Just three papers in this weeks Arabidopsis Research Roundup and they each cover fundamental aspects of the hormone and environmental control of gene expression. First Keith Lindsey provides an audio description of work that aims to dissect the complex hormonal regulation of root growth while secondly, Nick Harberd is involved in a study that investigates the HY5 shoot-root signaling protein. Finally Ian Graham leads a study into factors that regulate seed dormancy.
Rowe JH, Topping JF, Liu J, Lindsey K (2016) Abscisic acid regulates root growth under osmotic stress conditions via an interacting hormonal network with cytokinin, ethylene and auxin New Phytol. http://dx.doi.org/ 10.1111/nph.13882 Open Access
Keith Lindsey (Durham) is the corresponding author for this study that investigates the complex hormonal network that regulates the Arabidopsis root response to osmotic stress. The effect of ABA, cytokinin and ethylene on auxin transport are assessed through changes in the dynamics of PIN protein expression. Unsurprisingly they discover a wide range of effects transmitted via crosstalk between these four hormones and that these effects act in a tissue specific manner, as the expression of PIN1 (in the vascular tissue) and PIN2 (in the lateral root cap and epidermis) are altered in different ways. Ultimately the authors conclude that the classic ‘stress hormone’ ABA regulates the root response to drought together with auxin, ethylene and cytokinin in a complex signaling network.
Keith has kindly supplied a brief audio description of this work.
Chen X, Yao Q, Gao X, Jiang C, Harberd NP, Fu X (2016) Shoot-to-Root Mobile Transcription Factor HY5 Coordinates Plant Carbon and Nitrogen Acquisition http://dx.doi.org/10.1016/j.cub.2015.12.066
GARNet committee member Nick Harberd (Oxford) is the UK representative on this Chinese-led study that investigates the mode of action of the mobile transcription factor ELONGATED HYPOCOTYL5 (HY5). It has been long known that HY5, a bZIP TF, regulates growth responses to light and in this study the authors demonstrate that HY5 controls light-regulated root growth and nitrate uptake. Remarkably, HY5 from the shoot can activate root-derived HY5, in turn switching on the nitrate transporter NRT2.1. This response involves a mechanism that senses carbon:nitrogen balance across different light conditions, thus placing HY5 as a key regulator in the whole-plant response to changing environmental conditions.
Dave A, Vaistij FE, Gilday AD, Penfield SD, Graham IA (2016) Regulation of Arabidopsis thaliana seed dormancy and germination by 12-oxo-phytodienoic acid Journal of Experimental Botany http://dx.doi.org/10.1093/jxb/erw028 Open Access
This paper results from a collaboration between the labs of Ian Graham (CNAP, York) and Steve Penfield (John Innes Centre) and features an investigation into factors that regulate seed germination. Previously it was known that oxylipin 12-oxo-phytodienoic acid (OPDA) acts together with ABA to regulate germination but this study elucidates that OPDA specifically acts via the ABI5 and RGL2 hormone-regulated proteins. Furthermore the OPDA-ABA signal also acts via another dormancy promoting factor, MOTHER-OF-FT-AND-TFL1 (MFT). Therefore maintenance of dormancy in Arabidopsis seedlings is regulated by ABA and MFT promoting the accumulation of OPDA, highlighting this as a critical control point in this complex process.