Genome-wide identification and molecular evolution analysis of BPA genes in green plants

Reactive oxygen species (ROS) signaling plays a central role in plant immune response. BPAs, referred to as binding partner 1 of accelerated cell death 11 (ACD11) (BPA1) and BPA1-like proteins, regulate ROS-mediated defense responses in Arabidopsis thaliana. However, their distribution and evolutionary characteristics in the plant lineage remain unexplored. In this study, we demonstrated that most BPA genes form a plant-specific family with expansion events observed. We found that BPA and ACD11 genes co-exist in all land plants, suggesting that this immune regulatory module may originate at the early stage of land plant emergence and contribute to their colonization. Angiosperm BPAs can be classified into four distinct groups (I-IV) in our analysis. Domain organization and motif composition are highly conserved within each group but divergent across different groups. In certain species, BPAs undergo complex alternative splicing, suggesting their regulatory and functional divergence. The protein-protein interaction network we constructed predicted additional acting partners of BPAs. The yeast two-hybrid assay revealed 15 BPA interaction pairs forming homo- or hetero-dimers. Taken together, our results provide the first synopsis of BPA evolutionary pattern and adaptations to green plant colonization.