Effect Of Exogenous Methanol On Photorespiration Pathway In Cotton

It was discovered that application of exogenous methanol(MeOH) could stimulate C3 plant growth, but little was known about its metabolic pathways when exogenous MeOH was applied in C3 plants. And some researchers put forward to MeOH can promote the plants growth was due to its can increase the plant photosynthesis and inhibited photorespiration pathway. There exist three photorespiratory pathways in the lower photosynthetic organisms, and two ways can generate the intermediate product- glyoxylate. One is the photorespiratory pathway of higher plants, and the other is glycerate pathway, that is to say glycolate can be converted to glyoxylate by glycolate dehydrogenase(GDH), and moreover, glyoxylate can also oxidate of CO2. According to the recent studies in our laboratory, even if glycolate oxidase(GO) activity was restrained, the content of glyoxylate was still on the rise. So we guess may be the methanol activated the plant GDH activity in chloroplast, thus we speculate: there are likely to be exist glycerate pathway in higher plants. To confirm this hypothesis, this study carried out the following work.In this study, we sprayed the concentration of 30% methanol solution to the cottons under field conditions and evaluated t the effects of(i) exogenous MeOH impact on several key enzyme activity of photorespiration;(ii) exogenous MeOH on photorespiratory major metabolites intermediates—glycolate and glyoxylate levels; and(iii) the possible photorespiratory metabolic pathways in cotton.The results showed that MeOH treatment significantly enhanced activity of Rubisco carboxylase and suppressed Rubisco oxygenase in 38.6% and 44.0%, respectively. Simultaneously, the exogenous MeOH as well inhibited GO activity(by 37.2% compared with the controls). It is very exciting, we also found that GDH activity in control and treatment cotton leaves and GDH activity increased 37.8% in MeOH-treated samples. The results can provide some evidences for the study of the possible metabolic pathways in MeOH-treated plants.