Reactive oxygen species, antioxidants and the regulation of plant development.

The plasticity of plant growth and development is intricately regulated by endogenous factors, particularly phytohormones such as auxin and cytokinin, and exogenous signals that regulate processes such as axillary bud outgrowth and dormancy. They accumulate in the shoot tip (apical dominance) suppressing the growth of subtending axillary bud. Redox post-translational modifications, triggered by the production of reactive oxygen species (ROS), are important regulators of auxin and cytokinin signalling, and inter-organ communication. ROS act as downstream effectors and, in some cases, inhibitors of cytokinin-mediated pathways, and the redox-dependent multimerisation of the auxin-signalling protein IAA3 influences interactions with other auxin-signalling components to repress downstream gene expression. The antioxidants, ascorbate and glutathione, not only scavenge ROS but also participate in a redox signalling network, through the action of glutaredoxins and other redox mediators. We consider the roles of ROS, ROS-processing proteins, and antioxidants in the regulation of dormancy and axillary bud outgrowth, highlighting novel strategies in managing crop architecture and productivity.