Published by Oxford University Press [2005] on behalf of the Society for Experimental Biology.
Preface to Redox Regulation of Leaf Metabolism
In the last few years a number of new and exciting aspects of redox regulation of leaf metabolism have been revealed and the focus papers here aim to summarize some of this work.Redox signals are important regulators of chloroplast metabolism. The chloroplast ferredoxin/thioredoxin system elucidated in the 1970s is known to link the activities of stromal enzymes to light. Recently, a novel mechanism has been discovered suggesting that chloroplast lumenal proteins can be oxidatively activated in the light via thioredoxin. The application of proteomic technology has also revealed further roles for thioredoxins in the chloroplast, mitochondria, and cytosol. Furthermore, a role for redox regulation of enzymes in the starch, lipid, and amino acid biosynthetic pathways has also been demonstrated recently. Taken together these papers provide evidence showing that thioredoxin plays a widespread role in the co-ordination of leaf metabolism.
Redox sensing systems also initiate mechanisms that allow the dissipation or avoidance of excess excitation energy. The study of mechanisms involved in the sensing and maintenance of redox poise in the chloroplast has been a major focus of the work in this area. Short-term responses to changes in the redox state that result in the formation of reactive oxygen species have been shown to involve peroxiredoxins and glutathione peroxidase. Additionally, it has been demonstrated that the malate valve helps to maintain the NADPH/ATP ratio in the chloroplast stroma. Longer term changes involve changes in gene expression mediated either by signals transmitted by redox shifts in cellular redox components or by signals transmitted by secondary messengers synthesized inside chloroplasts. These recent discoveries have begun to shed light on the complex nature of redox sensing and signalling in plants.
I would like to thank both the authors and the Journal of Experimental Botany editorial staff for producing these focus articles in a very short space of time, allowing them to be available in print at the International Botanical Congress, Vienna 2005, where the papers will be presented as talks in the session Redox Regulation of Leaf Metabolism.
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