The Molecular Mechanism Of Gibberellin Deficiency On Cold Tolerance Of Postharvest Tomato Fruit

Chilling injury?CI?is a type of physiological disorder of cold sensitive fruit such as tomato fruit that occur after low temperature storage,which can shorten the shelf life of fruit and vegetables and cause serious economic losses.Gibberellins?GAs?,as significant plant hormones,play an important role in regulating the whole life cycle of higher plants,e.g.,promoting cell elongation and division,stimulating organ growth and participating in the regulation the response to biological and abiotic stress.Researches have shown that exogenous GA₃ treatment can effectively improve the cold tolerance of postharvest fruit and vegetable.However,the molecular mechanism of GA regulate chilling resistance response of fruits and vegetables is still unclear.Tomato?Solanum lycopersicum L.?is a typical cold sensitive vegetable and used as a model plant for CI research.In this study,wild type?WT??Solanum lycopersicum L.cv.Moneymaker?and GA-deficient mutant?gib-3?tomato fruits at the mature green stage were used as experimental materials and stored at 4?for 28 days.Through measuring CI index,microstructure,malondialdehyde?MDA?content,ion permeability,the activities of phospholipase D?PLD?,lipoxidase?LOX?,polygalacturonase?PG?,pectin methyl esterase?PME?,superoxidase?SOD?,catalase?CAT?,phenylalanine ammonialyase?PAL?and glutathione s-transferase?GST?,the effect of GA deficiency on the cold tolerance of tomato fruit were determined.Based on transcriptomics and proteomics,the gene and protein level changes of WT and gib-3 tomato fruits stored at low temperature were compared,so as to further explore the role of GA on the chilling resistant of post-harvest tomato fruits.The main results are as follows.?1?Under low temperature storage,gib-3 tomato fruit showed more severe chilling symptoms and ultra-structural damage than WT tomato fruits.The MDA content,ion permeability and the activity of PLD,LOX,PG and PME of gib-3 tomato were increased.Cell membrane peroxidation and cell wall degradation of gib-3 tomato fruits accelerated,and their integrity of fruit cell membrane and cell wall was damaged.In addition,the activity of SOD,CAT,PAL and GST were decreased in gib-3 tomato fruits,and the ability of free radical scavenging reduced.?2?Transcriptome sequencing was performed on 0 and 14 day of gib-3 and WT tomato fruits under low temperature storage by RNA-Seq technology.Compared with WT,the GO function of gib-3 tomato fruit were significantly enriched in cellular processes,metabolic process,cell,organelle,binding and catalytic activity.The KEGG pathway were mainly enriched in galactose metabolism,starch and sucrose metabolism,fructose and mannose metabolism,carbon metabolism,glycolysis/gluconeogenesis.Six differentially expressed genes in response to cold stress were screened,and two of them were up-regulated which involved in the degradation of pectin in cell wall and 4 genes were down-regulated that involved in the starch and sucrose metabolism,fructose and mannose metabolism and metabolism of xenobiotics by cytochrome P450.?3?Proteome identification was performed on 0 and 14 day of gib-3 and WT tomato fruits under low temperature storage by iTRAQ technology.Compared with WT,the GO function of gib-3 tomato fruit were significantly enriched in cell process,localization,metabolic process,single-organism process,cell,membrane,organelle,binding and catalytic activity.The KEGG pathway were mainly enriched in endoplasmic reticulum protein processing,phenylalanine metabolism,phenylpropane biosynthesis,flavonoid metabolism and glutathione metabolism pathway.Fourteen differentially expressed proteins in response to cold stress were screened,and one of them was up-regulated that involved in glutathione metabolism,and 11 of them were down-regulated that involved in endoplasmic reticulum protein processing,glutathione metabolism and phenylalanine metabolism.