The effect of SUMOylation on DELLA proteins and abiotic stress responses in Arabidopsis thaliana

• Main Author: Woodcock, Ailidh
• Published: University of Warwick 2014
• Subjects: 570; QK Botany
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.618965

Post-translational modifications are an essential process in all levels of eukaryotic life. Some of these post-translational modifications, such as Ubiquitination, have been researched in great detail whereas the process of SUMOylation was only discovered in the late 1990’s and is less well understood. The DELLA repressors of plant elongation growth have been shown to undergo modification with both Ubiquitin and SUMO, and both the SUMOylation process and DELLA proteins have been linked to responses to abiotic stress in plants. In this project, putative SUMO sites on DELLA proteins RGA and GAI have been mutated to create transgenic lines in which each DELLA becomes non-SUMOylatable. While results for RGA overexpressing lines may require some further investigation, the results for GAIK versus GAIK/R have proven very interesting. With reduced levels of SUMOylation (GAIK/R), there is less restriction of growth in terms of bolting phenotype. In addition, SUMOylation of GAI was demonstrated to have an important role in abiotic stress responses, in terms of primary root growth in Arabidopsis thaliana. Binding data indicates interaction of SUMO with both RGA and GID1a, and although these interactions do not seem to be dependent on GA, they may have influence in preventing degradation of DELLA proteins. Analysis of OTS SUMO protease mutants demonstrates that SUMOylation and deSUMOylation through the OTS protease are necessary for the seed germination process in Arabidopsis, although only at moderate levels. The OTS protease is also demonstrated to have involvement in the seedling establishment process. Overall, this data further reinforces the assertion that SUMOylation is an essential process in plants, and that SUMOylation of DELLA proteins, and many other proteins, is integral to their response to abiotic stress.