Botrytis cinerea induces local hypoxia in Arabidopsis leaves.

Low oxygen availability is often associated with soil waterlogging or submergence, but may occur also as hypoxic niches in otherwise aerobic tissues. Experimental evidences assign a role in Botrytis cinerea resistance to a group of oxygen-unstable Ethylene Response Factors (ERF-VII). Given that infection by B. cinerea often occurs in aerobic organs such as leaves, where ERF-VII stability should be compromised, we explored the possibility of local leaf hypoxia at the site of infection. We analysed the expression of hypoxia-responsive genes in infected leaves. Confocal microscopy was utilized to verify the localization of the ERF-VII protein RAP2.12. Oxygen level was measured to evaluate the availability of oxygen. We discovered that infection by B. cinerea induces increased respiration, leading to a drastic drop in the oxygen level in an otherwise fully aerobic leaf. The establishment of a local hypoxic area results in stabilization and nuclear relocalization of RAP2.12. The possible role of defence elicitors, ABA, and ethylene was evaluated. Local hypoxia at the site of B. cinerea infection allows the stabilization of ERF-VII proteins. Hypoxia at the site of pathogen infection generates a nearly oxygen-free environment that may affect the stability of other N-degron-regulated proteins as well as the metabolism of elicitors.