Aluminum uptake and disease resistance in Nicotiana rustica leaves

The comparative effectiveness of aluminum hydroxide and aluminum chloride has been studied in the development of bacterial wilt infection on leaves of Nicotiana rustica cv. Gansu yellow flower. We have analyzed the changes of foliar H2O2 content, as well as of non-enzymatic and enzymatic antioxidants under aluminum stress. Pretreatment with aluminum hydroxide before pathogen challenge reduced the development of Ralstonia solanacearum infection and decreased the extent of leaf injury. The pretreatment also reduced the Al uptake in comparison to pretreatment with aluminum chloride. H2O2 generation was significantly enhanced by pretreatment with aluminum hydroxide. Increased NADPH oxidase and superoxide dismutase activities were correlated with limited infection. Aluminum hydroxide pretreatment shifted the leaf redox homeostasis of AsA/DHA and GSH/GSSG toward oxidation, yielding higher oxidant levels than aluminum chloride before bacterial inoculation. The results support the idea that aluminum hydroxide induced H2O2 accumulation through non-enzymatic and enzymatic regulation, ultimately resulting in resistance to tobacco wilt disease.