The Research Of Cloning PSY Family Genes And Their Expressing Character In Watermelon

Watermelon(Citrullus lanatus L.)is a prefered vegetable or fruit in summer.It has important economic value and contains abundant carotenoid.Watermelon is deeply loved by people.Therefore,the research on the cloning and expression of the genes involved in the synthesis of carotenoids in watermelon has gradually become a hot topic.The research on the cloning and expression of the related genes of carotenoid synthesis will provide important theoretical basis for high quality breeding in watermelon.The first committed and rate-controlling step is mediated by nuclear-encoded phytoene synthase(PSY),which catalyzes the conversion of two molecules of geranylgeranyl pyrophosphate(GGPP)to phytoene.The expression level and enzyme activity of PSY affect the content of carotenoids in plants.Hence,phytoene synthase has the important value as a key enzyme in the carotenoid biosynthetic pathway.In this study,six watermelon accessions with different flesh colour were examined,white-fleshed ZXG0000;ZXG77 has pale-yellow flesh;ZXG55 and ZXG1594 have light-pink flesh;and ZXG1549and ZXG79 have red flesh.The expression level of flesh in six watermelon varieties from friuit setting to mature during the five development stages was tested by the technology of fluorescence quantitative PCR(qPCR).The expression patterns of three genes(PSY1,PSY2,PSY3)in different tissues were also analyzed through qPCR.It was measured through the high performance liquid chromatography to detect the protein actity of PSY_S.The main research contents and results are as follows:1.The expression of PSY1 was different in watermelon with different flesh color.The expression of PSY in white-fleshed ZXG0000 has the lowest expression.PSY2 and PSY3 expression level have little changes and much lower than the expression level of PSY1,It is speculated that PSY1 plays a major role in the metabolic pathway of carotenoids in watermelon fruit.2.PSY genes is expressed in different tissuess of watermelon.PSY1 plays a important role in watermelon fruit.PSY2 is detced in flowers,stems and leaves with a higher expression level than PSY1and PSY3,PSY3 has the highest expression level in the root.Although three transcripts were detected in all tissues,the differences in expression level showed that the PSY genes expression had tissue specificity.3.Successfully constructed the prokaryotic expression vectors of PSY1,PSY2 and PSY3,Using carotenoid engineering strain arrange function complement experiment,The proteins encoded by three genes were identified by high performance liquid chromatography.It turns out that PSY family genes have enzyme activity.