Advances in studies on the role of nitric oxide in plant development and plant-microbial interactions

Nitric oxide (NO), as a highly active signaling molecule, is a key factor to regulate plant growth and development. NO can improve the resistance of plants to biotic and abiotic stresses in order to enhance the immunity of plants. Recent studies have shown that NO also plays an important role in the interaction between plant roots and microbes, for example, NO can promote the symbiosis of plant roots with rhizobia or arbuscular mycorrhizal fungi, thus improving plant’s access to soil nitrogen and phosphorus. As a signal substance, NO regulates plant resistance to biotic and abiotic stresses through the following mechanisms: (1) NO interacts with the reactive oxygen species (ROS) system to regulate ROS level and alleviate oxidative stress; (2) NO regulates plant immunity and stress resistance processes through post-translational modification of proteins; (3) NO interacts with a variety of plant hormones to participate in the regulation of plant hormones on plant growth and development. Moreover, NO can promote the expression level of genes related to the formation and development of symbiosis, inhibit the expression of immune genes; and maintain the redox level and energy status of symbiosis by NO-phytoglobin cycle, thus promoting the symbiotic relationship. There is a need to deeply explore to uncover the mechanisms of NO’s involvement in plant-microbial interaction as well as its enhancement of plant stress resistance, and regulation of root development for improved nutrient utilization efficiency and crop productivity in intensive crop production systems.