Nitric oxide responsive NAD(P)-binding Rossman-fold superfamily protein NONBR negatively regulates the growth and immunity of Arabidopsis thaliana

Background Nitric oxide plays a pivotal role in governing various biological and physiological processes in plants, including growth, development, hormone signaling, and defense responses against both biotic and abiotic stresses. Here we investigate the role of the NO-responsive ATNONBR gene in influencing the growth and immunity of Arabidopsis thaliana atnonbr mutant plants in comparison to WT and other relevant control lines under oxidative (induced by H ₂ O ₂ and methyl viologen), and nitro-oxidative (induced by the NO donors CySNO and GNSO) stress conditions. Results Our findings revealed that, under these conditions, the atnonbr plants exhibited longer roots and shoot lengths compared to WT plants. In addition, to elucidate the role of ATNONBR in basal defense, R-gene mediated resistance and SAR, plants were inoculated with the virulent strain of hemi-biotrophic bacterial pathogen Pseudomonas syringae pv. tomato Pst DC3000 as well as virulent strain ( Pst DC3000 avr B). The atnonbr knockout mutant line exhibited a significantly resistant phenotype, elevated expression of AtPR1 , AtPR2 , AtG3dph , and AtAZI along with enhanced SA accumulation and reduced electrolyte leakage indicating that At1G07450 negatively regulates the basal defense, R -gene-mediated resistance, and SAR in A. thaliana . Further data mining was employed to determine the basal expression of ATNONBR in various plant parts which also indicated significant reduction in its expression in response to multiple biotic and abiotic factors. Furthermore, computational analysis predicted physical interaction of ATNONBR with two other proteins of the same family and several other proteins with high confidence. Besides, two cysteine molecules were detected with high confidence scores as potential targets of S-Nitrosylation by NO, closer to the NADP binding site as well as the substrate and active sites. Conclusion Our study indicates that ATNONBR negatively regulates root and shoot lengths in Arabidopsis thaliana under redox stress conditions, while also exerting a negative influence on its immunity. Additionally, computational analysis predicted its interaction with other proteins and has two cysteine residues as potential targets for S-Nitrosylation.