The bHLH transcription factor AhbHLH36 enhances salt tolerance via the activation of AhCAT in peanut

Basic helix-loop-helix (bHLH) transcription factor family members constitute one of the largest families of transcription factors (TFs) in plants and play important roles in abiotic stress responses. However, the roles of these TFs in peanut are largely unknown. Previously, it was reported that a typical bHLH TF, AhbHLH36, might positively regulate salt stress in peanut. Herein, this research determined that AhbHLH36 functions as a transcriptional activator in peanut to increase tolerance to salt stress. AhbHLH36 was rapidly induced by salt stress, and its protein was localized to the nucleus and exhibited transactivation activity in yeast cells. The overexpression of AhbHLH36 in Arabidopsis increased salt tolerance. Transient overexpression of AhbHLH36 in peanut also improved salt tolerance, whereas AhbHLH36-silenced samples presented increased sensitivity to salt stress. Subsequent investigations revealed that the overexpression of AhbHLH36 could results in increased activities of antioxidant enzymes (peroxidase, catalase and superoxide dismutase) under salt conditions. Further analysis revealed that AhbHLH36 protein only directly interacted with the AhCAT gene promoter and positively activates its expression. This research reveals an emerging mechanism by which AhbHLH36 contributes to improving salt resistance in peanut and presents potential genetic targets for breeding peanut cultivars that are tolerant to salt, which impairs peanut growth, development, and productivity.