Current Concepts of the Mechanisms of Nitric Oxide Formation in Plants

Nitric oxide (NO) is a universal signaling molecule that functions in all living organisms. It is involved in the regulation of plant growth and development as well as in the formation of plant resistance to a wide range of stress factors. Along with tremendous progress in understanding the role and mechanisms of NO regulatory action achieved in the past three decades, the pathways of NO biosynthesis in plant organisms are far from being fully understood and remain the subject of heated discussions. Analysis of current literature reveals two principally different mechanisms of NO formation in higher plants: the oxidative or arginine-dependent pathway and the reductive or nitrate/nitrite-dependent pathway. In the first case, nitric oxide is produced during the interaction of arginine with oxygen, which proceeds with the formation of citrulline and the release of an NO molecule. However, the enzymes responsible for oxidative formation of NO in higher plants have not yet been identified. The nitrite-dependent formation of NO is the best studied pathway, in which particular roles belong to molybdenum-containing enzymes, such as nitrate reductase (NR) and the amidoxime reductase mARC (mitochondrial amidoxime reducing component). Xanthine oxidoreductase (XOR), aldehyde oxidase (AO), and sulfite oxidase (SO) may also contribute to NO production. This review presents a detailed analysis of the main mechanisms of NO formation in higher plants.

Automated summary

Nitric oxide (NO) plays a crucial role in plant growth and development as well as in the formation of plant resistance to stress factors. There are two principal mechanisms of NO formation in higher plants: the oxidative or arginine-dependent pathway and the reductive or nitrate/nitrite-dependent pathway.