Effect of Drought Stress on Proline and Betaine Metabolic Pathway in Cynodon dactylon
To investigate the mechanisms of drought resistance of proline and betaine in bermudagrass.The drought-sensitive Cd32 and drought-resistant Cd138 bermudagrass genotypes were used to investigate the differences in substrate content and enzyme activities related to proline and betaine metabolism in the two types of bermudagrass in response to the three drought treatments.The results showed that compared with normal irrigation,the contents of proline and betaine in roots and leaves were significantly increased after moderate and severe drought stress,and reached the peak value under severe stress,and the contents in leaves was higher than those in roots.The proline contents of Cd138 Cd32 were significantly different under drought stress.The content of ornithine,the metabolic substrate of proline in the leaves and roots of two bermudagrass,reached its peak in moderate drought,while the content of glutamate increased in the roots and Cd32 leaves,and decreased in Cd138 leaves with the intensities of drought.The activities of P5CR and P5CS increased first and then decreased with drought,significantly increased compared with the control,while the activities of P5CDH and ProDH decreased significantly,resulting in enhanced synthesis and inhibited of proline decomposition,especially in Cd138 leaves.The activities of BADH and CMO,two key enzymes in the betaine synthesis pathway of Cd138,increased with drought,and the CMO activity of Cd32 reached a peak value(8.54 U/g)during moderate drought,but was still lower than that of Cd138(8.99 U/g).In conclusion,bermudagrass can alleviate the damage caused by drought stress by promoting the metabolism of proline and betaine,which is mainly through Glu pathway.In the metabolism of betaine,CMO decreases in Cd32 under moderate and severe drought,but still maintains a higher activity in Cd138,which may be one of the reasons why Cd138 is more drought-resistant than Cd32.
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