The safflower bHLH transcription factor CtbHLH41 negatively regulates SA-induced leaf senescence through interaction with CtCP1

Salicylic acid (SA) plays an important role in regulating leaf senescence. However, the molecular mechanism of leaf senescence of safflower ( Carthamus tinctorius ) is still elusive. In this study, we found that the bHLH transcription factor (TF) CtbHLH41 in Carthamus tinctorius significantly delayed leaf senescence and inhibited the expression of senescence-related genes. In order to explore how CtbHLH41 promotes leaf senescence, we carried out yeast two-hybrid screening. In this study, by exploring the mechanism of CtbHLH41 regulating CtCP1 , it was found that CtCP1 promoted the hydrolysis of CtbHLH41 protein, accelerated the transcriptional activities of salicylic acid-mediated senescence-related genes CtSAG12 and CtSAG29 , chlorophyll degradation genes CtNYC1 and CtNYE1 , and accelerated leaf senescence. We found a negative SA regulator CtANS1 , which interacted with CtbHLH41 and regulated its stability, thereby inhibiting CtCP1 -mediated leaf senescence. In short, our results provide a new insight into the mechanism of CtbHLH41 actively regulating the senescence of safflower leaves induced by SA. • In the course of our research on CtbHLH41 , we found that the overexpression of CtbHLH41 slowed down leaf senescence. • CtCP1 was included in the results of CtbHLH41 screening by yeast two-hybrid, which may promote leaf senescence of plants. • We found that CtCP1 promoted the hydrolysis of CtbHLH41 protein and accelerated leaf senescence. • We also found a gene CtANS1 , which also interacts with CtbHLH41 , thereby delaying leaf senescence caused by CtCP1 .