues to research stem development, which is a critical yet little studied aspect of plant growth.

Professor Sablowski kindly provides an audio description of this work.

Last year Robert collaborated with Maddie Moate to produce an excellent video about meristems!

Porco S, Pěnčík A, Rashed A, Voß U, Casanova-Sáez R, Bishopp A, Golebiowska A, Bhosale R, Swarup R, Swarup K, Peňáková P, Novák O, Staswick P, Hedden P, Phillips AL, Vissenberg K, Bennett MJ, Ljung K (2016) Dioxygenase-encoding AtDAO1 gene controls IAA oxidation and homeostasis in Arabidopsis. PNAS Open Access

Mellor N, Band LR, Pěnčík A, Novák O, Rashed A, Holman T, Wilson MH, Voß U, Bishopp A, King JR, Ljung K, Bennett MJ, Owen MR (2016) Dynamic regulation of auxin oxidase and conjugating enzymes AtDAO1 and GH3 modulates auxin homeostasis. PANS 10.1073/pnas.1604458113 Open Access

Malcolm Bennett and colleagues at CPIB in Nottingham are authors on back-to-back manuscripts in PNAS that investigate the control of auxin metabolism and homeostasis. Both papers focus on the role of the DIOXYGENASE FOR AUXIN OXIDATION 1 (AtDAO1) gene in this process. AtDAO1 is a highly expressed IAA oxidase that, when disrupted, causes significant changes in the steady state levels of oxIAA and IAA conjugates, but not IAA itself, which may explain why the atdao1 mutant has a relatively mild phenotype. AtDAO1, along with the GH3 IAA-conjugating enzymes are auxin-inducible, demonstrating that these proteins play a role in auxin homeostasis that is dependent on the prevailing auxin concentration.

The second paper develops a mathematical model for the interactions between AtDAO1, the GH3 enzymes, the relationship between auxin biosynthesis and conjugation and how these changes occur at different auxin concentrations. In addition they extend this homeostasis model into a multicellular environment demonstrating that the role of AtDAO1 differs across root tissues in a manner that is predicted by the mutant phenotype.

Murray RR, Emblow MS, Hetherington AM, Foster GD (2016) Plant virus infections control stomatal development. Sci Rep. Open Access

Gary Foster and Alistair Hetherington at the University of Bristol are the lead authors on this study that demonstrates that plant viral infections affect stomatal development in both Nicotiana tabacum and Arabidopsis thaliana. In both cases susceptible, but not resistant, plants showed a lower stomatal index (stomatal density / stomatal density+epidermal cell density) whilst the stomatal density was reduced in susceptible Arabidopsis plants. This preliminary study provides evidence for a relationship between viral infection and stomatal development that will undoubtedly lead to many other studies on this topic.

Ooi A, Wong A, Ng TK, Marondedze C, Gehring C, Ooi BS (2016) Growth and development of Arabidopsis thaliana under single-wavelength red and blue laser light. Sci Rep Open Access

This Saudi-Arabia based study includes Claudius Marondedze from the University of Cambridge and uses Arabidopsis as a model to understand mechanisms of growth that are important in the development of indoor horticulture. These experiments involve growing Arabidopsis under high-powered single-wavelength lasers and show that they grow normally from seed to seed. The authors perform a proteomic analysis and show that these plants have lower expression of proteins involved in light and radiation stress. Therefore this study offers an insight into the potential of using this next generation lighting technology for future horticultural applications.

Eremina M, Unterholzner SJ, Rathnayake AI, Castellanos M, Khan M, Kugler KG, May ST, Mayer KF, Rozhon W, Poppenberger B (2016) Brassinosteroids participate in the control of basal and acquired freezing tolerance of plants. PNAS

This German-led study includes GARNet Committee member and NASC Director Sean May and looks into the role of brassinosteroids in the control of freezing tolerance in Arabidopsis. BR-response mutants are hypersensitive to freezing while constitutive BR signaling provides enhanced freezing tolerance. This study shows that this BR effect is mediated via well-known C-REPEAT/DEHYDRATION-RESPONSIVE ELEMENT BINDING FACTOR (CBF) proteins but also through CBF-independent signaling. Finally the authors provide a model to explain the role of BR during the response to freezing stress.