OsWRKY9 is Involved in Transcriptional Regulatory Cascade Enhancing Broad-Spectrum Disease Resistance

Diverse pathogens, including Fusarium fujikuroi and Xanthomonas oryzae pv. oryzae (Xoo), cause significant yield losses in rice (Oryza sativa). The situation is expected to worsen due to rapid climate change. Thus, identifying novel genes conferring innate immunity against these pathogens is crucial for global food security. WRKY transcription factors are involved in various plant processes, including innate immunity. In rice, there are 125 OsWRKYs, with some functions reported. However, the roles of many OsWRKYs in rice immunity remain largely unknown. In this study, we investigate the role of OsWRKY9 in broad-spectrum disease resistance. OsWRKY9 transcripts increased in response to F. fujikuroi and Xoo. The promoter of OsWRKY9 was indirectly activated by OsWRKY65, which confers broad-spectrum resistance to F. fujikuroi and Xoo. Moreover, OsWRKY9-overexpressing transgenic plants exhibited enhanced resistance to both pathogens in a manner similar to transgenic plants overexpressing OsWRKY65. Additionally, OsWRKY9 modulated the expression of various defense-related genes regulated by OsWRKY65. These results indicate that the OsWRKY65-OsWRKY9 module enhances resistance to bakanae disease and bacterial blight.