OsMYB133 regulates sakuranetin biosynthesis to enhance blast resistance in rice. 2. OsMYB133 directly acted on OsNOMT gene promoter to activated its expression. 3. OsMYB133 positively regulates momilactone biosynthesis to elevate chemical defense in rice. Sakuranetin is the flavonoid phytoalexin to defense blast pathogen infection in rice ( Oryza sativa L.). Although sakuranetin biosynthesis has been characterized, the transcriptional regulation of sakuranetin biosynthetic genes remains elusive. A transcription factor OsMYB133 is identified here to coexpress with sakuranetin biosynthetic gene OsNOMT and exhibits highly inducible expression in response to the infection of blast fungus Magnaporthe oryzae . Overexpression of OsMYB133 elevated blast resistance and knockout lines showed more susceptible to M. oryzae infection. OsMYB133 directly bound to the OsNOMT gene promoter and enhanced its gene expression, leading to increased sakuranetin accumulation and blast resistance. OsMYB133 also directly regulates momilactone biosynthesis genes OsKSL4 and OsCYP99A3 to increase corresponding gene expression and momilactone accumulation in the overexpression rice line. This study identified the OsMYB133 as the key transcription factor to regulate flavonoid and diterpenoid phytoalexin biosynthesis and provided the insights for comprehensive characterization of chemical defense mechanism and molecular breeding to increase pathogen resistance in rice.
Sha et al. (2026) studied this question.