Heterologous expression of ApGSMT2 and ApDMT2 genes from Aphanothece halophytica enhanced drought tolerance in transgenic tobacco
The glycine-methylation biosynthetic pathway of glycinebetaine (GB) has been investigated, but only a few studies on GB accumulation in transgenic higher plants have utilized this pathway. In this study, two methyltransferase genes named ApGSMT2 and ApDMT2, encoding proteins catalyzing GB biosynthesis from glycine, were cloned from a relative strain of Aphanothece halophytica. The potential roles of ApGSMT2 and ApDMT2 in GB synthesis were first examined in transgenic Escherichia coli, which had increased levels of GB and improved salt tolerance. Then ApGSMT2 and ApDMT2 were transferred into tobacco. Compared with transgenic tobacco expressing betA, transgenic tobacco co-expressing ApGSMT2 and ApDMT2 accumulated more GB and exhibited enhanced drought resistance with better germination performance, higher relative water content, less cell membrane damage and better photosynthetic capacity under drought stress. We concluded that the ApGSMT2 and ApDMT2 genes cloned in this study will be very useful for engineering GB-accumulating transgenic plants with enhanced drought resistance.
KeywordsCo-expressing ApGSMT2 and ApDMT2 Drought tolerance Glycinebetaine Tobacco
The authors thank Dr. Roberta Greenwood (Shandong University, China) for manuscript writing and helpful advice. This research was supported by Hi-Tech Research and Development (863) Program of China (2007AA10Z175) and National Key Technologies R&D Program (2007BAD31B01).
- 3.Garcia-Perez A, Burg MB (1991) Renal medullary organic osmolytes. Phys Rev 71:1081–1115Google Scholar
- 6.Zhao Y, Aspinall D, Paleg LG (1992) Protection of membrane integrity in Medicago sativa L. by glycinebetaine against the effect of freezing. J Plant Physiol 140:541–543Google Scholar
- 18.Lai MC, Yang DR, Chuang MJ (1999) Regulatory factors associated with synthesis of the osmolyte glycine betaine in the halophilic methanoarchaeon Methanohalophilus portucalensis. Appl Environ Microbiol 2:828–833Google Scholar
- 20.Waditee R, Tanaka Y, Aoki K, Hibino T, Jikuya H, Takano J, Takabe T, Takabe T (2003) Isolation and functional characterization of N-methyltransferases that catalyze betaine synthesis from glycine in a halotolerant photosynthetic organism Aphanothece halophytica. J Biol Chem 7:4932–4942CrossRefGoogle Scholar
- 21.Waditee R, Bhuiyan MN, Rai V, Aoki K, Tanaka Y, Hibino T, Suzuki S, Takano J, Jagendorf AT, Takabe T, Takabe T (2005) Genes for direct methylation of glycine provide high levels of glycinebetaine and abiotic-stress tolerance in Synechococcus and Arabidopsis. Proc Natl Acad Sci USA 102:1318–1323CrossRefPubMedGoogle Scholar
- 27.Rippka R, Deruelles J, Waterbury JB, Herman M, Stanier RY (1979) Genetics assignments, strain histories and properties of pure cultures of cyanobacteria. J Gen Microbiol 111:1–61Google Scholar