Nitric oxide (NO) and salicylic acid (SA): A framework for their relationship in plant development under abiotic stress

Abstract

The free radical nitric oxide (NO) and the phenolic phytohormone salicylic acid (SA) are signal molecules which exert key functions at biochemical and physiological levels. Abiotic stresses, especially in early plant development, impose the biggest threats to agricultural systems and crop yield. These stresses impair plant growth and subsequently cause a reduction in root development, affecting nutrient uptake and crop productivity. The molecules NO and SA have been identified as robust tools for efficiently mitigating the negative effects of abiotic stress in plants. SA is engaged in an array of tasks under adverse environmental situations. The function of NO depends on its cellular concentration; at a low level, it acts as a signal molecule, while at a high level, it triggers nitro-oxidative stress. The crosstalk between NO and SA involving different signalling molecules and regulatory factors modulate plant function during stressful situations. Crosstalk between these two signalling molecules induces plant tolerance to abiotic stress and needs further investigation. This review aims to highlight signalling aspects of NO and SA in higher plants and critically discusses the roles of these two molecules in alleviating abiotic stress.

Salicylic Acid and Nitric Oxide: Insight Into the Transcriptional Regulation of Their Metabolism and Regulatory Functions in Plants

“…Drought-affected plants exhibit prolonged stomatal closure, decreased relative water content, and increased membrane damage that adversely limits their cellular and metabolic activities (Prakash et al, 2021) (Chavoushi et al, 2019). In addition, foliar application of SA at varying concentrations (0.5-2.0 mM) induced transcriptional reprogramming of several TFs such as Dehydration responsive element binding protein (DREB), AP2/ERF, WRKY, and HSPs that significantly contributed toward enhanced immunity of crop plants against drought stress (Lee et al, 2019).…”

“…Perception of an invader leads to transcriptional regulation of signaling molecules such as SA, NO, JA, ABA, polyamines, etc., that play a vital role in regulating downstream genes involved in strengthening defense response (Prakash et al, 2021). Commonly, SA is believed to be most effective against biotrophic pathogens by modulating SAR.…”

“…In contrast, ABA has been well-documented to stimulate NO generation in guard cells which is vital for activating ABAinduced stomatal closure (Prakash et al, 2021). Furthermore, polyamines, methylglyoxal, and spermidine can differentially regulate defense-related responses to improve plant growth; however, their actions can be reversed by SA-NO mediated signaling (Prakash et al, 2021).…”

Regulatory hubs in plant stress adaptation

“…In terms of phytohormone metabolism, COR induces the synthesis of JA and ET, but suppresses CKand SA-related pathways. Prakash et al (2021) reviewed the roles of SA and nitric oxide (NO) in plant stress responses, focusing on the crosstalk between SA and NO, and SA-and NO-mediated regulation of stress-responsive genes. Khan et al (2021) emphasized the significance of phosphorus (P) balance in regulating plant defence systems.…”

“…Prakash et al . (2021) reviewed the roles of SA and nitric oxide (NO) in plant stress responses, focusing on the crosstalk between SA and NO, and SA‐ and NO‐mediated regulation of stress‐responsive genes. Khan et al .…”