Conserved RGF1 peptide signaling regulates root meristem development through ROS in Arabidopsis and rice.

The root meristem is essential for stem cell maintenance and root development in plants. In Arabidopsis, Root meristem Growth Factor (RGF) peptides and their receptors regulate root meristem size through reactive oxygen species (ROS)-dependent signalling. RGF1-mediated ROS redistribution post-translationally stabilises the root meristem master regulator PLETHORA2 (PLT2). Although genomic studies suggest that RGF-receptor modules are evolutionarily conserved across land plants, their functional characterisation has remained largely limited to Arabidopsis. Here, we show that Oryza sativa RGF1-1 (OsRGF1-1) functions as a rice homologue of Arabidopsis RGF1 (AtRGF1). CRISPR/Cas9-generated Osrgf1-1 mutants exhibited shorter seminal roots, reduced root meristem size, and decreased superoxide (O2•-) accumulation, and EdU staining confirmed reduced cell proliferation in these mutants. The Osrgf1-1 mutants were sensitive to low concentrations of chemically synthesised mature OsRGF1-1 peptide, which restored seminal root growth and O2•- accumulation in the mutants but had no detectable effect on the wild type. Functional analyses using Arabidopsis rgfr receptor mutants further demonstrated that OsRGF1-1 is perceived through conserved RGF receptor machinery. Together, our findings provide the first functional evidence that the RGF1-receptor-ROS signalling module is evolutionarily conserved between dicots and monocots in the regulation of root meristem development.