LAUSR

Abstract The cellular redox state is vital for the survival of all living systems. The dynamic nature of reactive oxygen species (ROS) are reflected in their functioning both as a damage causal and control agent. They are known primarily for causing oxidative damage and induction of programmed cell death (PCD) in case of pathogen attacks to prevent pathogen proliferation, while at low levels, they act as signal transducer(s) in different signaling pathways. Protein phosphatase(s) and kinase(s) co-ordinate the reversible post-translational modification of proteins, thereby, regulating a number of signaling pathways. In plant systems, protein kinases outnumber the protein phosphatases, which is countered by the diverse functional assemblage of the latter. Protein phosphatases are redox-regulated through reversible oxidation of critical Cysteine (Cys) residues leading to their activation and inactivation. Thus, their diversity and critical involvement in a number of cellular processes, which require redox homeostasis as a crucial element, brings them under the control of redox regulation. The observations made with regard to their involvement in photo-oxidative stress and responses involving ROS as signaling molecules, make a strong case for the potential of protein phosphatases in ROS signaling, with an emphasis on stress biology. In this review, we present the common ground on which ROS and protein phosphatases operate in view of their regulatory functions.