Genetic and biochemical approaches used for identification and mechanistic characterization of nitric oxide-responsive plant genes.

Nitric oxide (NO) is a multiregulatory signal molecule that integrates development and stress responses. To elucidate the molecular mechanisms of NO phytoeffects and to identify NO-associated genes, both genetic screens and genome-wide transcriptome analysis have been employed in numerous studies. Forward genetic screens have linked NO signalling to key biological processes, such as photosynthesis, cytokinin metabolism, stress adaptation, and cell cycle regulation. Reverse genetics has further characterized the role of NO-related genes involved in NO biosynthesis (e.g., NIA1/NIA2, NOA1), signalling (e.g., GSNOR, NPR1), stress responses (e.g., ABI4, RBOHD), and development (e.g., HO1, NOX1). Across multiple plant species, high-throughput transcriptomic techniques have identified thousands of NO-responsive genes involved mainly in hormonal signalling, carbohydrate metabolism, cell wall formation and stress responses. Beyond transcriptional control, NO has been found to influence gene expression through epigenetic mechanisms, such as histone acetylation and methylation, as well as DNA methylation. Nitric oxide also modifies key transcription factor families, altering their stabilities, DNA-binding capacity, and protein-protein interactions. Overall, this review underscores the central role of NO in modulating gene expression through multiple regulatory layers in plants.