Genetic Engineering of Biosynthesis of Glycinebetaine Enhances Tolerance to Various Stress

摘要

Many halotolerant plants, bacteria and algae accumulate glycinebetaine (betaine) in response to environmental stress such as high concentrations of salt, low temperature and drought. In stressed cells, betaine acts to stabilize the structures and maintain the functions of proteins and membranes. In an effort to generate plants capable of the biosynthesis of betaine, the codA gene for choline oxidase, the enzyme that synthesizes betaine, was isolated from the soil bacterium Arthrobacter globiformis. Then Arabidopsis thaliana was transformed with a modified codA gene that encoded choline oxidase with a sequence for transport into chloroplasts. The resultant transgenic plants were more tolerant to cold, heat and salt stress than the wild-type plants during both the germination of seeds and the growth of young plants. Seeds from the transgenic plants also tolerated cold and heat stress during imbibition. Moreover, fluorescence studies revealed that transformation with the codA gene allowed the photosynthetic machinery of the transgenic plants to tolerate cold, salt and high-light stress. Thus, betaine that accumulated in the choloroplasts of the transgenic plants allowed the plants to tolerate a variety of stress at various stages of development. Similar transgenic rice plants also tolerated cold and salt stress.