Cell wall integrity and elicitor peptide signaling modulate jasmonic acid-mediated camalexin production in Arabidopsis.

Plant cell walls constitute dynamic barriers that are essential for defense against pathogens. Beyond a structural role in blocking pathogen infection, innate mechanisms monitor cell wall integrity (CWI) in Arabidopsis thaliana and trigger local responses where integrity is impaired. Here, we show that THESEUS1 (THE1)-dependent CWI signaling induces accumulation of the antimicrobial metabolite camalexin upon cell wall damage (CWD) caused by isoxaben (ISX)-induced cellulose biosynthesis inhibition or infection with the phytopathogenic fungus Colletotrichum higginsianum. CWD caused by ISX alters THE1 plasma membrane nanodomain organization and involves calcium signaling components that modulate camalexin production. Induction of camalexin requires jasmonic acid (JA) signaling and JA-dependent expression of the transcription factor MYB47. In line with its antagonistic function on CWI signaling, the plant elicitor peptide Pep3 suppresses camalexin biosynthesis downstream of THE1 by inhibiting JA-dependent pathways. Our findings reveal a regulatory network where CWI and Pep3 signaling modulate antimicrobial defense via JA-mediated camalexin production. This network requires input from independent CWD-induced pathways, providing insights into how plants balance distinct defense processes in response to cell wall stress.