Effect Of Abscisic Acid Catabolic Genes On Dormancy Release In Tea Plants

As a kind of leafy woody plant,tea plant can improve the cold resistance ability through the dormancy of buds,and the early and late germination of tea buds affect the economic benefits.Therefore,it is necessary to study the mechanism of the dormancy and dormancy release of overwintering buds in tea plants.The study found that the premise of plant dormancy release is the rapid reduction of endogenous ABA content,but the molecular mechanism of this phenomenon is not clear.In this study,we cloned genes of ABA 8’-hydroxylase and β-glucosyltransferase by RACE method,and named them as CsCYP707A1a,CsCYP707A1b,CsCYP707A2,CsCYP707A3,CsCYP707A4 and CsAOG.The expression patterns of CsCYP707As and CsAOG in tea shoots,leaves,stems and root tissues were analyzed by qRT-PCR.We studied the expression of CsCYP707As under the temperature and the plant growth regulators in Wuniuzao and Shifocui.We analyzed the CsCYP707As response to GA/ABA,low temperature/high temperature and PEG treatment.These results provide new insights into the role of ABA in stress response,dormancy and germination of tea plants.The main research work and results completed are summarized as follows:1)Six key genes of ABA catabolism were cloned in tea plants.Among them,CsCYP707A1a and CsCYP707A1b have 7 exons,and CsCYP707A3 and CsCYP707A4 have 9 exons.The CsCYP707A proteins were located in the chloroplast.The CsAOG has no intron,the subcellular localization is in the cytoplasm.2)The amino acid sequence of CsCYP707As contains the highly conserved characteristic motif,and there is a membrane structure near the N-terminus of the sequence.The CsCYP707A genes were closely related to sweet orange,peach and grape.The CsAOG protein has a glucosyltransferase(UDPGT)conserved domain.There are 9 conserved elements in the CsAOG sequence.3)At 25℃,Wuiuzao breaks dormancy by about 10 days ahead of Shifocui.At 15℃,Wuiuzao and Shifocui broke dormancy after 26 days.Heat shock treatment is an effective way to break the dormancy of tea plants.GA treatment can promote the germination of tea seedlings,and ABA treatment can inhibit the germination of late budding Shifocui tea seedlings.4)The expression of CsCYP707Ala and CsCYP707A1b in roots was significantly higher than that in shoots,leaves and stems.CsCYP707A3 was significantly upregulated by exogenous GA and ABA.CsCYP707A1a was significantly up-regulated in response to low temperature(4℃),and CsCYP707A was significantly down-regulated by high temperature(38℃).CsCYP707As was induced by PEG,and its expression was up-regulated after rehydration.The CsAOG is mainly involved in the regulation of ABA content during early winter.