Evolution of structural and functional diversification amongplant Argonautes

摘要

Argonautes (AGOs) are the effectorproteins of the RNA-induced silenc-ing (RISC) complex, formed during thephenomena of small-RNA mediatedpost-transcriptional gene silencing.AGOs are a large family of proteins; theirnumber varies from a few (4 inChlamy-domonas reinhardtii) to many (18 inOryza sativa) in plants. Genetics-guidedanalysis have demonstrated the roles ofsome of the AGOs during growth anddevelopment of plants. Biochemical stud-ies have further revealed differences infunctional specificities among AGOs.How the AGO family expanded in differ-ent plant species during the course ofevolution is starting to emerge. Wehypothesized that 4 classes of AGOsevolved after divergence of unicellulargreen algae when an ancestral AGOunderwent duplication events. Evolutionof multicellularity may have coincidedwith the diversification of AGOs. A com-parative sequence and structure analysisof the plant AGOs, including those fromthe mosses and the unicellular algae,show not only conformational differencesbetween those from lower and higherplants, but also functional divergence ofimportant sites.