The glutaredoxin gene family in wheat functions beyond redox homeostasis regulation

The main function of glutathione (GSH) in the cell is to act as a redox buffer against irreversible damage to cell machinery caused by a build up of reactive oxygen species (ROS). Other functions of glutathione in the cell include xenobiotic and heavy metal detoxification, signalling in plant-pathogen interactions as well as plant developmental processes and cell cycle control1. Because glutathione can form bonds to thiols of proteins, and can be enzymatically transferred and removed, it provides an interesting way by which protein activity can be modulated as has been shown for NF-κB in humans2 and NPR1 in Arabidopsis3. Glutaredoxins (GRXs) are glutathione dependant oxidoreductase enzymes which mediate the reversible reduction of disulphide bonds of proteins and proteinglutathione mixed disulphides and are found in all freeliving organisms4,2. Apart from their obvious role in the regulation of redox balance, plant glutaredoxins have been shown to bind iron sulphur centres5, regulate defensin expression6 and be crucial for flower development7,8. Glutathionylation is now being seen as a reversible post translational modification analogous to phosphorylation and inherently linked to cellular redox potential. In order to obtain a greater understanding of the role of glutathionylation, it is necessary to study redox active protein families such as glutathione S-transferases (GSTs) and GRXs. This paper describes aspects of GRX gene expression in wheat and the potential role of three GRX genes in inflorescence development.