Plant elicitor peptide 2 regulates root hair growth in an auxin-dependent pathway

Abstract Background and Aims Plant elicitor peptides (Peps), which originate from their precursor proteins known as PROPEPs, play essential roles as signaling molecules that modulate both plant defense responses and developmental processes. Methods In this study, we investigated the role of PROPEP2 and its derived peptide Pep2, in regulating root hair development in Arabidopsis thaliana. Root hairs at different growth stages along the primary root and in distinct zones of the root tip were analyzed. We further examined the relationship between Pep2 and auxin signaling in regulating root hair growth. Key results Our findings indicate that loss of PROPEP2 function results in markedly decreased root hair number and elongation during the primary root development phase, whereas root hair formation during the embryonic root stage remains unaffected. Notably, exogenous Pep2 application rescued these defects and even induced root hair formation in non-hair-forming regions. We further demonstrated that Pep2 enhances root hair growth by stimulating localized auxin production in the root tip region. The mutants defective in auxin production (yuc1 yuc4 and wei8 tar1 tar2) failed to respond to Pep2. Furthermore, we identified the receptor-like kinases FERONIA (FER) and [Ca2+]cyt-associated protein kinase 1 (CAP1) as critical components of the Pep2 signaling pathway, with mutations in these genes impairing root hair growth and rendering plants unresponsive to Pep2. Conclusions These results uncover a previously uncharacterized interaction between Pep2 and auxin signaling components in the regulation of root hair development, offering additional insights into the molecular control of root morphology.