Identification,Evolution And Expression Analysis Of The KEA And NHX Gene Families In Arabidopsis Pumila

Ephemeral plants mainly distribute in arid desert areas,which use snowmelt and rainfall in early spring to rapidly complete their life cycle.The coverage of ephemeral plants is of great significance to the stability of sandy land surface,and play important roles in protecting surrounding farmland from sand damage.Arabidopsis pumila grows in northern Xinjiang that characterized with salt and alkali,drought and low temperature tolerances.The mining of genes related to stress resistance in A.pumila can provide ideas for the study of plant stress resistanceThe cation/proton antiporter(CPA)gene family plays cruical roles in plant growth and signal transduction by mediating the inverse transmembrane transport of cation(Na~+,K~+)and proton(H~+)to regulate intracellular ion and p H homeostasis.In this study,a detailed bioinformatics analysis was performed on five Brassicaceae KEA(K~+efflux antiporter)and A.pumila NHX(Na~+/H~+antiporter)families using genomic data,including gene identification,phylogenetic analysis,gene structure,motif prediction,and collinear analysis.The expression profiles of Ap NHX and Ap KEA genes under abiotic stresses were analyzed using q RT-PCR.The main research contents and results of this thesis are as follows:1.Genome-wide identification and comparative evolutionary analysis of the KEA gene family in A.pumila and four Brassicaceae plant species(1)Genome-wide sureveries identified 6,6,12,18 and 6 members of KEA family(K~+/H~+exchanger conserved domain)from Arabidopsis thaliana,A.lyrata,A.pumila,Camelina sativa and Eutrema salsugineum,respectively.(2)Phylogenetic evolution,gene structure,and motif analyses showed that 48KEA genes were divided into two subfamilies.However,the Trk A-N domains only existed in the members of Clade I.(3)Collinearity analysis demonstrated that the KEA family members have experienced both whole-genome duplication and segmental duplication events during the evolution of A.pumila and C.sativa,while most of the KEA members in A.thaliana,A.lyrata and E.salsugineum experienced mainly dispersed duplication events.(4)The collinearity of KEA genes among species indicated a complex evolutionary relationship between Brassicaceae species.2.The characteristics and expression analysis of KEA gene fmily in A.pumila(1)Multiple sequence alignment of 12 Ap KEA proteins revealed a Rossman fold conserved motif in Trka-N conserved domain of Clade I member.(2)The expression of A.pumila KEA genes significantly responded to high salt stress(250 m M Na Cl).In addition,the expression patterns of Ap KEA2.1/2.2 and Ap KEA6.1/6.2 were significantly different,suggesting that the functions of the duplicated genes were diverged.(3)q RT-PCR analysis showed that the expression of Ap KEA1.1,Ap KEA1.2,Ap KEA3.1 and Ap KEA3.2 genes played key roles in different K~+stress,and the majority of Ap KEA,were significantly induced under drought stress(15%PEG 6000),oxidation stress(1 mol/L MV)and hormone stress(1 mol/L ABA).(4)The analysis of transcript levels using RNA-seq data in different developmental stages and different tissues indicated that Ap KEA genes played important roles in the growth and development in A.pumila.3.Identification,evolution,and expression analysis of NHX gene family in A.pumila(1)A total of 15 Ap NHX genes were identified in A.pumila using genome-wide identification,and phylogenetic analysis showed that Ap NHX could be divided into three subfamilies:Vac-class,Endo-class and PM-class.(2)Motif analysis showed that the conserved amiloride binding site(LFFIYLLPPI)only presented in Vac-class proteins.(3)There were 13 pairs of collinearity genes in A.pumila,and the calculation of Ka/Ks values revealed that they experienced purification selection during revolution.(4)15Ap NHX genes underwent WGD/S duplication events.(5)RNA-seq analysis showed that Ap NHX genes possessed specific expression patterns in different tissues and developmental stages.(6)q RT-PCR analysis showed that most of the Ap NHX genes responded to drought,oxidation,and hormonal stress.In summary,a total of 48 KEA genes were identified in the genomes of five Brassicaceae plants and 15NHX genes were identified in the genomes of A.pumila.Genome-wide duplication/segmental duplication contributed the expansion of Ap KEA,Cs KEA,and Ap NHX gene families.Purification selections were the main force affecting KEA and NHX family genes.The gene expression analysis indicated that these genes played an important role in the growth and development of A.pumila and in response to different stresses.These results have deepened our new understanding of Na~+(K~+)/H~+antiporter in plants,and provided genetic resources and theoretical basis for further study of Na~+(K~+)/H~+equilibrium mechanism.