Foyer, Christine H., Garmier, Marie, Priault, Pierrick, Vidal, Guillaume, Driscoll, Simon, Djebbar, Reda, Boccara, Martine, Mathieu, Chantal, de Paepe, Rosine, University of Newcastle (UoN), Université Paris-Sud - Paris 11 (UP11), Ecologie et Ecophysiologie Forestières [devient SILVA en 2018] (EEF), Institut National de la Recherche Agronomique (INRA)-Université de Lorraine (UL), and Université Pierre et Marie Curie - Paris 6 (UPMC)
International audience; Light and oxygen are considered to be important in the execution of programmed cell death (PCD) in plants, principally because they are involved in the generation of reactive oxygen species (ROS). We compared the hypersensitive response (HR)-like PCD process in N. sylvestris leaves that is elicited by harpin Nea,, under light/dark and atmospheric/very low oxygen (VL ox: < 0,1%). PCD was induced under all conditions, but it was delayed in the dark and accelerated under VL ox. Rapid inhibition of photosynthesis and an acceleration of respiration are characteristic of light–elicited leaves. The harpin-induced collapse of CO2 assimilation and photosystem II activity was delayed under VL. Moreover, the burst of CO2 release caused by enhanced mitochondrial respiration in dark-elicited leaves was inhibited under VL ox. Superoxide and hydrogen peroxide accumulation inside the chloroplasts was observed in both the light and the dark, but not under VL ox. The accumulation of transcripts encoding cytosolic antioxidant genes was also greatly affected by oxygen deprivation. These results indicate that extra-mitochondrial ROS are not key signals to harpin-induced cell death. Rather, the acceleration of the HR-like process under VL ox is associated with the perturbation of respiratory pathways and possibly enhanced mitochondrial ROS production.