Abstract
Since plants cannot move to avoid stress, they have sophisticated acclimation mechanisms against various stress factors. The phytohormone abscisic acid (ABA) plays essential roles in such stress tolerances in land plants. Therefore, it is interesting to address the evolutionary origins of ABA metabolism and signaling pathways in land plants. Here, we focused on 48 Arabidopsis thaliana genes with ten key functions (ABA-related genes), and generated ten orthologous clusters of ABA-related genes from A. thaliana, Arabidopsis lyrata, Populus trichocarpa, Oryza sativa, Selaginella moellendorffii, and Physcomitrella patens. Phylogenetic analyses suggested that the common ancestor of these six species had most of the key functions of ABA-related genes. In the lineage of A. thaliana, gene expansion of ABA-related genes led to the expression divergences. This result indicates that in the evolution of A. thaliana, ABA-related genes have their functions in distinct organs and in response to various environmental cues. Taken together, these results suggest that the expansion of ABA-related genes may have contributed to the sophisticated stress tolerance mechanisms of higher land plants.
