Influence of the high infectious load of the causal agent of bacterial ring rot of potatoes on variations in hydrogen peroxide and cAMP levels in transgenic potato plants <i>in vitro</i> with increased contents of endogenous hydrogen peroxide

Abstract

Effects of the infectious load of the causal agent Clavibacter michiganensis sps. Sepedonicus (Cms) of ring rot of potatoes on hydrogen peroxide and cAMP levels in potato plants in vitro were studied on three transgenic lines of the Scarb cultivar: line L17.2 – plants transformed with the native gene of glucose oxidase gox from the highly active fungal strain Penicillium funiculosum 46.1; line M7.3 – plants transformed with the modified gene gox-mod; and line Pb14.10 – plants transformed with a vector without a target gene. In addition, non-transgenic plants of the same cultivar (medium resistant against Cms), Lugovskaya (resistant against Cms) and Lukyanovsky (susceptible to Cms) were examined. In the plants infected with Cms (0.2х10 8 cells/ml), the dynamics of cAMP and Н2О2 indicated a balanced system signal “root–stem”. The Cms titre (2х10 8 cells/ml) caused a systemic increase in the concentration of Н 2 О 2 in the organs of almost all plant cultivars; however, a systemic increase in the level of cAMP occurred only in the Lugovskaya cultivar. In all the studied transgenic lines, cAMP levels remained at the control level, accompanied by both local and extensive necrosis. In transgenic potato lines, the observed decrease in protective responses (both local and extensive necrosis) is likely to be associated with an extremely high baseline level of endogenous hydrogen peroxide and an imbalance in cAMP levels. The introduction of the gox gene into potato plants was found to increase their resistance against high Cms titres.