Effect Of LED Supplement On Soluble Sugar And Ethylene And Its Regulation Mechanism In Oriental Melon (Cucumis Melo Var.makuwa Makino) Fruit

Cucumis melo var.Makuwa Makino is a subspecies of Cucumis melons belonging to the Cucurbit family,which is native to China,Japan and North Korea.Its fruit is crispy in texture,juicy and sweet,and is popular among consumers due to its unique aroma.For most greenhouses in China,there are no cooling and warming conditions,but only rely on natural temperature and light conditions.Therefore,low temperature and weak light conditions are easy to occur in autumn and winter stubble cultivation conditions in protected horticulture,which will seriously affect the growth and development of plants,resulting in lower yield and lower fruit quality.In recent years,LED supplementary light has been widely used in vegetable cultivation in solar greenhouse.Therefore,in this experiment,thin-skinned muskmelon ’YMR’ was used as the experimental material.Plants growing in the field and fruits harvested at the early stage of ethylene release were treated with different light quality supplementing.Firstly,the effects of different supplementing light qualities on the release of soluble sugar and ethylene in field melon fruits and in vitro fruits were studied,and the light qualities that could improve melon fruit quality and ethylene synthesis were screened.The key genes of sugar and ethylene synthesis pathway significantly induced by light were screened by q RT-PCR.Secondly,the expression patterns of PIFS and HY5 gene family members in melon genome were analyzed to screen the transcription factors significantly regulated by light.Finally,one-hybrid technique and GUS activity analysis were used to investigate the molecular mechanism of the interaction between CmPIFs and the key genes of ethylene synthesis pathway to regulate the flavor and shape of melon fruit,in order to provide theoretical and practical basis for the light filling cultivation of melon in autumn and winter.The main research results are as follows:1.In this study,red light(R),blue light(B)and red and blue 6:1(RB 6:1)were applied to the growing muskmelon at 20 days after flowering,and samples were taken at 0,5,10,15 and 20 days after treatment.It was found that RB 6:1 supplementing light could significantly increase the sucrose content and sucrose phosphate synthase activity in melons at mature stage.The expression level of CmSPSs gene in melon fruits increased firstly and then decreased during fruit ripening.Three CmSPSs genes were identified by the research group,which were CmSPS1,CmSPS2 and CmSPS4,respectively.The expression levels of CmSPS1 and CmSPS2 were significantly up-regulated after the RB 6:1 supplementing light treatment.The activities of ACC oxidase and ACC synthase in melon fruits were increased after RB 6:1combined light treatment.The expression patterns of CmACOs and CmACSs in melon fruits were analyzed by q RT-PCR,and it was found that CmACO1,CmACS1 and CmACS11 were three key genes in ethylene synthesis induced by light significantly.The RB 6:1 compound light significantly increased the ethylene release of melon fruits,and the peak of ethylene release was advanced to promote fruit ripening.2.Through the thin skin melon between different organizations(root,leaf,stem,leaf,male and female flowers,5 days after anthesis)and different development period(5,10,15,20,25,30 and 35 days of anthesis)expression level are analyzed,found that the light signal transcription factor CmPIFs and CmHY5,CmHYH in melon each organization and each period were expressed,and CmPIF1 and CmHYH expressed in mature fruit is higher,CmPIF8 gene expression quantity in the world outside of the fruit have higher expression in the rest of the organization,in the fruit development period,The expression of CmPIF8 was gradually down-regulated,suggesting that CmPIF8 might be a negative regulatory factor in its growth and development.For red and blue of the fruit of fill light processing CmPIFs and CmHY5,CmHYH.CmPIFs expression pattern analysis and CmHY5,CmHYH are induced by light of different level,and CmPIF3,CmPIF4,CmPIF8 and CmHYH transcription factors that may affect the downstream gene transcription activity,thus further influence ethylene releasing and soluble sugar content in fruit ripening process of accumulation.3.Collect melon fruits at the early stage of ethylene release(30 days after anthesis)and supplement them with different light qualities(red light and blue light).It was found that red light treatment could significantly increase the content of soluble sugar and the release of ethylene in fruits.After red light treatment,the activities of sucrose phosphate synthase,ACC oxidase and ACC synthase,and the expressions of CmSPS1,CmACO1,CmACS1 and CmACS11 were significantly increased.The above results indicate that red light can improve fruit quality and promote fruit ripening,and it can reach the commercial ripening stage in 3days treatment.The analysis of the expression of CmPIFs in isolated fruits after red light treatment showed that the expression of CmPIF4 gene was significantly higher than that of the control,and the expression of CmPIF8 gene was significantly lower than that of the control and CmPIF1,showing the opposite trend.The analysis of CmHY5 and CmHYH in melon fruits treated with blue light showed that blue light could increase the CmHY5 transcription level,and the level was significant at 3,5 and 9 days of postharvest.CmHYH was significantly induced by blue light,and the expression level of CmHYH was higher than that of the control at all stages.5.Through the analysis of elements on the CmACO1 promoter,it is found that there are G-box elements on the CmACO1 promoter that can bind to CmPIFS.In order to further explore how CmPIFs regulate CmACO1,yeast single hybridization test and GUS reporter gene test were used to demonstrate that CmPIF4 and CmPIF8 directly regulate the transcription of CmACO1,and CmPIF4 positively regulates the transcription activity of CmACO1,while CmPIF8 negatively regulates the transcription activity of CmACO1.In conclusion,red and blue 6:1 light supplementation can effectively increase the soluble sugar content and ethylene release of fruits.Supplementation of red light 3 days could make the muskmelon harvested in advance reach the commercial maturity stage.CmPIF4 directly and negatively regulates the expression of CmACO1 to promote ethylene production,while CmPIF8 directly and negatively regulates the expression of CmACO1 to inhibit ethylene production.Red light promotes ethylene production through the above pathways.