Chloroplast thiol redox dynamics through the lens of genetically encoded biosensors.

ABSTRACT

Chloroplasts fix carbon by using light energy and have evolved a complex redox network that supports plastid functions by protection against ROS as well as by metabolic regulation according to environmental conditions. In thioredoxin- and glutathione/glutaredoxin-dependent redox cascades, protein cysteinyl redox steady states are set by varying oxidation and reduction rates. The specificity and interplay of these different redox-active proteins are still under investigation, e.g. to understand how plants cope with adverse environmental conditions by acclimating. Genetically encoded biosensors with distinct specificity can be targeted to subcellular compartments such as the chloroplast stroma, enabling in vivo real-time measurements of physiological parameters at different scales. These data have provided unique insights into dynamic behaviours of physiological parameters and redox-responsive proteins at several levels of the known redox cascades. This review summarizes current applications of different biosensor types as well as the revealed dynamics of distinct protein cysteinyl redox steady states with an emphasis on light responses.