AbstractThe Bcl-2-associated athanogene (BAG) family is an evolutionarily conserved, multifunctional group of co-chaperones regulators that modulate a number of diverse processes. PlantBAGgenes were identified to play an extensive role in processes of programmed cell death (PCD) ranging from growth and development to stress responses. In this study, we identifiedBAGgenes from different photosynthetic organisms in order to gather evolutionary insights on these proteins followed by anin silicocharacterization of theBAGfamily in the bryophytePhyscomitrium patens. Ten putativePpBAGsharbouring a characteristic BAG domain were grouped into two subfamilies based on the presence of additional conserved domains and phylogenetic distances. Group I consisted of PpBAG4 and PpBAG5, containing an additional ubiquitin-like domain, and PpBAG10 with only the BAG domain. Group II consisted of PpBAG1–3 and PpBAG6-9, containing a calmodulin-binding IQ motif, a novel feature associated with plant BAG proteins. Interestingly, PpBAG9 exhibits an EF-Hand domain, not reported to date in this class of proteins. Caspase cleavage sites in PpBAG1, PpBAG3, PpBAG4-5 and PpBAG9 were predicted.In silicoanalysis ofBAGgenes revealed the presence of stress responsive elements, and a stress-regulated expression pattern which appears to be dependent on specifically organized promoter regulatory elements. According to our analyses, the present data suggest that some members ofP. patens BAGgene family may play a role in heat responses, autophagy and pathogen immunity. Further studies are required to unveil the role of specific members of this gene family in PCD and stress responses inP. patens.Key messageGenome-wide identification and phylogenetic relationships combined within silicogene-expression profiling and protein-interaction analysis of PpBAGs inPhyscomitrium patens, highlight the importance of a particular set in stress tolerance.