Evolution of RGF/GLV/CLEL Peptide Hormones and Their Roles in Land Plant Growth and Regulation

Abstract

Rooting is a key innovation during plant terrestrialization. RGFs/GLVs/CLELs are a family of secreted peptides, playing key roles in root stem cell niche maintenance and pattern formation. The origin of this peptide family is not well characterized. <i>RGFs</i> and their receptor genes, <i>RGIs</i>, were investigated comprehensively using phylogenetic and genetic analyses. We identified 203 <i>RGF</i> genes from 24 plant species, representing a variety of land plant lineages. We found that the <i>RGF</i> genes originate from land plants and expand via multiple duplication events. The lineage-specific <i>RGF</i> duplicates are retained due to their regulatory divergence, while a majority of <i>RGFs</i> experienced strong purifying selection in most land plants. Functional analysis indicated that <i>RGFs</i> and their receptor genes, <i>RGIs</i>, isolated from liverwort, tomato, and maize possess similar biological functions with their counterparts from Arabidopsis in root development. <i>RGFs</i> and <i>RGIs</i> are likely coevolved in land plants. Our studies shed light on the origin and functional conservation of this important peptide family in plant root development.