Anti Cyanide Respiration Enhances Low-temperature Tolerance Of Postharvest Plum Fruits Study On The Mechanism Of Membrane Lipid Metabolism And Sugar Metabolism For Improving Flavor Quality

Plum fruits have a short shelf life at room temperature and poor adaptability to low temperatures.Storage temperatures below 7℃can cause chilling damage,resulting in decreased quality and even loss of commercial value.Studying the mechanism of cold damage prevention and control of plum fruits is beneficial for improving the effective application of low-temperature storage technology in post harvest storage of plum fruits.This study investigated the role of cyanide resistant respiration in the occurrence and control of post harvest plum fruit chilling injury.Based on the GO function and KEGG pathway enrichment analysis of the differentially expressed gene in the flesh tissue of the key gene Ps AOX1a in the cyanide resistant respiration pathway,the flavor quality,membrane lipid metabolism,ascorbic acid glutathione(AsA-GSH)cycle,and membrane lipid metabolism of plum fruits treated with pyruvate to activate cyanide resistant respiration during low-temperature storage were studied The key pathways of sugar metabolism were analyzed,and the specific mechanism of enhancing low-temperature tolerance of postharvest plum fruits through cyanide resistant respiration was analyzed from the perspectives of membrane lipid metabolism,reactive oxygen species metabolism,and sugar metabolism.The main research findings are as follows:(1)Pyruvic acid treatment can activate the cyanide resistant respiration pathway of plum fruit by enhancing the activity of alternating oxidase(AOX),a key protein in cyanide resistant respiration,reducing the incidence and index of chilling injury,thereby maintaining the flavor and quality of plum fruit during low-temperature storage.(2)The up regulation of cyanide resistant respiration affected the composition of membrane fatty acids of plum fruits during storage,significantly increased the content of unsaturated fat acids and degree of unsaturation fatty acids(UFA/SFA)in cell membranes,and maintained the fluidity of cell membranes.Pyruvate treatment can increase the activities of lipoxygenase(LOX),lipase(LPS),and phospholipase D(PLD)in plum fruits during low-temperature storage.(3)Upregulation of cyanide resistant respiration promoted the AsA-GSH cycle during plum fruit storage,increased the content of ascorbic acid(AsA),reduced glutathione(GSH),and oxidized glutathione(GSSG),and increased the activities of ascorbic acid peroxidase(APX),monodehydroascorbic acid reductase(MDHAR),dehydroascorbic acid reductase(DHAR),and glutathione reductase(GR),which is conducive to the improvement of antioxidant capacity.(4)Upregulation of cyanide resistant respiration increased the content of fructose and sorbitol during storage of plum fruits,promoted the hydrolysis of sucrose,increased the activity of NAD+-sorbitol dehydrogenase(NAD~+-SDH),slowed down the increase of sucrose lyase(SS-I)activity,and 5 m M pyruvate increased the activities of sucrose synthase(SS-II)and NADP+-sorbitol dehydrogenase(NADP~+-SDH),which is beneficial for increasing the sugar content in plum fruits.(5)RT qPCR analysis showed that the key genes Ps ADH1,Ps MIOX,Ps KCS and transcription factors Ps ERF,Psb HLH,Ps MYB of membrane lipid metabolism,antioxidant metabolism and glucose metabolism in plum fruits treated with pyruvate under low temperature stress were up-regulated,which was the same as the results of transcriptome analysis.This was an anti stress response of plum fruits to low temperature stress.