Climate Change And Redox Signaling

CCARS Team / Graham Noctor

The ongoing increases in greenhouse gases, such as CO₂, will affect plant in two principal ways. First, increased CO₂ will in itself entail adjustments in plant metabolism and physiology. Second, the resulting changes in climate are predicted to lead to increasingly intense periods of stressful conditions. Given their centrality to a myriad of plant functions, alterations in redox status are likely to be key to both these effects.

Through their influence on reversible modifications of protein Cys residues, thiol regulators, such as glutathione and thioredoxins, are key redox players. Both interact closely with reactive oxygen species (ROS) and, in recent years, ROS-triggered redox regulation has received intense interest. As by-products of numerous metabolic pathways, ROS are generated continuously in plant cells but their concentrations are modified by the environment, with accumulation being stimulated by stressful conditions. Further, they can also be pro-actively produced by the plant as a means of signalling the presence of invaders and/or to regulate phytohormone pathways.

Our recent results point to the existence of several novel redox regulatory mechanisms involved in linking stress to SA synthesis and signalling. We use complementary genetic and biochemical approaches to investigate these mechanisms. In particular, we seek to identify the roles of key redox players (glutathione and thioredoxins) in linking environmental changes to activation of SA-dependent adjustments in plant development and stress resistance.

The specific questions we are addressing are:

(1) How do specific redox enzymes link H2O2 to activation of the SA pathway?

(2) What are the relationships between glutathione and SA?

(3) What are the roles of specific thioredoxins in modulating phytohormone biosynthesis and signaling pathways?