OsERF7 Negatively Regulates Resistance to Sheath Blight Disease by Inhibiting Phytoalexin Biosynthesis

Abstract

Ethylene response factors (ERFs) are plant transcription agents that play a pivotal role in disease resistance through the ethylene signaling pathway. However, whether and how ERFs regulate resistance to sheath blight (ShB), caused by Rhizoctonia solani in rice, remains largely unknown. Here, we demonstrated that OsERF7 negatively regulates rice resistance to ShB by inhibiting phytoalexin biosynthesis. Overexpression of OsERF7 (OsERF7OE) significantly decreased ShB resistance, whereas knockout of OsERF7 (oserf7) enhanced it. Mechanistically, antioxidant enzyme activities are significantly reduced in OsERF7OE plants, but increased in oserf7 plants. Furthermore, transcriptome analysis revealed that oserf7 plants exhibited significant upregulation of pathogenesis-related (PR) and phytoalexin biosynthesis genes upon R. solani infection. Consistently, transcript levels of phytoalexin biosynthesis genes, including OsKSL7, OsKSL8, OsKOL5, and OsCPS4, were significantly elevated in oserf7 plants, but reduced in OsERF7OE plants in response to R. solani infection. Electrophoretic mobility shift assays and dual-luciferase (LUC) reporter assays further confirmed that OsERF7 directly binds to the promoters of OsKSL8, OsKOL5, and OsCPS4, thereby repressing their expression. In summary, our study revealed that OsERF7 negatively regulated rice resistance to ShB primarily by inhibiting phytoalexin biosynthesis.