Research Of Exogenous Methanol On Mechanism Of Inhibition Photorespiration In Cotton

It was discovered that application of exogenous methanol (MeOH) in arid environment increases the C3plant yield in the early last century. Although reports on MeOH production, emission and its catabolismhave been documented in higher plants, and it is believed that MeOH alleviates CO2deficiency and inhibitsphotorespiration, little is known about its physiological role in plant growth and its relationship with thephotorespiratory intermediates when exogenous MeOH is applied in C3plants. It is well known thatphotorespiration is an essential auxiliary metabolic pathway that allows photosynthesis to happen inoxygen-containing environment in terrestrial C3plants. It occurs because oxygen can substitute carbondioxide in the first reaction of the photosynthetic carbon dioxide-fixation process and arrests the synthesisof2-phosphoglycolate (2-PG) in chloroplast. Therefore,2-PG is considered as a byproduct ofphotorespiration in the photorespiratory pathway. In this pathway,2-PG is concerned in somephotorespiratory intermediates and is further converted to glycolate, glyoxylate, glycine (Gly), serine (Ser)and resynthesize to glycerate in chloroplast, peroxisome and mitochondrion, respectively.Cotton, Gossypium hirsutm L., is a typical C3plant, and has significantly higher photorespiration rates.In this study, we evaluated the physiological responses of cotton to MeOH foliar application under fieldconditions and report the effects of (i) exogenous MeOH on photorespiratory major metabolitesintermediates levels;(ii) mutation of key enzyme on the activity of photorespiration; and (iii) themechanism of MeOH regulation of photorespiration in cotton.In this study, we investigated the effects of foliar application of MeOH (30%, v/v) on glycolate oxidase(GO) activity and photorespiratory intermediates in cotton leaves in a field experiment. The results showedthat MeOH treatment significantly inhibited GO activity (by29.46%compared with the controls). We alsofound that the levels of endogenous glyoxylate, a photorespiratory intermediate, increased and the levels ofglyine (Gly) decreased significantly in MeOH-treated plants. Interestingly, the levels of serine (Ser)increased significantly in MeOH-treated plants. These results thus demonstrated that the exogenous MeOHcan modulate GO activity and the production of photorespiratory intermediates, and sheds new lights onour current understanding of how exogenous MeOH inhibits photorespiration and enhances C3plants, suchas cotton, growth and yield.