Transcription factor CaNAC1 regulates low-temperature-induced phospholipid degradation in green bell pepper

Abstract Phospholipids constitute the main component of biomembranes. During low-temperature storage and transportation of harvested bell peppers, chilling injury participates in pepper decay. A primary cause of pepper chilling injury is phospholipid degradation. In this study, three phospholipase D (PLD)-encoding genes were identified from bell peppers and their activity were analyzed under cold stress. Low temperatures induced strong accumulation of the CaPLDα4 transcript, suggesting that this induction contributes to the phenomenon of phospholipid degradation and cell membrane destruction at 4°C. Low temperatures also significantly induced the transcript amounts of NAM-ATAF1/2-CUC2 (NAC) domain transcription factor. CaNAC1 was found to possess the capacity to interact with the promoter of CaPLD4 in a yeast one-hybrid screen. Furthermore, electrophoretic mobility shift and ß-glucuronidase reporter assays demonstrated that CaNAC1 binds to the CTGCAG motif in the CaPLDα4 promoter, thereby activating its transcription and controlling phospholipid degradation. The ubiquitination sites of the CaNAC1 protein were also characterized by liquid chromatography tandem-mass spectrometry. In conclusion, CaNAC1 is a transcriptional activator of CaPLDα4 and is suggested to participate in membrane lipid degradation of bell peppers when stored at low temperature.