Nitric oxide and hydrogen peroxide in tomato resistance: Nitric oxide modulates hydrogen peroxide level in o-hydroxyethylorutin-induced resistance to Botrytis cinerea in tomato

Abstract

Nitric oxide (NO) has been postulated to be required, together with reactive oxygen species (ROS), for activation of disease resistance reactions of plants to infection with a pathogen or elicitor treatment. However, biochemical mechanisms by which ROS and NO participate in these reactions are still under intensive study and controversial debate. We previously demonstrated that o-hydroxyethylorutin when applied on tomato leaves ( Lycopersicon esculentum Mill. cv. “Perkoz”) restricted Botrytis cinerea infection development. In this research we investigated ROS and NO generation in tomato plants treated with o-hydroxyethylorutin, non-treated and infected ones. The NO content was enhanced or decreased in the studied plants by supplying them with NO generator—SNP or scavenger—cPTIO. NO detection was carried out using diaminofluorescein diacetate (DAF-DA) in conjunction with confocal laser scanning microscopy. The influence of elevated and decreased levels of NO on B. cinerea infection development and ROS generation was studied. The elevated NO concentration in tomato leaves strongly decreased hydrogen peroxide concentration without affecting other studied ROS (superoxide anion and hydroxyl radical) levels. H 2O 2 concentrations in NO-supplied leaves were low regardless of further treatment of tomato leaves with o-hydroxyethylorutin or inoculation with B. cinerea. The low H 2O 2 concentration coincided with quick and severe infection development in NO-supplied leaves. As activities of enzymes generating (SOD EC 1.15.1.1)) and removing (APX EC 1.11.1.11, CAT EC 1.11.1.6) H 2O 2 were unchanged in the studied plants, the decrease in H 2O 2 concentration was probably due to a direct NO-H 2O 2 interaction.