Does Transformation with the codA Gene Have Harmful Effects?
Metabolic engineering of the synthesis of certain compatible solutes, such as sorbitol, has pleiotropic effects, for example necrosis and the development of growth defects, which are mostly due to disturbances in endogenous pathways of primary metabolism (Sheveleva et al., 1998). We were concerned that the overexpressed COD might compete for choline with the enzymes involved in the biosynthesis of phosphatidylcholine, a major component of membrane lipids. In fact, we found no significant differences in the respective levels of choline and phosphatidylcholine between transgenic and wild-type plants (Hayashi et al., 1997; Alia et al., 1999). Another concern was that COD might generate high levels of H2O2 as a by-product of the synthesis of GB. The level of H2O2 increased only modestly (1.5- to 2.0-fold) in transgenic plants under both stress and non-stress conditions, as compared with levels in non-transgenic plants (Alia et al., 1999). Simultaneously with the slight increase in the leve
