Abstract
BACKGROUND: Caleosins are lipid-associated proteins that exist in plants and fungi. Its molecules and biological functions have been extensively characterized, particularly in some economic crops. Different caleosins have various physiological roles in plant growth, development, and plant-environment interactions. However, a comprehensive investigation into their evolutionary history and patterns has yet to be undertaken. RESULTS: Here, we identified 922 caleosins from 203 species comprising green algae and other plant taxa, followed by large-scale phylogenetic analysis. Phylogenetic analysis indicates that the plant caleosin family gave rise to the H and L branches after the emergence of aquatic algae and before the appearance of land plants. Hornworts and liverworts lost the L-caleosin during the evolutionary process. Caleosins from Araucariaceae, Podocarpaceae, Sciadopityaceae, and Stangeriaceae are absent in the H clade, and those from Ginkgoaceae, Gnetaceae, Pinaceae, and Zamiaceae are missing in the L clade. This suggests that the H and L clades were lost at the family level. In addition, we present a more comprehensive phylogenetic structure of angiosperm caleosin. The H and L branches of angiosperm caleosin expanded once each, generating two branches, respectively. We also explored the diversification of caleosin in Brassicaceae and Poaceae, respectively. CONCLUSION: Our study offers a comprehensive understanding of the evolutionary trajectory of the caleosin gene family in green plants at a genome-wide level. These findings establish a crucial groundwork for future research to conduct thorough functional characterization.