Regulation Of Tobacco GLDH Gene Transcription And Influences Of Ascorbic Acid And Glutathione On TMV Infection To Nn Genotype Tobacco

Ascorbic acid (AsA) has been found to play important roles in many physiological processes of higher plants including resistance to abiotic stresses and pathogen attack. In plants AsA is biosynthesized in mitochondria with the last step (L-galactono-γ-lactone→AsA) catalyzed by L-galactono-γ-lactone dehydrogenase (GLDH, EC 1.3.2.3). Some refernces reported that AsA biosynthesis in plants could be modulated by mitochondrial respiratory chains. But the deep modulating mechanisms are still not quite clear. Some previous work in our laboratory found that high temperature stress could affect that AsA biosynthesis activity of plant cells. But the mechanism of this influence is still unclear. Furthermore, it is still unknown whether the reductants such as AsA can influence the infection of virus to susceptible plants. Therefore, this thesis is aimed at studying the effects of mitochondrial respiratory chains and high temperature stress on GLDH gene expression in tobacco cells, and the influence of reductants such as AsA and GSH on the infection of TMV to tobacco (Samsun, nn). The following results have been obtained:1) When suspension-cultured tobacco cells was treated with SHAM or NaN₃ alone, the transcription of GLDH gene was suppressed at some extent. When SHAM and NaN₃ were used together, the suppression was even stronger than when the respiration inhibitors were used alone.2) High temperature stress (40°C) could also suppress the transcription of GLDH gene in suspension-cultured tobacco cells at some extent.3) Treatment with exogenous AsA or GSH showed influences on the infection of TMV to tobacco plants (Samsun, nn). But their influences depended on the concentrations of AsA, GSH, and their solvents. Generally speaking, AsA suppressed the infection of TMV at some extent, but GSH promoted the infection of TMV at some extent.