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. RGFs and their receptor genes, RGIs, were investigated comprehensively using phylogenetic and genetic analyses. We identified 203 RGF genes from 24 plant species, representing a variety of land plant lineages. We found that the RGF genes originate from land plants and expand via multiple duplication events. The lineage-specific RGF duplicates are retained due to their regulatory divergence, while a majority of RGFs experienced strong purifying selection in most land plants. Functional analysis indicated that RGFs and their receptor genes, RGIs, isolated from liverwort, tomato, and maize possess similar biological functions with their counterparts from Arabidopsis in root development. RGFs and RGIs 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.
Highlights
To test whether this peptide family is originated from horizontal gene
Our results showed that tandem duplications were not found in some monocots, while several pairs of tandem duplication gene pairs were found in Arabidopsis, poplar, medicargo, and and tandem duplication of the RGF family genes in angiosperms
Our results indicated that roots treated with modified synthetic RGF peptides or plants overexpressing MpRGF1 and ZmRGF1 showed a significantly enlarged root apical meristem (RAM) compared with their controls
Summary
The development of a robust root system is one of the essential innovations during plant terrestrialization. During the early colonization of land, the development of a root system is a giant leap, enabling plants to anchor and uptake water and nutrients in the soil [2,3]. The first type is named vascular plants, which contain recognizable roots with an apical meristem and a root cap to protect the apex of the growing root [5]. Another type is non-vascular plants, such as mosses and liverworts, which contain rhizoids without root caps. The evolution of crucial genetic mechanisms underpinning the root formation and gravitropic response of land plants, mosses and liverworts, needs to be investigated
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