Regulation By Nitric Oxide And Chilling Signal On Fatty Acid Metabolism And Phase Transition Temperature In Cell Membrane Of Peaches

Cell membrane can regulate many physiological processes such as the conversion of substance,signal transmission and protein synthesis.Cell membrane can separate cell contents from the surrounding environment,maintain the structural stability of organelles and subcellular structures.Low temperature can lead to the transition of membrane lipid from liquid crystal state to gel state,cause the fatty acid chains changing from order to disorder,and then promote the metabolic disturbance of cells,produce a large amount of toxic substances,result in chilling injury of fruits.As a gaseous signal molecule,nitric oxide?NO?plays signaling roles in physiological processes.Exogenous NO improves fruit cold tolerance,delay fruit senescence,and increase fruit storage quality.There are interactions between NO and cold signal in plants.However,the effects of NO and cold signal on fatty acid metabolism and phase transition behavior are rarely reported.In this study,Feicheng peaches were treated with 15?mol L^-1NO solutions,5?mol L^-1c-PTIO solution and double distilled water,and then stored at 0oC and 25oC respectively.The regulation of NO and cold stress on fatty acid metabolism and phase transition behavior of cell membrane were studied.The results showed that NO increased the activities of acetyl-CoA carboxylase?ACCase?and phosphatidate phosphatase?PPase?,so as to increase the total fatty acid content of peaches.NO increased fatty acid synthetase?FAS?activity to increase the ratio of polyunsaturated fatty acids.At the same time,NO reduced chilling injury,increased the cell membrane fluidity of peach fruit.NO changed the fluorescence quantum yield by changing the physical state of the cell membrane,reduced the phase transition temperature of the membrane lipid.The occurrence of phase transition would shift the peak positions of methylene antisymmetric and symmetric stretching vibration absorption peaks(v_asCH₂ and v_sCH₂).In addition,NO increased the content of hormones in peaches during storage.Among them,abscisic acid?SA?and abscisic acid?ABA?were related to the stomatal closure and protected the integrity in fruit cell membrane.Indole-3-acetic acid?IAA?had a negative correlation with cold tolerance.NO increased IAA content in fruits and reduced cold injury of fruits.The content of gibberellin?GA₃?was related to the transition temperature of membrane lipids.NO increased the content of GA₃,decreased the temperature of cell membrane phase transition,and kept the fluidity better,thus reduced chilling injury of peaches during storage.The interaction between NO and cold signal could maintain high cold-resistance of peaches.The iTRAQ results suggested that 101 proteins were related to the membrane lipid metabolism.GO and COG analysis showed that the most proteins mainly involved in fatty acid degradation,fatty acid biosynthesis,fatty acid elongation,unsaturated fatty acid synthesis,linoleic acid metabolism,arachidic acid metabolism and?-linolenic acid metabolism.NO up-regulated the key protein of lipid metabolism,reduced the effect of low temperature on membrane lipid metabolism related proteins to adapt the cold resistance.The regulation by NO on the differential proteins was more obvious at low temperature than at room temperature.These results suggested that the interaction of NO and cold signal could reduce the chilling injury degree of peach fruit at low temperature,regulate lipid metabolism and phase transition,prolong the storage of peaches.