<i>miR444b.2</i>-HsfA1-<i>AOC1</i> module mediates heat priming-enhanced blast resistance in rice.

Abstract

As global climate change exacerbates extreme heat events, the interplay between heat stress and blast disease resistance in rice remains poorly understood. In this study, through integrated transcriptome profiling and systematic phenotyping of mutants in several thermosensory pathways, we identified HsfA1 as a positive regulator of heat priming-enhanced blast resistance in rice. Systematic analysis of microRNA (miRNA) dynamics, bioinformatics prediction, and RNA pull-down experiments revealed that <i>miR444b.2</i>, a temperature-responsive miRNA, directly suppresses the expression of <i>HsfA1</i> by targeting the second exon of <i>HsfA1</i> messenger RNA (mRNA). Genetic analyses demonstrated that heat stress-mediated suppression of <i>miR444b.2</i> expression relieves the repression of <i>HsfA1</i>, thereby enhancing blast resistance in rice. Furthermore, HsfA1 directly binds to the promoter of <i>AOC1</i>, a key jasmonic acid (JA) biosynthesis gene, to activate its expression. Knockout of <i>HsfA1</i> or <i>AOC1</i> abolishes heat priming-enhanced JA accumulation and blast disease resistance, and the phenotypes are largely restored via <i>AOC1</i> overexpression and MeJA treatment. Further identification of <i>HsfA1</i> natural variants and generation of the <i>HsfA1 uORF</i>-edited lines with improved blast resistance offer potential strategies for breeding disease-resistant rice varieties. This study elucidates the <i>miR444b.2</i>-HsfA1-<i>AOC1</i> module that links thermal sensing to JA-mediated blast resistance, providing a molecular blueprint for engineering climate-resilient crops with concurrent biotic-abiotic stress tolerance.