Abstract
Nicotinamide (NAM) alters behavior in C. elegans and Drosophila, serving as an agonist of TRPV channels affecting sensory neurons and mimicking the mode of action of insecticides used to control phloem-feeding insects. The impact of NAM on green peach aphid (Myzus persicae) behaviors was assessed in artificial diet assays and foliar applications to Arabidopsis plants. Aphids feeding on artificial diets supplemented with NAM impaired stylet movement causing feeding interruptions and ultimately starvation and death. Aphid feeding behaviors were negatively impacted on NAM sprayed plants at concentrations as low as 2.5 mM leading to increased mortality. In choice assays with NAM sprayed leaves aphids showed clear preference for untreated control leaves. NAM is an intermediate in the NAD salvage pathway that should accumulate in nicotinamidase (nic) mutants. LC-MS analysis showed NAM accumulates 60-fold in nic-1-1 Arabidopsis mutants as compared with Col-0. Aphid reproductive potential was significantly decreased on nic-1-1 mutant plants, resulting in a smaller colony size and arrested population development. The results support the hypothesis that dietary NAM causes behavioral changes in aphids, including altered feeding, reduced reproduction, and increased mortality. NAM is thought to bind to TRPV channels causing overstimulation of sensory neurons in the aphid feeding apparatus.
Highlights
Nicotinamide (NAM) is ubiquitous metabolite found in all living organisms as an intermediary compound in the synthesis of the coenzyme nicotinamide adenine dinucleotide (NAD)
NAM was investigated for its effects on phloem-feeding aphids and its ability to induce behavioral changes that are often regulated by TRPV channels
Nymphs continued to accumulate in the control and 0.001 M NAM diets throughout the 48-hour observation period
Summary
Nicotinamide (NAM) is ubiquitous metabolite found in all living organisms as an intermediary compound in the synthesis of the coenzyme nicotinamide adenine dinucleotide (NAD). Pymetrozine, pyrifluquinazon, and afidopyropen are small synthetic molecules commonly used as insecticides These compounds bind TRPV receptors, impacting sensory functions in sap-sucking insects such as aphids, whiteflies, sharpshooters, psyllids and plant hoppers[13,14]. Drosophila Nan is more broadly expressed in chordotonal and multidendritic neurons, whereas, Iav is restricted to the chordotonal neurons only Both proteins bind pymetrozine and afidopyropen in a competitive manner, with the latter showing higher affinity for Drosophila TRPV channels[17]. Since NAM and pymetrozine bind to the same receptor, it was hypothesized that they would have similar behavioral responses in aphids, leading to feeding cessation and resulting in starvation and death
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