SUMOylation of rice DELLA SLR1 modulates transcriptional responses and improves yield under salt stress.
This work aimed to characterize the molecular differences of SUMO1-SLR1 and SLR1  in rice (Oryza sativa cv. Nipponbare) shoots subjected to salt stress and to identify novel SLR1 interactors.  Because DELLA proteins regulate gene expression, we exposed SLR1-OX, SUMO1SLR1-OX, and Nipponbare genetic background to high salt concentrations (120 mM NaCl) during 8 hours at the seedling stage and collected samples for subsequent RNA-seq analysis. Functional annotation of SLR1-OX DEGs showed enrichment of gene ontology (GO) terms associated with diterpenoid biosynthesis, highlighting the impact of SLR1 on GA metabolism. After functional annotation of DEGs specific to SUMO1SLR1-OX, we found a significant over-representation of GO terms associated with defense response and gibberellin dioxygenase activity. We also found a salt stress-dependent induction of GA20ox2 and GA2ox3 genes in SUMO1SLR1-OX. GA20ox2 and GA2ox3 encode enzymes involved in the regulation of active GA (GA4) levels. Therefore, it is reasonable to hypothesize that SLR1 SUMOylation could adjust active GA homeostasis upon exposure to salt stress.