Chapter 2 - Nitric oxide biosynthesis under stressful environments

Abstract

Nitric oxide (NO) is a major signaling biomolecule associated with diverse physiological processes in plants. However, its production in photosynthetic organisms is still ambiguous. The most comprehensive NO production pathway includes the conversion of nitrite (NO3−) to NO via various non-enzymatic or enzymatic mechanisms. Apart from this reductive route, numerous reports indicate the prospect of oxidative NO production in an arginine-dependent pathway by NO synthase (NOS) activity. However, there has been no evidence of the presence of NOS homologs in the genome of embryophytes, and the proteins involved during NOS-like activity in plants are yet to be identified. Current progress searching about the capability of NO in plant stress tolerance has been remarkable. These studies indicate that NO has antioxidant properties and may act as a signal to activate reactive oxygen species scavenging enzyme activities under abiotic stress. NO is essential for resistance to salt, drought, high and low temperatures, UV-B, and heavy metal stress. Promptly increasing evidence recommends that NO is fundamentally required in multiple physiological processes, although, there is extensive discrepancy about the mechanism(s) by which NO relegates abiotic stress.