The miR172a-SNB module orchestrates induced and adult resistance to multiple diseases via MYB30-mediated lignin accumulation in rice

Plants mount induced resistance and adult plant resistance against different pathogens during the whole growth period. Rice production faces threats from multiple major diseases, including rice blast, sheath blight, and bacterial leaf blight. Here we report that a microRNA module, miR172a-SNB-MYB30, regulates induced resistance and adult plant resistance to these three major diseases via lignification in rice. Mechanistically, pathogens induce expression of miR172a, which down-regulates transcription factor SNB to release its suppression on MYB30, leading to an increase in lignin biosynthesis and disease resistance during the whole growth period. Moreover, expression levels of miR172a and MYB30 are gradually increased and consistently correlated with lignin contents and disease resistance during rice development reaching a peak at full maturity stage, whereas SNB RNA levels are reversely correlated with lignin contents and disease resistance, indicating the involvement of the miR172a-SNB-MYB30 module in plant adult resistance. A high conservation exists in the functional domain of SNB protein and its binding sites in the MYB30 promoter among over 4000 rice accessions; moreover, abnormal expression of miR172a, SNB, or MYB30 compromises yield traits, suggesting an artificial selection of the miR172a-SNB-MYB30 module during rice domestication. Our results reveal a novel role for a conserved miRNA-regulated module that significantly contributes to induced and adult resistance against multiple pathogens via lignin accumulation, advancing our understanding in broad-spectrum resistance and adult resistance.