Biosynthesis of sakuranetin regulated by OsMPK6-OsWRKY67-OsNOMT cascade enhances resistance to false smut disease.

Rice false smut disease, caused by the fungal pathogen Ustilaginoidea virens, significantly restricts both the production and quality of rice grains. However, the molecular mechanism underlying rice resistance against U. virens remain largely elusive. Transcriptome analysis of rice panicles infected with U. virens revealing the crucial role of genes involved in sakuranetin biosynthesis in conferring resistance to the pathogen. In vitro assays demonstrated that sakuranetin was most effective at inhibiting mycelial growth, spore germination, and host infection by U. virens. The expression of OsNOMT, the key enzyme in sakuranetin biosynthesis, is directly regulated by the transcription factor OsWRKY67. Furthermore, OsMPK6, a mitogen-activated protein kinase, interacts with and phosphorylates OsWRKY67, thereby modulating sakuranetin biosynthesis and resistance to U. virens. Moreover, the exogenous application of synthetic sakuranetin significantly reduces U. virens infection. Our findings reveal that the OsMPK6-OsWRKY67-OsNOMT signaling cascade plays a pivotal role in rice resistance to U. virens by regulating sakuranetin biosynthesis.