Expression Patterns Of Key Genes For ABA Biosynthesis During Camellia Sinensis Dormancy Release In Spring Season

Tea plant(Camellia sinensis(L.)O.Kuntze)is a perennial evergreen woody plant.During the growth of the tea plant,it will inevitably encounter by the unfavorable climatic conditions,such as low temperature and high temperature are the major concern.In order to get through unfavorable climatic conditions,tea plants will go to dormancy stage.The factors affecting the dormancy release mainly focus on the photoperiod and temperature,but there are differences in the dormancy release process in different climatic conditions.We believed that the photoperiod and temperature may affect dormancy release by growth regulating hormones.The most studied hormones are gibberellic acid(GA)and abscisic acid(ABA).Although the relationship between ABA and dormancy has been studied in tea plants,it has not explained the regulation mechanism of ABA during the process of dormancy release in spring season.In order to elucidate the basic mechanism of bud dormancy,this dissertation focuses on these issues and conducts relevant research.The main research results obtained are as follows:(1)In order to identify CsNCEDs from the CCD family,six CsNCEDs and two CsCCDs were obtained from the tea plants genome and their transcriptome database analysis,and they were analyzed of their biological information and classified.(2)The expression of CsNCEDs in different organs and under different stress conditions were detected by Real-time quantitative PCR.It was known that CsNCED6 was expressed in seeds,while other CsNCEDs were either slightly expressed or not expressed in seeds.Through different stress expressions,CsNCED1 and CsNCED3 play a major role.(3)ABA biosynthesis enzymes CsZEP2,CsXDH and CsAAO were extracted from genomic and transcriptome database,and their full length was cloned.The complete ORFs were 1410,834,and 4047 bp,encoding 470,278,and 1349 amino acids,respectively.(4)During the spring dormancy release of tea plant buds,two temperature gradients were simulated to release dormancy and we found that at 25 °C,both CsNCED3 and CsAAO showed a down-regulated expression in both cultivars,which may cause a decrease in ABA synthesis,thus releasing dormancy.During 15 °C temperature treatment,the enzyme genes related to ABA synthesis pathway basically showed the oppositeexpression trend in two cultivated.Wuniuzao and Shifocui almost germinate at the same time.It can be seen that in temperature treatment,two varieties CsNCED3 and CsAAO are likely to be candidate genes.A significant difference was observed 2 h after heat treatment of two tea plant cultivated varieties,CsNCED1 and CsNCED3 were significantly down-regulated.Wuniuzao buds break,but Shifocui did not germinate,because the level required for Shifocui to break the dormancy may not be reached.During the continuous exogenous GA and ABA treatment,CsZEP1,CsZEP2,CsNCED1 and CsNCED2 showed the same trend in two cultivars.However,in the Shifocui CsNCED3 was slight downregulated,while it was up-regulated in exogenous GA and ABA-treated Wuniuzao.Therefore,it is hypothesized that although exogenous GA or ABA has induced expression of CsNCED3,it is more strongly regulated by temperature.