Analysis Of Chromogenic Components And Metabolism Related Genes In Stigma Of Melon

Melon [Cucumis melo L.(2n=2×=24)] belongs to Cucurbitaceae,which is rich in a variety of essential minerals(calcium,phosphorus,iron,etc.)and vitamins(carotene,thiamine,riboflavin,nicotinic acid,vitamin C,etc.).And it is one of the most popular fruits among consumers and one of the top ten fruit vegetables in the world.Recently,with the continuous expansion and upgrading of planting area and industrial scale,melon breeding had become particularly important.Melon belongs to the economic crop of alienation pollination,and stigma plays an important role in pollination and reproductive development of melon.In nature,the stigma of melon is mainly green and yellow,while its petals and pollen are mainly yellow.In the pollination seed production and fruit production of melon,the color difference between the green stigma and the yellow pollen is large,which makes it easy to observe whether the female flower stigma is pollinated and the degree of uniformity of pollination;in addition,the green stigma and the corolla form a sharp contrast,which can form an obvious pollen recognition area in the sight of most pollinators sensitive to the UV light area,which is easier to induce pollinators such as insects to land accurately on the stigma to complete the pollination process,further accelerate the pollination process,improve seed production efficiency and seed purity,and reduce the cost of hybrid seed production.Therefore,it is very important to analyze the main pigment components of yellow and green stigma of melon and to study its anabolic pathway and related gene expression,which will provide a good theoretical basis and practical basis for the selection of new varieties of melon.In this study,two green stigma melon strains(MR-1 and X100)and two yellow stigma melon strains(M4-7 and X193)were used as experimental materials.And we observed respectively the changes of color in different periods of stigma development,determined the content of chlorophyll and carotenoids in different development periods,and sequenced the transcriptome of green stigma material MR-1 and yellow stigma material M4-7.The main results are as follows:(1)The initial color of the stigma of the two types of melon material was green.When the female flower bloomed,the color of the green stigma material was green,while the color of the yellow stigma material was yellow.The period of color transformation in the yellow stigma was determined by field experiment.(2)Through the determination of the pigments content in stigma and data analysis,the chlorophyll content in the stigma of the green stigma strain was significantly higher than that of carotenoids and the color of stigma was green;the chlorophyll content in the stigma of the yellow stigma strain was significantly higher than that of carotenoids at the early stage of female flower development,but when the female flower bloomed,the carotenoid content was higher than the chlorophyll content,which lead to that the stigma color gradually changed from green to yellow.(3)By analyzing the transcriptome data of MR-1 and M4-7,combining with the gene function annotation and enrichment results of GO and KEGG pathway,11 genes were screened involved in chlorophyll synthesis,4 genes involved in chlorophyll degradation and 2 genes involved in carotenoid synthesis.The expression of 11 genes involved in chlorophyll synthesis in MR-1 at three stages was significantly higher than that in M4-7,and the expression of 4 genes involved in chlorophyll degradation was significantly lower than that in M4-7;the expression of 2 genes involved in carotenoid synthesis in MR-1 was significantly higher than that in M4-7.Therefore,we could speculate that the color of melon stigma showed yellow or green because of different expression patterns of DEGs.(4)The expression levels of 5 DEGs were verified by real-time quantitative PCR.Same results were gotten between quantitative results and transcriptome data in MR-1 and M4-7,indicating that the transcriptome data were reliable.The expression patterns of these 5 genes were the same in two green stigma materials,in the meantime same in two yellow stigma materials meanwhile.