Changes Of Genes Expression In Cucumber Under High Temperature Stress (Cucumis Sativus. L)

Cucumber(Cucumis sativus L.,2n=2x=14)is an annual climbing herb of the Cucumis family of Cucurbitaceae.It is a kind of melon crop commonly cultivated in the world.What is more,It is one of the most widely grown major vegetable crops in China..With the global climate becoming warmer,high temperature damage has brought serious impact on the production of cucumbers,and it has become one of the problems encountered and urgently needed to be solved in cucumber production.The selection and breeding of cucumber heat-tolerant varieties focuses on traditional breeding methods,which takes time and effort,and it is difficult to achieve a high degree of polymerization of quality,yield,and heat resistance.However,there are few researches on the molecular mechanism of heat damage.The previous studies were mostly limited to the development of traditional molecular markers.There is still a lack of systematic and in-depth research on the localization of cucumber heat-resistant genes.In this study,based on the identification and screening of heat resistance of 80 cucumber germplasm resources,cucumber heat-tolerant strain 'GY2' was used as the test material.The differences in the level of whole genome transcriptomes of 6 h(T1)and 12 h(T2)at 43(±1)?were analyzed using RNA-seq technique.Selected candidate genes were tested for expression in the heat-tolerant strain ' GY2' and the high-temperature-sensitive strain 'Ping wang ru gua'.The main findings are as follows::(1)At the two time points,differentially expressed genes were analyzed and a total of 6063 differential genes were obtained.Among them,3196 genes were differentially expressed,1702 genes were up-regulated and 1494 were down-regulated when treated at 43 ? for 6h;4711 genes were differentially expressed,2038 were up-regulated,and 2673 were down-regulated at 12h.(2)Through the analysis of GO gene enrichment and KEGG pathway analysis,combined with functional annotation of cucumber genome database,it was shown that the genes responding to high temperature stress were mainly concentrated in the three major categories related to photosynthesis,heat shock transcription factors and heat shock proteins.A total of 18 heat-resistant candidate genes were finally identified.(3)Using qRT-PCR technology,we verified the heat-resistant candidate genes in the high-temperature strain ' GY2' and the high-temperature-sensitive strain ' Ping wang ru gua'.We obtained six genes that may be related to cucumber heat resistance.These include 2 heat shock transcription factor genes and 4 heat shock protein related genes.The expression of these six candidate genes in 'GY2' increased with the time of high temperature stress increasing,but no significant change was observed in 'Ping wang ru gua'.CsalG467710 was up-regulated in high-tolerance/sensitive strains and was expressed at different temperatures.The expression level of this gene in 'GY2' was significantly higher than that of 'Ping wang ru gua'.It is preliminarily believed that CsalG467710 plays an important role in cucumber response to high temperature stress.