Heavy Metal-Associated Proteins in Plants: Genome-Wide Identification and Functional Insights from Angiosperms and Ancestral Plants.

Heavy metal-associated (HMA) proteins are mainly metal ion transporters and are involved in heavy metal homeostasis and detoxification processes. However, despite the importance of this protein family, their role in several plant species has not been identified nor studied. In the present work, a genome-wide identification methodology was used to identify HMA proteins in 13 plant species, in a representation of angiosperm species belonging to the clades of magnoliids, monocotyledons, and eudicotyledons, and non-angiosperms such as Physcomitrella patens and Selaginella moellendorffii. The identified proteins were analyzed for phylogenetic relationships, prediction of protein domains and motifs, physicochemical characteristics, gene structures, and cis-elements present in the promoters. We found that all plant species have HMA proteins, according to the analysis carried out, it allowed us to propose 5 HMA groups, each one with a different gene and protein structure. Among these subfamilies there are the copper chaperone for superoxide dismutase (CCS) and the P1B-ATPase groups. Furthermore, the cis-elements found in the promoters of these genes suggest mainly possible functions in abiotic stress scenarios, not only caused by the presence of heavy metals but also by the exposure to drought, salts, light, as well as by plant hormones, biotic stresses and developmental processes. Our results provide new knowledge about the possible HMA proteins that are present in Persea americana, Cinnamomum micranthum, and ancestral species such as S. moellendorffii and P. patens, and their possible characteristics and functions against phenomena like abiotic stress.