| Budget Amount *help |
¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 1998: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1997: ¥2,000,000 (Direct Cost: ¥2,000,000)
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| Research Abstract |
Glycinebetaine (GB), a quaternary ammonium compound, is regarded as one of the most effective osmoprotective compounds. Rice can not synthesize GB due to absence of the activities of the two enzymes required for its biosynthesis. In plants GB is synthesized by the two-step oxidation of choline via the intermediate betaine aldehyde which catalyzed by choline monooxygenase and betaine aldehyde dehydrogenase.
This project was aimed to engineer new rice with tolerance against environmental stresses such as barley, and was evaluated the effect of GB on tolerance against cold and heat or on growth in rice, transgenic rice plants overexpressing the enzyme were produced by the introduction of a cDNA clone for betaine aldehyde dehydrogenase of barley. The results were first, that GB supplied and accumulated exogenously in rice plants inhibited clearly the length of shoot and root but enhanced the dry weight of shoot and root. However, a significant tolerance against cold and heat stresses were conferred. Second, the transgenic rice plants converted high levels of exogenously applied betaine aldehyde (up to 10 mol m^<-3>)to GB more efficiently than wild type plants did. A higher level of GB accumulated in the transgenic rice plants conferred significant tolerance against cold and heat stresses. However, the higher levels of glycinebetaine accumulated endogenously in the transgenic rice plants inhibited the growth of the rice plants based on the length (elongation), but not based on the dry weight.
The engineering of new rice is completed if a gene encoding choline monooxygenase will be introduced to the transgenic plants overexpressing a gene encoding betaine aldehy dedehydrogenase of barley.
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