Nicotinamide mononucleotide confers broad-spectrum disease resistance in plants

Nicotinamide mononucleotide (NMN), a precursor in nicotinamide adenine dinucleotide (NAD) biosynthesis, has long been recognized for its pivotal role in medicine. Recent investigations have suggested its potential as a plant immunity inducer for controlling fungal diseases. However, whether NMN confers plant broad-spectrum resistance against diverse phytopathogens, and its underlying mechanisms remain ambiguous. In this study, we investigate the effect of NMN against multiple phytopathogens in tobacco. Our results demonstrate that tobacco pretreated with NMN exhibits enhanced resistance against Rastonia solanacearum CQPS-1, Pseudomonas syringae DC3000 ∆hopQ1-1, Phytophthora parasitica, and tobacco mosaic virus (TMV). NMN displays effectiveness within the concentration range of 50-600 μM, with 75 μM NMN exhibiting the most pronounced effect. The impact of NMN pretreatment could persist for up to 10 days. Beyond tobacco, NMN pretreatment enhances disease resistance in tomato and pepper plants against diverse pathogens, underscoring NMN's capacity to confer broad-spectrum disease resistance in crops. Moreover, RT-qPCR analysis reveals that NMN significantly upregulates the expression of the pattern-triggered immunity (PTI) marker gene NbCYP71D20 and salicylic acid (SA) marker gene NbPR1a. This suggests that NMN enhances plant resistance by inducing both PTI and SA-mediated immunity. Interestingly, the positive impact of NMN on plant disease resistance is not significantly compromised in both NMN adenylyltransferase (NMNAT)-silenced plants and NAD receptor mutant lecrk-I.8, suggesting the existence of NAD-independent signaling pathways for NMN-induced plant immunity. In conclusion, our study establishes that the bioactive molecule NMN imparts broad-spectrum disease resistance in plants, offering a simple, environmental-friendly, and promising strategy for safeguarding crops against diverse phytopathogens. These findings also provide valuable insights for future in-depth studies into the functional mechanisms of NMN.