OsbHLH057 targets the AATCA cis-element to regulate disease resistance and drought tolerance in rice.

The AATCA motif was identified to respond pathogens infection in the promoter of defense-related gene Os2H16. OsbHLH057 bound to the motif to positively regulate rice disease resistance and drought tolerance. Sheath blight (ShB), caused by the necrotrophic fungus Rhizoctonia solani, is a devastating disease in rice (Oryza sativa L.). The transcriptional regulation of host defense-related genes in response to R. solani infection is poorly understood. In this study, we identified a cis-element, AATCA, in the promoter of Os2H16, a previously identified multifaceted defense-related gene in rice that responded to fungal attack. Using a DNA pull-down assay coupled with mass spectrometry, a basic helix-loop-helix (bHLH) transcription factor OsbHLH057 was determined to interact with the AATCA cis-element. OsbHLH057 was rapidly induced by R. solani, Xanthomonas oryzae pv. oryzae (Xoo), and osmotic stress. Furthermore, overexpressing OsbHLH057 enhanced rice disease resistance and drought tolerance, while knocking out OsbHLH057 made rice more susceptible to pathogens and drought. Overall, our results uncovered an OsbHLH057 and AATCA module that synergistically regulates the expression of Os2H16 in response to R. solani, Xoo, and drought in conjunction with the previously identified stress-related OsASR2 and GT-1 module.