SUMO protease GmOTSa positively regulates drought tolerance in transgenic tobacco and soybean hairy roots

SUMO protease is important for regulating the balance of SUMOylation and deSUMOylation. Despite the in-vestigations of several SUMO protease genes in model plants, to date, the biological functions of these regulatory enzymes in soybean have yet to be ascertained. In the present study, a SUMO protease GmOTSa was identified in soybean, and was localized in the nucleus with the bona fide SUMO protease activity both in vitro and in vivo. Further RT-qPCR analysis showed that GmOTSa was expressed in various tissues and was highly induced by PEG treatment. We demonstrated that GmOTSa conferred drought tolerance in tobacco plants by increasing the germination rate, the fresh and dry weights upon water deficit, and improving the survival rate after rewatering. Overexpression of GmOTSa gene in tobacco lines and soybean hairy roots enhanced drought tolerance by positively regulating ROS scavenging, thus maintained lower ROS content. Moreover, less MDA content and higher total chlorophyll content as well as promoted closure of stomata were detected in the OE plants than in the WT plants in response to drought stress. Conversely, soybean hairy roots with simultaneous knockout of GmOTSa and the homologous gene GmOTSb using the CRISPR-Cas9 method exhibited reduced drought toler-ance. Correspondingly, the expression of drought-related genes showed greater induction upon drought stress in the GmOTSa-overexpressed lines. Overall, these results indicated that GmOTSa may act as a positive regulator of drought responses and therefore could be considered a potential gene for the genetic improvement of drought tolerance.