Analysis Of The Expression Characteristics Of Genes Related To Ethylene Biosynthesis And Signal Transduction Pathway During The Oriental Melon Fruits Ripening Affected By Grafting

Oriental melon(Cucumis melo var.makuwa Makino)is a typical climacteric fruit,and the fruit ripening is closely related to ethylene.Grafting is widely used as a cultivation technique to reduce and overcome the obstacles of continuous cropping,but grafting can also reduce fruit quality and delay fruit ripening.In this experiment,oriental melon 'Yinquan No.1' and white-seeded pumpkin 'Shengzhen No.1' were used as scions and rootstocks,respectively.The self-rooted and grafted oriental melon fruits of 28 DAA,31 DAA,33 DAA,35 DAA,37 DAA and 40 DAA were used as experimental materials.Firstly,ethylene production and enzymes related to biosynthesis pathway of self-rooted and grafted oriental melon fruits were determined by gas chromatography and enzyme-linked immunosorbent assay(ELISA),and the delayed ripening of grafted fruits was determined.Secondly,the expression of genes related to ethylene biosynthesis and signal transduction pathway was measured by quantitative Real-Time fluorescence quantification(q RT-PCR),and the main quality indicators of fruit were measured by liquid chromatography.Finally,the above indicators of grafted oriental melon fruits treated with ethephon during the color conversion period(25 DAA)were determined to explore whether the effects of grafting on ethylene production and gene expression of oriental melon fruits could be restored by exogenous ethylene.The purpose of this study was to explore the mechanism of grafting on ethylene biosynthesis and signal transduction pathway related gene expression during fruit ripening of oriental melon,and to provide theoretical and practical basis for further exploring the mechanism of grafted melon fruit ripening and quality regulating.The main results are as follows:1.The ethylene production of self-rooted oriental melon fruit reached the peak at 33 days after anthesis,while grafting delayed the peak ethylene production to 35 days after anthesis.Grafting mainly delays the peak of ACS activity,ACO activity and ACC content by delaying the peak of Cm ACS1 and Cm ACO1 gene expression,thus delaying the peak of ethylene production2.During fruit ripening of oriental melon,grafting delayed the peak expression of Cm ETR1 and Cm CTR1,significantly increased the expression of related genes Cm ETR1 and Cm ERF1,significantly decreased the expression of Cm ERF2.Grafting also significantly decreased the content of different sugars in oriental melon navel pulp,decreased the content of soluble solids in fruit,and increased fruit firmness.This indicated that grafting affected the gene expression pattern of ethylene signal transduction pathway and reduced the fruit quality of oriental melon in varying degrees.3.Ethephon treatment only increased ethylene production of grafted fruits at 28 and 31 days after anthesis,but did not reach a significant level,and did not advance the peak values of Cm ACO1 gene expression,ACS activity,ACC content,ACO activity and ethylene production.Ethephon treatment significantly increased the expression of Cm ACS1,Cm ACS2,Cm ACO1,Cm RIN3 and Cm RIN15 during grafted fruit ripening.The results showed that ethephon treatment did not advance the peak of ethylene production in grafted fruits,but significantly up-regulated the expression of related genes in ethylene biosynthesis pathway.4.Ethephon treatment mainly advanced the peak of Cm ETR1,Cm ERS1,Cm CTR1,Cm EIN3 and Cm EIL1 gene expression of grafted fruit,it significantly decreased the expression of Cm ETR2 gene and increased the expression of Cm EIN3 gene,accelerated fruit softening and formation of soluble solid,significantly decreased the content of different sugars in the middle pulp of grafted fruit.It can be seen that ethephon can affect the expression pattern of genes related to ethylene biosynthesis and signal transduction pathway in grafted fruit,but it does not advance the peak of ethylene production and does not improve the quality of grafted oriental melon fruit.Therefore,this experiment shows that the phenomenon of delayed fruit ripening and reduced fruit quality of grafting could not be restored by exogenous ethylene.