Danger-Associated Peptide Regulates Root Growth by Promoting Protons Extrusion in an AHA2-Dependent Manner in Arabidopsis

Plant elicitor peptides (Peps) are damage/danger-associated molecular patterns (DAMPs) that are derived from precursor proteins PROPEPs and perceived by a pair of leucine-rich repeat receptor-like kinases (LRR-RLKs), PEPR1 and PEPR2, to enhance innate immunity and to inhibit root growth in Arabidopsis thaliana. In this study, we show that Arabidopsis Pep1 inhibits the root growth by interfering with pH signaling, as acidic condition increased, but neutral and alkaline conditions decreased the Pep1 effect on inhibiting the root growth. The perception of Pep1 to PEPRs activated the plasma membrane-localized H+-ATPases (PM H+-ATPases) —the pump proton in plant cell—to extrude the protons into apoplast, and induced an overly acidic environment in apoplastic space, which further promoted the cell swelling in root apex and inhibited root growth. Furthermore, we revealed that pump proton AUTOINHIBITED H+-ATPase 2 (AHA2) physically interacted with PEPR2 and served downstream of the Pep1-PEPRs signaling pathway to regulate Pep1-induced protons extrusion and root growth inhibition. In conclusion, this study demonstrates a previously unrecognized signaling crosstalk between Pep1 and pH signaling to regulate root growth.