CaNAC76 improves cold resistance in pepper by increasing antioxidant capacity and targeting regulation of CaCAD1

Low temperature is the primary environmental factor that restricts the growth, development, and yield of peppers, significantly affecting the growth of the pepper industry. NAC ( N AM, A TAF1/2, and C UC2) transcription factors (TFs) are implicated in plant responses to cold stress, but their specific mechanisms in peppers are unclear. In this study, we isolated a cold-induced NAC transcription factor, CaNAC76, from pepper ( Capsicum annuum L.). CaNAC76 is localized in the nucleus and cytoplasm and exhibits transcriptional activation activity. Silencing CaNAC76 expression reduced the activities of superoxide dismutase, peroxidase, and catalase enzymes, resulting in decreased cold tolerance in peppers. Conversely, overexpressing CaNAC76 increased the activities of antioxidant enzymes in Arabidopsis, enhancing the plant's freezing tolerance. Transcriptional regulation analysis showed that CaNAC76 directly binds to the promoter region of CaCAD1 and induces its expression. Similarly, low temperatures induced the expression of CaCAD1. Overexpression of CaCAD1 enhanced freezing tolerance in Arabidopsis, whereas silencing CaCAD1 expression increased sensitivity to low temperatures. Furthermore, we observed that CaNAC76 overexpression enhanced CAD activity and lignin content in Arabidopsis, leading to lignin deposition in the xylem and interfascicular fibers. In summary, the results demonstrate that CaNAC76 enhances cold tolerance in peppers by increasing the antioxidant capacity and promoting lignin accumulation.