Abstract

High-temperature (HT) stress during flowering causes male sterility and yield loss in soybean. MYB transcription factors are key regulators under abiotic stress, yet their function and mechanism in regulating male fertility under HT stress in soybean are not fully understood. In this study, a MYB transcription factorGmMYB21ain soybean was identified.GmMYB21awas induced by HT stress in soybean restorer line and was specifically expressed in pollen. Through overexpression and knockout experiments, we demonstrated thatGmMYB21apositively regulated pollen viability and germination under HT stress. Overexpression ofGmMYB21asignificantly enhanced these traits in restorer line, whereas knockout plants exhibited the opposite effect. Transcriptome sequencing revealed thatGmMYB21aoverexpression upregulated numerous stress-responsive genes, particularly those involved in flavonoid biosynthesis and sugar metabolism. In addition, molecular experiments confirmed that GmMYB21a bound to the promoter of flavonoid synthesis geneGmCHI2-Aand promoted its expression. In summary, our research indicatedGmMYB21aenhanced the HT-tolerance of male fertility in soybean restorer line through reactive oxygen species scavenging and flavonoid synthesis. This study aims to elucidate the thermotolerance mechanism in soybean male fertility and identify genetic resources for breeding HT-tolerant restorer lines.