Response Of Transformed Tobacco With Betaine Aldehyde Dehydrogenase Gene To Low Temperature Stress

Glycinebetaine(GB) is a compatible so lute that accumulates in certain plants and microorganisms in response to various types of stress. In this study, we elucidate the responses of transformed tobacco plants with betaine aldehydrogenase gene to low temperature stress. The main results are as follows:(1) Low temperature stress resulted in a decrease in CO2 assimilation and such a decrease was much greater in wild type plants than in transgenic plants. During low temperature stress, transgenic tobacco plants maintained higher photosynthetic rate and enhanced the tolerance to low temperature stress.(2) The analyses of chlorophyll fluorescence demonstrated that photosystem II(PSII)in transgenic plants showed higher chilling tolerance than in wild type plants, suggesting that the accumulation of GB leads to increased tolerance to low temperature-enhanced photoinhibition. This increased tolerance was associated with an improvement of oxygen-evolving complex and the reaction center of PSII to low temperature stress.(3) Low temperature stress increased the SOD activity and decreased the CAT activity, the transgenic tobacco plants maitained higher activities of SOD and CAT. Meanwhile the AsA and GSH content in transgenic plants were higher than wild-type plants.The higher antioxidant enzyme activities and antioxidants content in transgenic plants reduced the oxidative stress and enhanced the tolerance to low temperature stress of photosynthesis.(4) Transgenic tobacco plants enhance the accumulation of sucrose and proline, which were as osmoregulation substances to play an important role in low temperature stress.(5) The transgenic tobacco with BADH gene maintains the integrity of the thylakoid membrane, increased the stability of thylakoid membrane under low temperature stress.In conclusion, the mechanisms of the enhanced tolerance to low temperature stress in transgenic tobacco plants with BADH gene maybe associated with the followings: Transgenic tobacco plants decreased the damage induced by ROS to photosynthetic apparatus through maintaining relatively higher antioxidant enzyme activities and antioxidants content. GB in vivo enhanced the tolerance of photosynthesis to low temperature stress.