bZIP23 interacts with NAC028 to modulate rice resistance to sheath blight disease

Abstract

Rice sheath blight disease (ShB) is a serious threat to rice production, and breeding ShB-resistance varieties is the most effective strategy for ShB control. However, the molecular mechanisms of rice resistance to ShB are largely unknown. In this study, the NAC transcription factor NAC028 was shown to be sensitive to ShB infection. ShB inoculation assays revealed that NAC028 is a positive regulator of ShB resistance. To elucidate the molecular basis of NAC028-mediated ShB resistance, another transcription factor (bZIP23) was identified as a NAC028-interacting protein. Results of the transcriptome and qRT-PCR analyses demonstrated that CAD8B, a key enzyme for lignin biosynthesis and ShB resistance, is regulated by both bZIP23 and NAC028. The combination of the yeast-one hybrid, ChIP-qPCR, and transactivation assays illustrated that both bZIP23 and NAC028 directly bind the CAD8B promoter and activate its expression. The transcriptional connection between bZIP23 and NAC028 was also investigated and the results of in vitro and in vivo assays demonstrated that NAC028 was one of the target genes of bZIP23, but not vice versa. The results presented here provide new insights into the molecular basis of ShB resistance and contribute to the potential targets for the ShB resistance breeding program.

Keywords: Lignin; NAC028; Resistance; Rice sheath blight; Transcription factor; bZIP23.