Targets of NO in plastids

Nitric oxide (NO) is an important signaling molecule in plants, which regulates many processes in the cell. The various studies have been tried to understand the role of NO in plant cells especially in the chloroplast by exogenous application of gaseous molecule or donor of NO. Here, we review the important target sites of NO in plastids which are directly affected by the exogenous application of NO gas or NO donor, e.g., sodium nitroprusside (SNP). The studies show the positive effect of NO at low concentration (nanomoles) and inhibitory effect of NO at higher concentrations (micro- or millimole) on photosynthetic machinery in chloroplast. NO, thus by interacting with plastids proteins/enzymes, influencing photophosphorylation, electron transport activity, and oxidoreduction state of the Mn clusters of the oxygen-evolving complex, RuBisCo activity, stomatal conductance, and thereby modulating the overall photosynthesis of the plant cells. The detailed modulation of NO-induced changes in the photosynthetic apparatus on its functions and sensitivity are discussed here in this chapter.