Nitric Oxide

Abstract

In plants, the gas nitrogen monoxide, commonly called nitric oxide (NO), has recently emerged as a key signaling molecule. In this chapter, we will look at the probable sources of endogenous NO, identify the biological processes that NO can mediate, and explain the downstream signaling systems that NO uses to exert its cellular effects. It is becoming increasingly important to devise methods for quantifying and releasing intracellular NO production. It is also necessary to classify the origins of NO synthesis. NO is often produced from radicals by nitrate enzyme (NR), and, though organic chemistry and medical specialty information indicate the presence of enzyme(s) similar to class NO synthase (NOS), the NOS genes are still unknown. NO exerts effects on a variety of functions in plants, including the production of defense-related genes and programmed necrobiosis, stomatal closure, seed germination, and root formation. Intracellular signaling responses to NO include the production of cyclic guanosine monophosphate, cyclic adenosine 5′-diphosphate ribose, and the increase of cytosolic metals. However, the specific organic chemistry and cellular nature of those reactions have not been determined in numerous situations. Priorities for analysis should include reliable quantification of downstream signaling molecules in NO-responsive cells, as well as biological study and modification of the enzymes involved in the production and degradation of those molecules.