Genome-wide Identification Of The BASS Gene Family In Plant And Preliminary Functional Characterizations Of GhBASS2 Against Drought Stress

Drought and salt stress are important factors affecting plant growth.More importantly,these problems will directly affect the production of crops and have a great impact on agricultural production.It is of great significance to excavate the genes of drought and salt tolerance for the development of new crop varieties,also,for the utilization of dryland and saline-alkali land.Bile acid:Na~+sodium symporter(BASS)is a sodium-dependent transporter family found in fungi,bacteria,animals,plants and other organisms.The BASS proteins co-transports Na~+with pyruvate,glyoxylic acid,2-ketoacid and other small molecules,which are involved in stress response,photorespiration,plasma membrane repair and other processes of plants,and play an important role in the growth and development of plants,too.In this study,through the systematic identification and comprehensive analysis of the BASS gene family in 40 species of organisms.meanwhile,analysing of transcriptome data and the study of the drought-resistant function of Gh BASS2,conclusions were below:(1)In this study,BASS genes in 40 species were identified,and 6,8,15,and 17BASS genes were identified in Arabidopsis,Brassica rapa,Triticum aestivum,and Gossypium hirsutum,respectively,and they were divided into five subfamilies.Species evolution analysis showed that the BASS gene family expanded in the order of BASS?,BASS?,BASS?,BASS?,BASS?,Through the analysis of gene structure,protein conserved module sequence and protein transmembrane domain,each member of the BASS gene is relatively conservative in gene structure and protein structure,and the internal gene structure of each subfamily member is highly similar.All members of the BASS gene family retain two conserved Na~+binding sites and SBF domain.However,there are some differences in gene structure and protein structure between each subfamily.(2)Whole genome duplication event is the driving force for the evolution of the BASS gene family.With the occurrence of WGD,each subfamily of BASS has different degrees of expansion.In the evolutionary process,the Bass gene also maintains the characteristics of biased fractionation in some subfamilies,such as the BASS?subfamily of Nicotiana tabacum and the BASS?subfamily of Eutrema salsugineum,etc.In those species,the number of members of these subfamilies is obviously more than that of others.(3)Analysis of transcriptome data indicated that BASS gene plays an important role in the process of plant response to various abiotic stresses,and has a positive response to drought,salt,light and hormone stress.Transcriptome data of Arabidopsis thaliana,Oryza sativa,Triticum aestivum,Brassica rapa and cotton showed that the stress response patterns of BASS homologous genes were basically the same in different species,most of BASS genes are down-regulation trend in response to drought and salt stress,and up-regulation trend in response to light or heat treatment.(4)The transcriptome data also showed that the Bass?and the Bass?subfamilies had more positive responses to drought and salt stress than that in other subfamilies.In model organism Arabidopsis thaliana,Bass?subfamily has higher expression levels in roots,stems,leaves and other tissues than other subfamilies.(5)The cloning of AtBASS6 was completed,and plant expression vectors of At BASS6 gene was constructed,and then transformed into wild type Arabidopsis thaliana plants by Agrobacterium-mediated dipping inflorescence infection method.Overexpressed materials were obtained through resistance screening.What's more,T-DNA insertion mutants of Atbass1,Atbass3 and Atbass4 were obtained through PCR screening.A batch of complete BASS gene mutants and overexpression materials in Arabidopsis were obtained,combined with the overexpression materials previously created by our group.(6)Overexpression of GhBASS2 could improve drought tolerance of Arabidopsis thaliana.Under PEG-simulated drought stress,Arabidopsis thaliana with over-expression of Gh BASS2 had smaller stomatal aperture and significantly increased proline content and soluble sugar content in leaves compared with wild-type and mutant Arabidopsis thaliana.