Cloning and function analysis of BAG family genes in wheat

By analysing the cDNA microarray of the salt tolerant mutant of wheat RH8706-49 under salinity stress, our results showed an expressed sequence tag fragment and acquired an unknown gene (designated as TaBAG) with a BAG conserved domain through electronic cloning and RT-PCR technology. The gene was registered into GenBank (No. FJ599765). After homologous alignment analysis, electronic cloning, and amplifying with RT-PCR, the other gene with a BAG conserved domain, TaBAG2, was obtained and registered into GenBank (No. GU471210). Quantitative PCR analysis demonstrated that TaBAG2 expression was induced by saline and heat stress. TaBAG gene expression under salinity stress increased remarkably but showed an insignificant response to heat stress. The adversity stress detection results showed that Arabidopsis overexpressing TaBAG and TaBAG2 exhibited an obvious salt tolerance increase. Under heat stress, Arabidopsis overexpressing TaBAG2 showed increased heat tolerance; however, the heat tolerance of Arabidopsis overexpressing TaBAG did not vary significantly under heat stress. Subcellular localisation results demonstrated that TaBAGs were mainly located in the cytoplasm and the cell nucleus. We applied fluorescence complementation and yeast two-hybrid technique to prove that TaBAG2 can obviously bond with TaHsp70 and TaCaMs. After the respective mutation of aspartic acid (D) and arginine (R) at high conservation in BAG domain of TaBAG2, the bonding interaction between TaBAG2 and TaHsp70 disappeared, indicating that the two amino acids were the key loci for the interaction between TaBAG2 and TaHsp70. Heat tolerance detection results demonstrated that the heat tolerance of Arabidopsis overexpressing and cotransfected with TaBAG2 and TaHsp70 was much higher than that of Arabidopsis overexpressing TaBAG2 and Arabidopsis overexpressing TaHSP70. This finding implies that the synergistic use of TaBAG2 and TaHSP70 can improve heat tolerance of plants.