Stress-induced expression of choline oxidase in potato plant chloroplasts confers enhanced tolerance to oxidative, salt, and drought stresses

Transgenic potato plants (Solanum tuberosum L. cv. Superior) with the ability to synthesize glycinebetaine (GB) in chloroplasts (referred to as SC plants) were developed via the introduction of the bacterial choline oxidase (codA) gene under the control of an oxidative stress-inducible SWPA2 promoter. SC1 and SC2 plants were selected via the evaluation of methyl viologen (MV)-mediated oxidative stress tolerance, using leaf discs for further characterization. The GB contents in the leaves of SC1 and SC2 plants following MV treatment were found to be 0.9 and 1.43 μmol/g fresh weight by HPLC analysis, respectively. In addition to reduced membrane damage after oxidative stress, the SC plants evidenced enhanced tolerance to NaCl and drought stress on the whole plant level. When the SC plants were subjected to two weeks of 150 mM NaCl stress, the photosynthetic activity of the SC1 and SC2 plants was attenuated by 38 and 27%, respectively, whereas that of non-transgenic (NT) plants was decreased by 58%. Under drought stress conditions, the SC plants maintained higher water contents and accumulated higher levels of vegetative biomass than was observed in the NT plants. These results indicate that stress-induced GB production in the chloroplasts of GB non-accumulating plants may prove useful in the development of industrial transgenic plants with increased tolerance to a variety of environmental stresses for sustainable agriculture applications.