stu-miR159a negatively regulates anthocyanin-specific MYB transcription factor to mediate drought stress tolerance in potato

MicroRNAs (miRNAs) are a class of small endogenous non-coding RNAs that direct post-transcriptional gene silencing. In plants, numerous miRNAs have been demonstrated to be regulated under drought-induced stress. However, the role of miRNAs in drought regulation remains unclear in potato. In this work, the function of stu-miR159a was investigated in responding to drought stress in potato. Upon examination, StGAMyb-like1 was identified as the target gene for stu-miR159a. Overexpression of stu-miR159a (stu-miR159a OE plants) increased sensitivity to drought, interference with stu-miR159a activity by target mimics (stu-miR159a ST plants) resulted in drought resistance. During drought treatment, the target gene StGAMyb-like1 showed increased activation in stu-miR159a ST plants compared to non-transgenic plants. In contrast, drought stress induced weaker activation of the target gene in stu-miR159a OE plants. In stu-miR159a ST plants, the expression of critical genes in the anthocyanin biosynthesis pathway (StF3′5′H, StF3′H and StCHS2) was increased by decreasing stu-miR159a activity and simultaneously increasing that of StGAMyb-like1. Meanwhile, with drought treatment, stu-miR159a ST plants exhibited higher anthocyanin accumulation than non-transgenic ones, indicating enhanced antioxidant capacity and improved drought tolerance. The above data support that stu-miR159a is a negative regulator of drought stress and provide new insights into the stu-miR159a-mediated regulation of the anthocyanin biosynthesis pathway in controlling drought tolerance in potato.