Regulation and Function of Protein S-Nitrosylation in Plant Stress

Post-translational modification (PTM) of proteins serves as a major regulatory check-point for cellular signaling processes during stress-related responses. S-Nitrosylation is a nitric oxide (NO) dependent PTM wherein NO reacts with the thiol group of redox-sensitive cysteine residue of the proteins. Accumulation of NO is often associated with stress in plants and many regulatory proteins involved in stress-induced signaling carries redox-sensitive cysteine residue, which makes S-nitrosylation a potentially important PTM. However, like any other signaling event, S-nitrosylation is also highly regulated. The unique chemistry of NO to exist in different reactive forms and the spatio-temporal regulation on their reactivity towards the target thiols is the driving force of S-nitrosylation signaling mechanism. Attempts to study the precise mechanism responsible for S-nitrosothiol formation have been hampered due to the technical limitations caused by extremely dynamic nature of this signaling event and the variety of reactions that NO undergo. However, the role of S-nitrosylation in regulating various biological processes in plants is now evident. This chapter will focus on the mechanism of S-nitrosylation and its regulation and function in plant stress.