Low temperatures are known to destroy cell membranes’ structural integrity by affecting the remodeling of their phospholipids. Fruits stored at low temperature are prone to chilling injury, characterized by discoloration, absence of ripening, surface pitting, growth inhibition, flavor loss, decay, and wilting. Phosphatidic acid, a vital second-messenger lipid in plants, is known to accumulate in response to different kinds of stress stimuli. However, the regulatory mechanism of its production from the degradation of phospholipids remains poorly understood. We identified two cold-responsive NAC (NAM/ATAF1/CUC2) transcription factors from bananas, namely, MaNAC25 and MaNAC28, which negatively regulated cold tolerance in banana fruits by upregulating the expression of phospholipid degradation genes in banana fruits. Furthermore, MaNAC25 and MaNAC28 formed a positive feedback loop to induce phospholipid degradation and produce phosphatidic acid. In contrast, ethylene directly inhibited the degradation of phospholipids in banana and transgenic tomato fruits. In addition, ethylene reduced the activity of MaNAC25 and MaNAC28, thereby inhibiting phospholipid degradation. To conclude, NAC-mediated membrane lipid remodeling negatively regulates the cold tolerance of banana and transgenic tomato fruits.

中文翻译：

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NAC介导的膜脂重塑负调控水果耐寒性

已知低温会通过影响其磷脂的重塑来破坏细胞膜的结构完整性。低温贮藏的果实易发生冷害，表现为变色、不熟、表面麻点、生长抑制、风味丧失、腐烂、萎蔫等。已知磷脂酸是植物中一种重要的第二信使脂质，它会响应不同种类的压力刺激而积累。然而，其从磷脂降解中产生的调节机制仍然知之甚少。我们从香蕉中鉴定出两种冷响应 NAC (NAM/ATAF1/CUC2) 转录因子，即 MaNAC25 和 MaNAC28，它们通过上调香蕉果实中磷脂降解基因的表达来负调控香蕉果实的耐寒性。此外，MaNAC25 和 MaNAC28 形成正反馈回路以诱导磷脂降解并产生磷脂酸。相比之下，乙烯直接抑制香蕉和转基因番茄果实中磷脂的降解。此外，乙烯降低了 MaNAC25 和 MaNAC28 的活性，从而抑制了磷脂降解。综上所述，NAC 介导的膜脂重塑负向调节香蕉和转基因番茄果实的耐寒性。