Ethylene Signaling Causing Tolerance of Arabidopsis thaliana Roots to Low pH Stress is Linked to Class III Peroxidase Activity
Résumé
One irreversible consequence of acidic pH for roots is cell death. Growing evidence suggests the role of hormones and cell wall-related enzymes in response to acidic pH that could possibly avoid cell mortality. Here, we have investigated the role of ethylene and class III peroxidases (CIII Prxs) activity on sensitivity to further low pH treatment. Seedlings of Arabidopsis thaliana were pretreated with ethylene, at various concentrations for various times, and then exposed to low pH. In contrast to non-treated roots, roots pretreated with ethylene for 3 h became tolerant to subsequent low pH, with negligible cell mortality in meristematic (MZ), transition (TZ), and early elongation (EZ) zones. This effect of ethylene was time dependent since it was achieved only when seedlings were pre-incubated with ethylene for at least 3 h. This tolerance induced by ethylene was not observed in the gain-of-function mutation etr1-1 (insensitive to ethylene 1–1). Besides, it was prevented by salicylhydroxamic acid (SHAM) which is an inhibitor of CIII Prxs activity. In late EZ, the decrease in cell expansion due to low pH was dependent on both ethylene signaling and a SHAM-sensitive process. The responses mediated by ethylene signaling might involve CIII Prxs-dependent cell wall modifications, leading to tolerance to low pH and arrest in cell expansion during stress.