Mechanisms of Nitric Oxide Involvement in Plant-Microbe Interaction and Its Enhancement of Stress Resistance

As a highly active signaling molecule, nitric oxide (NO) is a key factor in regulating plant growth and development. Nitric oxide can promote the formation of symbionts between plant roots, rhizobia and AMF, which improves plant access to nitrogen and phosphorus nutrients in the soil. As a signaling molecule, NO regulates plant resistance to biological and abiotic stresses through the following mechanisms: 1) NO interacts with ROS to regulate reactive oxygen levels and mitigate the damage of oxidative stress response on plants; 2) NO regulates plant immunity and stress resistance through post-translational modification of proteins; 3) NO interacts with various plant hormones and is involved in the regulation process of plant growth and development by hormones. In addition, NO can promote the expression of genes related to the formation and development of the symbionts, inhibit the expression of immune genes, and maintain the REDOX level and energy state of the symbionts through the cycle of NO and phytoglobin, thereby enhancing the plant microbial symbiosis. Previous studies on NO have mainly focused on the first three aspects, and there have been few studies on the mechanism of NO in plant-microbe interaction, therefore the involvement of NO in the mechanism of plant-microbe interaction should be strengthened. It is of great theoretical and practical importance to uncover the mechanism of NO enhancement of plant stress resistance and regulation of root development and to study the mechanism of NO regulation of plant-microbe interactions, responses to abiotic stresses, stomatal regulation, and a range of developmental processes. Combined with recent advances in plant NO biology, this review will highlight some key aspects that need further attention.