Hydrogen peroxide-induced salt tolerance in the <Emphasis Type="Italic">Arabidopsis</Emphasis> salicylate-deficient transformants <Emphasis Type="Italic">NahG</Emphasis>

The effect of hydrogen peroxide treatment on the salt tolerance of wild-type Arabidopsis thaliana L. plants (Col-0) and plants transformed with the bacterial salicylate hydroxylase gene (NahG) was studied. The base tolerance to salt stress caused by 200 mM of NaCl in solution culture was higher in plants with the NahG genotype in comparison with the wild-type plants. Growth inhibition was observed for wild-type plants under the action of exogenous hydrogen peroxide, which was not observed for the NahG transformants; salt tolerance increased in the both types of plants after treatment, which was assessed based on the growth indicators and the ability to preserve the chlorophyll pool following NaCl treatment. The content of endogenous Н2О2 in the leaves of wild-type plants increased significantly following exogenous hydrogen peroxide treatment and salt stress, while it practically did not change in the leaves of the NahG genotype. The SOD activity increased in both genotypes after treatment with exogenous hydrogen peroxide, and remained at an elevated level after salt stress in comparison with the nontreated plants. Furthermore, the catalase activity increased in leaves of the salicylate-deficient genotype but not in the Col-0 genotype. The guaiacol peroxidase activity increased in plants of both genotypes under the action of hydrogen peroxide and salt stress, with the NahG plants demonstrating a higher degree of increase. The Н₂О₂ treatment facilitated the increase of the proline content in leaves of the plants of both genotypes under conditions of salt stress. It was concluded that there were hydrogen peroxide signal transduction pathways in Arabidopsis plants that were salicylic acid independent and that the antioxidant system functioned more effectively in salicylate-deficient Arabidopsis plants.