Glutathione: biosynthesis, metabolism and relationship to stress tolerance explored in transformed plants

Crucial roles in sulphur metabolism and plant defence have been described in recent years for the tripeptide thiol glutathione, In spite of this, the metabolism of glutathione and its response to stress conditions remained only partly understood. In many plants, one of the major difficulties in studying the control of glutathione synthesis is the low extractable activities of the enzymes involved. Consequently, several groups have exploited transformation technology using genes for the enzymes of glutathione synthesis or reduction. This approach has allowed the production of plants with systematically enhanced levels of glutathione (up to 4-fold higher than untransformed controls) and has permitted numerous insights into the control of glutathione synthesis or reduction state and its interaction viith other areas of primary or defensive metabolism.