Identification Of SnRK2 Gene Family In Tea Plant And Function Research Of CsSnRK2.5

Tea plant [Camellia sinensis(L.)O.Kuntze] is one of the most important economic crops originated from southwestern of China,Which prefers to grow in a humid,mild acidic environment.In recent years,extreme weather has occurred frequently,The environment of spring cold spells,persistent high temperature and drought has seriously affected the growth of tea plant and the quality of tea,which extremely restricts the production of tea.Therefore,cultivating new stress resistant varieties is one of the key objectives in current research of the tea plant.However,the mechanism research of stress resistance in tea plants is still insufficient,and the identification of stress resistance-related genes is still limited.The SnRK2 protein kinase is reported to be closely related to abiotic stress responses and ABA signal transduction in plants.Therefore,in this research,SnRK2 members in tea plants were identified at genome-wide level,and their expression patterns in tissue development,ABA signal and osmotic stress and the subcellular localization of their coding proteins was also analyzed.In addition,the function of CsSnRK2.5 under drought stress was preliminarily explored by overexpressed in Arabidopsis thaliana.The main contents of this study include the following aspects: Genome-wide identification of SnRK2 members in tea plants and systematic study on their genetic structure,evolutionary relationship and basic physicochemical properties and the conservation motif of their coding proteins.Analysed the expression pattern of the tea plant SnRK2 genes in tissue development,ABA signal and osmotic stress.Explored the subcellular localization of the tea plant SnRK2 protein kinases in onion epidermal cells.CsSnRK2.5,the homologous gene of Arabidopsis AtSnRK2.6 was cloned and over-expressed in Arabidopsis thaliana in order to explored it’s function under drought stress.The main results of this research are as follows:1.Eight SnRK2 genes,named CsSnRK2.1-CsSnRK2.8 were identified from the tea genome database.The analysis of gene structure showed that CsSnRK2 s had a conserved gene structure and all the members contained 9 exons,The CsSnRK2 s were divided into three groups according to the phylogenetic results.Physicochemical properties of CsSnRK2 proteins showed that their molecular weights were approximately 40 kDa and all them were hydrophilic proteins.2.CsSnRK2 s has different expression patterns in tissues.CsSnRK2.2 was found highly expressed in roots,CsSnRK2.5/6 were found highly expressed in stems,while,CsSnRK2.1/8 and CsSnRK2.3/4/7 were found highly expressed in leaves and flowers respectively.3.CsSnRK2 were induced by ABA,PEG and NaCl in varying degrees.Under ABA treatment,members of the all Group 3 and some members of the Group 2 were induced,this result consistent with the researches in other plants,while,differently,CsSnRK2.1,belong to Group 1,aslo induced by ABA.When suffer PEG stress,the expression of all CsSnRK2 were induced,among them,CsSnRK2.7 showed the strongest response.Under NaCl stress,the expression of CsSnRK2.7 and CsSnRK2.8 showed no significant changes,while other CsSnRK2 s were up-regulated.4.The subcellular localization of CsSnRK2 s were explored in onion epidermal cells by Agrobacterium-meditated transformation.The results showed that CsSnRK2.3 was mainly localized in the cytoplasm,however,the rest of the CsSnRK2 s were localized in both the cytoplasm and the nucleus.5.Overexpression of CsSnRK2.5 increased the drought resistance of wild type Arabidopsis thaliana which mainly reflected in the following aspects: When suffer drought,the wilting degree,ROS content and MDA content of transgenic Arabidopsis thaliana were lower than wild type.In addition,the results of water loss rate of detached leaves indicated that water retentiveness of transgenic plants were stronger than wild type.In summary,this research provide the theoretical rational for study of stress resistance genes by identified the SnRK2 genes in tea plant.meanwhile,the function of CsSnRK2.5 under drought stress was preliminarily explored,which provided a new perspective for exploring drought resistance mechanism of tea plant and helped to further clarify the drought resistance mechanism of tea plant.