Abstract
Glycinebetaine (betaine) is one of the compatible solutes and is accumulated in a large number of organisms in response to stress conditions. It has been demonstrated in transgene systems that betaine enhances tolerance against various kinds of stress. Synechococcus sp. PCC7942 which has been transformed with the codA gene retains the ability to accumulate betaine when choline is exogenously supplied as the substrate. We found that the transformation enhanced the tolerance of cell against cold stress via the increased ability to repair the photodamaged photosystem II. However, at normal growth temperature, the betaine synthesized in vivo only slightly enhanced the tolerance to photoinhibition. This observation may suggest that the repair of photodamaged photosystem II is sufficiently fast under normal growth conditions and is not enhanced further by betaine. We are now characterizing the effect of betaine on photoinhibition under salt stress.
