Nitric oxid is involved in oxidative stress during rehydration of Ramalina farinacea (L.) Ach. in the presence of the oxidative air pollutant cumene hydroperoxide

[EN] Air pollution has dramatically decreased lichen diversity in polluted areas. However, the causes underlying this sensitivity are poorly known, hindering the prevention of biodiversity loss. Nitric oxide (NO) is a bioactive gas involved in stress signalling and free radical (ROS) defence, in addition to playing a role in complex atmospheric pollution chemistry. NO production in lichens during their rehydration was recently demonstrated. The aim of this study was to analyze the role of NO in the lichen Ramalina farinacea during rehydration in the presence of the oxidative air pollutant cumene hydroperoxide. To this end, ROS were visualized in vivo using the fluorescent probe DCFH2-DA, NO action was specifically inhibited with c-PTIO, and lipid peroxidation during rehydration in the absence or presence of cumene hydroperoxide was quantified. The results indicated that cumene hydroperoxide causes an increase in the release of intracellular free radicals within the fungal hyphae, together with lipid peroxidation of the whole lichen. Lipid peroxidation, but not oxidative stress reverted to physiological values after NO inhibition. We conclude that, in lichens, NO may be involved in the regulation of the oxidative stress caused by air pollution.