Genome-wide transcriptome analysis of Arabidopsis and siz1-3 response to drought stress

Post-translational modifications of proteins by Small Ubiquitin-like Modifiers (SUMOs) regulate protein degradation and localization, protein-protein interaction, and transcriptional activity. SUMO E3 ligase functions are executed by SIZ1/SIZ2 in yeast and PIAS family members in human. The Arabidopsis genome contains only one gene, SIZ1, that is orthologous to yeast SIZ1/SIZ2. Here, we show that the Arabidopsis SIZ1 interacts with SUM1 and SCE1a, the SUMO E2 conjugating enzyme. Compared to WT, the null mutant siz-1-3 is smaller in statue because of reduced expression of gene involved in brassinosteroid biosynthesis and signalling. Drought stress induces the accumulation of SUMO-protein conjugates, which is in part dependent on SIZ1 but not on ABA. Mutant plants of siz1-3 have significant lower tolerance to drought stress. Genome wide expression analysis identified about 2,000 Arabidopsis genes that are responsive to drought, and SIZ1 mediates the induction of 600 of these genes by a pathway independent of DREB2A and ABA. SIZ1-dependent, drought-responsive genes include those encoding enzymes of the anthocyanin synthesis pathway and jasmonate response. From these results, we conclude that SIZ1 regulates Arabidopsis development and plays a role in drought stress response probably through the control of gene expression.

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Catala R, Ouyang J, Abreu IA, Hu Y, Seo H, Zhang X, Chua NH