Evolution of Bcl-2 Anthogenes (BAG) as the Regulators of Cell Death in Wild and Cultivated Oryza Species

Bcl-2-associated anthogenes (BAGs), chaperone regulators are known to regulate programmed cell death in plants. In the present study, we have identified eight BAG genes in the rice (Oryza sativa) genome. Subsequently, to understand the evolution, 78 BAG homologs were identified in other nine Oryza species. In addition to the signature ubiquitin-like domain, an additional conserved sequence of 12 amino acids was found in all the class I BAG genes except few exceptions in wild species. A significantly variable number of BAG genes was identified in different Oryza species indicates the expansion of BAG genes due to segmental duplication. Based on whole genome resequencing information available for 4726 rice genotypes, haplotype diversity and the functional effect of variations in BAG genes were predicted. Transcriptomic analyses further suggested the multifunctional roles of BAG genes during both developmental and defense response in Oryza species. Differential expression of BAG genes particularly BAG3 and BAG5 was observed under heavy metal stress. Similarly, higher expression of OsBAG1 and OsBAG2 were found in resistant rice cultivar in response to Magnaporthe oryzae infection and OsBAG2 showed upregulation in response to Xanthomonas oryzae infection as well. A similar expression of BAG genes was observed in the qRT-PCR analysis. Furthermore, heterologous transient expression of OInBAG6 protein tagged with yellow fluorescent protein in tobacco leaves showed the subcellular localization in both nucleus and plasma membrane. This study will help to understand the evolution of BAG genes and their role in cell death under stress conditions in rice.