Abstract
Nicotinamide mononucleotide (NMN), a precursor of nicotinamide adenine dinucleotide (NAD), is known to act as a functional molecule in animals, whereas its function in plants is largely unknown. In this study, we found that NMN accumulated in barley cultivars resistant to phytopathogenic fungal Fusarium species. Although NMN does not possess antifungal activity, pretreatment with NMN and related metabolites enhanced disease resistance to Fusarium graminearum in Arabidopsis leaves and flowers and in barley spikes. The NMN-induced Fusarium resistance was accompanied by activation of the salicylic acid-mediated signalling pathway and repression of the jasmonic acid/ethylene-dependent signalling pathways in Arabidopsis. Since NMN-induced disease resistance was also observed in the SA-deficient sid2 mutant, an SA-independent signalling pathway also regulated the enhanced resistance induced by NMN. Compared with NMN, NAD and NADP, nicotinamide pretreatment had minor effects on resistance to F. graminearum. Constitutive expression of the NMNAT gene, which encodes a rate-limiting enzyme for NAD biosynthesis, resulted in enhanced disease resistance in Arabidopsis. Thus, modifying the content of NAD-related metabolites can be used to optimize the defence signalling pathways activated in response to F. graminearum and facilitates the control of disease injury and mycotoxin accumulation in plants.
Highlights
Plants protect themselves from pathogen attack by activating a variety of defence responses, including the production of antimicrobial compounds and proteins[1]
NMN is a precursor of nicotinamide adenine dinucleotide (NAD), which functions as a cofactor for many enzymes involved in the catalysis of various metabolic reactions[21]
Zhang & Mou[9] reported that extracellular NAD induced PR gene expression and resistance against the bacterial pathogen P. syringae in Arabidopsis thaliana. These results suggest that NMN is involved in plant disease resistance against Fusarium species
Summary
Plants protect themselves from pathogen attack by activating a variety of defence responses, including the production of antimicrobial compounds and proteins[1]. NMN activates disease resistance against F. graminearum in Arabidopsis leaves and flowers. We examined the effect of NMN pretreatment on disease resistance against F. graminearum in Arabidopsis plants.
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