Rice microRNA171f/SCL6 module enhances drought tolerance by regulation of flavonoid biosynthesis genes.

Plants have evolved sophisticated defense systems to enhance drought tolerance. These include the microRNA (miRNA) group of small noncoding RNAs that act as post-transcriptional regulators; however, details of the mechanisms by which they confer drought tolerance are not well understood. Here, we show that osa-MIR171f, a member of osa-MIR171 gene family, is mainly expressed in response to drought stress and regulates the transcript levels of SCARECROW-LIKE6-I (SCL6-I) and SCL6-II in rice (Oryza sativa). The SCL6 genes are known to be involved in shoot branching and flag leaf morphology. Osa-MIR171f-overexpressing (osa-MIR171f-OE) transgenic plants showed reduced drought symptoms compared with non-transgenic (NT) control plants under both field drought and polyethylene glycol (PEG)-mediated dehydration stress conditions. Transcriptome analysis of osa-MIR171f-OE plants and osa-mir171f-knockout (K/O) lines generated by clustered regularly interspaced short palindromic repeats (CRISPR/Cas9) revealed that osa-mature-miR171a-f (osa-miR171) regulates the expression of flavonoid biosynthesis genes, consequently leading to drought tolerance. This upregulation in the osa-MIR171f-OE plants, which did not occur in NT control plants, was observed under both normal and drought conditions. Our findings indicate that osa-miR171 plays a role in drought tolerance by regulating SCL6-I and SCL6-II transcript levels.