Limited Zn Supply Affects Nutrient Distribution, Carbon Metabolism and Causes Nitro-Oxidative Stress in Sensitive Brassica Napus

Despite being a worldwide problem, responses of crops to zinc (Zn) deficiency is largely unknown. This study examines the effects of limited Zn supply in Brassica napus. The decreased Zn content of the nutrient solution caused reduced tissue Zn concentrations and reduced K, Ca, Mg levels were detected in the leaves. For Ca, Zn, Fe, Mo inhomogeneous distribution was induced by Zn limitation. Suboptimal Zn supply decreased the shoot and root biomass and altered the root structure. The levels of sugars and sugar phosphates (e.g. glucose, glucose-6-phosphate etc.) were decreased suggesting disturbance in carbon metabolism. Limited Zn availability induced organ-dependent superoxide anion and hydrogen peroxide production and triggered altered NADPH oxidase, superoxide dismutase activities, ascorbate peroxidase abundance and ascorbate and glutathione contents indicating oxidative stress. Moreover, nitric oxide, peroxynitrite and S-nitrosoglutathione (GSNO) levels and GSNO reductase gene expression, protein level and activity were modified by Zn limitation. As a consequence, protein tyrosine nitration and protein carbonylation were intensified in B. napus grown with suboptimal Zn supply. Collectively, these results provide the first evidence for Zn deficiency-induced imbalances in nutrient status, sugar contents, reactive oxygen and nitrogen species metabolisms and for the secondary nitro-oxidative stress in sensitive Brassica napus.