<i>WRKY30</i> negatively regulates lateral root development downstream of the RGF1–RGI1 peptide-receptor module in Arabidopsis

Small signaling peptides play pivotal roles in coordinating plant growth, development, and immunity. In Arabidopsis, ROOT MERISTEM GROWTH FACTOR 1 (RGF1) and its cognate receptor RGF1 INSENSITIVE 1 (RGI1) suppress lateral root (LR) development by activating the transcription factor PUCHI via mitogen-activated protein kinase signaling. WRKY30 has previously been identified as an early gene strongly induced by RGF1; however, its role in LR regulation remains unclear. Here, we demonstrate that WRKY30 functions downstream of the RGF1-RGI1 module to inhibit LR development. In ProWRKY30:GUS and ProWRKY30:SVnlsTomato lines, RGF1 treatment strongly induced reporter expression in the distal region of primary roots, while this response was markedly reduced in the rgi1 mutant. Furthermore, RGF1 enhanced WRKY30 promoter-fused GUS activity during LR development. Overexpression of WRKY30 under the UBIQUITIN10 or RGI1 promoters suppressed LR initiation in wild-type and rgi1 plants without affecting RGF1-promoted root meristem activity. Conversely, CRISPR-Cas9-generated wrky30 mutants exhibited reduced sensitivity to RGF1-mediated suppression of LR formation. Collectively, these findings indicate WRKY30 as a key downstream component of RGF1-RGI signaling that specifically restricts LR development.