Effects Of Low Temperature Stress On Physiology,biochemistry And Hormone Metabolism Related Genes Of Jiashi Melon

Jiashi melon is one of the varieties of cantaloupe in Xinjiang,and it is also a famous and special product and an important economic crop.Postharvest rot has always restricted the development of Xinjiang cantaloupe industry.Low-temperature storage can effectively slow down the rot of cantaloupe and extend its storage period.Phytohormones play an important role in regulating plant growth and development and resisting adversity.However,the relationship between hormone metabolism and storage characteristics and fruit quality in Jiashi melon has not been deeply studied.In order to elucidate the molecular mechanism of delaying the senescence of Jiashi melon fruits after harvest by inducing endogenous hormone metabolism and activating gene expression in response to low temperature stress and antioxidant system,Jiashi melon was taken as the research object,and the storage characteristics,physiological and biochemical characteristics,endogenous hormone metabolism and hormone signal transduction gene expression levels of Jiashi Melon under different storage temperatures were analyzed by using targeted metabonomics and transcriptomics analysis methods,and the correlation between storage characteristics,physiological indexes and plant hormone metabolism of Jiashi Melon under low temperature treatment was discussed.The main results are as follows:1.During the postharvest storage period of Jiashi melon,low temperature（3℃）significantly induced the increase of the activity of ascorbate peroxidase（APX）and superoxide dismutase（SOD）in Jiashi melon,inhibited the increase of polyphenol oxidase（PPO）and lipoxygenase（LOX）activities and slowed down the accumulation of malondialdehyde（MDA）and hydrogen peroxide（H₂O₂）.In addition,low temperature delayed the softening of Jiashi melon fruit,reduced the water loss caused by transpiration,slowed down the decline of soluble solid content（SSC）,maintained the nutritional quality of Jiashi melon,and reduced the decay rate.However,low temperature can not only maintain the quality of Hami melon,but also inevitably cause chilling injury to a certain extent.2.Targeted metabonomics analysis showed that low temperature significantly inhibited the increase of abscisic acid（ABA）content,and significantly promoted the accumulation of indoleacetic acid（IAA）and salicylic acid（SA）.Correlation analysis showed that ABA was positively correlated with H₂O₂ Content,MDA content,PPO enzyme activity,LOX enzyme activity,weight loss rate and decay rate,which indicated that ABA actively participated in the ripening and senescence of Jiashi melon.IAA was positively correlated with SOD activity and fruit firmness,and negatively correlated with ABA,which indicated that IAA and ABA had different regulatory mechanisms during the ripening and senescence of Jiashi melon.3.Transcriptome analysis shows that the expression levels of genes in the hormone signal transduction pathway under low temperature stress are significantly different.In the ABA signal transduction pathway,low temperature inhibits the level of ABA metabolism,and then induces the expression levels of PYL2,PYL12-like,PP2C 24,CPRF2-like,PYL9,RF2b,PP2C 16 and PYL8-like to significantly up-regulate and SAPK3-The expression of like,ABI5.6,ABI5.4,SRK2H-like,SRK2G-like,PYR1-like,MLP-like and ABCI12 were significantly down-regulated.In the IAA signal transduction pathway,low temperature promotes the accumulation of IAA content,which in turn induces IAA14,IAA16-like,IAA29-like,GH3.6-like,SAUR36 and ARF19-like genes in the auxin signal transduction pathway.The expression level was significantly increased.In the SA signal transduction pathway,low temperature induces a significant up-regulation of the expression levels of PRB1,TGA1,HBP-1b,NPR3-like and NPR5 family genes.The quantitative real-time polymerase chain reaction（RT-PCR）method was used to verify the expression levels of eight randomly selected genes.