Genome-wide identification and expression analysis of the Bcl-2-associated athanogene (BAG) gene family in barley (Hordeum vulgare L.) under drought and heat stresses

Background Barley ( Hordeum vulgare L. ) is a diploid species belonging to the Poaceae family. Owing to its economic value and relative resistance to adverse environmental conditions, Barley is considered a suitable model plant for the identification and characterization of a wide range of gene families, including the Bcl-2-associated athanogene ( BAG ) family. The BAG gene family encodes highly conserved molecular cochaperone proteins that play crucial roles in a wide range of biological processes and in plant responses to diverse stresses. Results This study aimed to identify and investigate the evolutionary relationship, genomic organization, and comprehensive expression profiles of BAG genes in barley across different tissues under heat and drought stresses. Seven members of the BAG gene family were identified in the barley genome. All HvBAG proteins contain a conserved BAG domain, which interacts with calmodulin- and ubiquitin-binding domains located at the N-terminus. Phylogenetic analysis grouped the HvBAG proteins into three major clades (Group III). Analysis of cis-regulatory elements within the promoter regions of the HvBAG genes led to the identification of numerous motifs associated with plant development and stress responsiveness. qRT-PCR validation demonstrated distinct expression patterns of selected HvBAG genes under stress. For instance, HvBAG1 and HvBAG6 showed the highest expression levels in leaves, whereas HvBAG2 , HvBAG3 , and HvBAG4 were predominantly expressed in roots. Conclusions The observed differential expression between tissues under abiotic stress conditions indicates the involvement of distinct regulatory mechanisms governing HvBAG gene expression. These findings establish a foundation for future functional studies and genetic engineering efforts aimed at enhancing abiotic stress tolerance in crops.