MicroRNA775 and target Galactosyltransferase (GALT9) module regulates recovery from submergence induced senescence by modulating SAGs in Arabidopsis thaliana

Submergence induced hypoxic condition is one of the abiotic stresses which negatively affects the plant growth and development, and causes early onset of senescence. Hypoxic conditions ateres the expression of a number of non-coding microRNAs (miRNAs), besides protein-coding genes. However, the molecular function of stress-induced miRNA in submergence induced physiological or developmental changes and recovery remains to be understood. The expression of miR775 is highly induced under hypoxic stress conditions. Here, we show that miR775 is a potential post-transcriptional regulator number of targets, including Galactosyltransferase (GALT9). The expression of miR775 and target GALT9 was significantly induced and reduced respectively at 24 hours of submergence. The overexpression of miR775 (miR775-Oe) confers enhanced recovery from submergence stress and reduced accumulation of ROS, in contrast to wild type and endogenous target mimic of miR775 (MIM775) Arabidopsis plants. We observed a similar recovery phenotype in case of target galt9 mutant plants, indicating the role of miR775-GALT9 module in recovery from submergence. Further, we showed that the expression of SENESCENCE ASSOCIATED GENES (SAGs), such as SAG12, SAG29, and ORE1, was increased in MIM775 and reduced in miR775-Oe and galt9 plants. Thus, our results suggest that miR775-GALT9 module plays a crucial role in the recovery from submergence by modulating the expression of SAGs through differential accumulation of ROS.