Single-repeat MYB transcription factor, OsMYB1R, enhanced phytoalexin sakuranetin accumulation and Magnaporthe oryzae resistance
Yilin Zhang, Jitao Hu, Linying Li, Xueying Zhang, Lili Chen, Zhongjing Zhou, Junmin Wang, Qing Sheng, Zongsuo Liang, Gaojie Hong, Wei Yu, Yuqing He
Abstract
Sakuranetin, a flavonoid phytoalexin in rice, plays a crucial role in defense against pathogen infection. While MYB-type transcription factors are well-known to regulate plant growth, development, secondary metabolism, and adaptation to environmental stresses, the function of rice MYB-related transcription factors in sakuranetin biosynthesis and sakuranetin-mediated defense remains unclear. In this study, we identified and characterized OsMYB1R, a novel single repeat MYB transcription factor that acts as a transcriptional activator in sakuranetin biosynthesis. Protein-DNA binding and activation assays revealed that OsMYB1R directly regulates the gene promoter of OsNOMT, a key enzyme in sakuranetin synthesis. Molecular analyses and infection studies using OsMYB1R-overexpressing (OsMYB1R-OE) and OsMYB1R-knockout (Osmyb1r, generated using CRISPR/Cas9) plants demonstrated that OsMYB1R increases sakuranetin production and decreases Magnaporthe oryzae infection by transcriptionally regulating OsNOMT expression. This finding indicates a positive regulation of sakuranetin biosynthesis and antifungal resistance by the OsMYB1R-OsNOMT crosstalk. Interestingly, the alteration of OsMYB1R expression did not affect yield-related agronomic traits. Our results reveal a novel and positive role of 1R-MYB in secondary metabolite biosynthesis and pathogen defense, suggesting that OsMYB1R is a potential gene for effectively enhancing rice resistance without compromising yield.