Rapeseed NAC46 positively regulates hypersensitive response-like cell death and chlorophyll degradation

Abstract

Plants are frequently challenged by various stresses, such as abiotic and biotic stresses. The NAC (NAM/ATAF/CUC) transcription factor family is specific to plants and play diverse roles including resistance to abiotic and biotic stresses, while the functions of many rapeseed (Brassica napus L.) NACs are still unknown. In this study, we identified that rapeseed NAC46 positively regulated hypersensitive response (HR) -like cell death. BnaNAC46 expression was induced by multiple stress and phytohormone treatments and was highly expressed in senescent leaves. BnaNAC46 localized in the nucleus and showed transcriptional activation activity in both yeasts and plant cells. BnaNAC46 bound to a cis-element of NACBS (NAC binding sequence). Overexpression of BnaNAC46 resulted in HR-like cell death and chlorophyll degradation. Results of dual luciferase, gel shift and chromatin immunoprecipitation coupled to qPCR assays have demonstrated that BnaNAC46 directly bound to promoters of BnaBFN1, BnaCEP1, BnaMC9, BnaγVPE, BnaNYE1 and BnaPPH genes implicated in programmed cell death and chlorophyll degradation, via the NACBS element. In summary, this study has revealed that rapeseed NAC46 is a transcriptional activator that acts as a positive regulator of cell death and chlorophyll degradation.