Nitric Oxide as a Signal in Inducing Secondary Metabolites During Plant Stress

Abstract

Secondary metabolites are the major defense elements of plants against biotic and abiotic stress conditions. They are diverse and valuable natural products induced by a variety of environmental and developmental cues. In recent years, NO has been successfully used as elicitor to stimulate secondary metabolite accumulation in plants. Emerging evidence has established the significant role of NO in plant growth and defense responses in plants. Several abiotic and biotic stress factors can induce NO-mediated regulation of the biosynthetic pathways of metabolites that can consequently alter their biological reaction toward the given stress. Moreover, exogenous treatments with NO donors also enhanced the accumulation of secondary metabolites including phenolics, flavonoids, and caffeic acid derivatives in several species suggesting the importance of NO accumulation for the secondary metabolic production. Complete elucidation of its role in the production of such secondary metabolites which are pharmaceutically significant is very essential for improving the large-scale commercial production and enhancing stress resilience in plants. Although several reports suggested the induction of secondary metabolites and NO against a range of stress factors, to establish link between NO and secondary metabolites under stress needs a deeper investigation. This compilation chiefly summarize NO biosynthesis, signaling, and functions under abiotic stress in plants highlighting what is currently known about secondary metabolite induction by NO in plants.