Fatty Alcohols, a Minor Component of the Tree Tobacco Surface Wax, Reduce Insect Herbivory

Abstract

Despite decades of research resulting in a comprehensive understanding of epicuticular wax biosynthesis and metabolism, the function of these almost ubiquitous metabolites in plant-herbivore interactions remains unresolved. To develop a better understanding of this role, we investigated plant-herbivore interactions in four Nicotiana glauca (tree tobacco) genome edited mutants. This included [eceriferum1 (cer1), eceriferum3 (cer3), beta-ketoacyl-coA synthase6 (kcs6), and fatty acyl-coA reductase (far)] displaying a wide range of alkane and fatty alcohol abundances. Three interaction classes were examined: chewing herbivory with seven caterpillar and one snail species, phloem feeding with Myzus persicae (green peach aphid), and egg laying with Bemisia tabaci (sweet potato whitefly). We found that high wax load and alkane abundance did not reduce caterpillar or snail herbivory. However, fatty alcohol content was negatively correlated with caterpillar growth, suggesting a role in reducing insect herbivory despite its lower levels. Aphid reproduction and feeding activity were not correlated with wax load and composition but are potentially affected by altered cutin composition of cer1 mutants. When examining non-feeding activities, wax crystal morphology could explain the preference of B. tabaci to lay eggs on wildtype plants relative to cer1 and far mutants. Accordingly, the fatty alcohol wax component reduces caterpillar herbivory on the chemical level, but oviposition is increased when wax crystals are dense. The results suggest that this varied response between herbivore classes and species, at times displaying increased and at times reduced fitness in response to altered wax composition is in part a consequence of co-evolution that shaped the specific effects of different N. glauca metabolites such as anabasine and fatty alcohols in plant-herbivore interactions.

Trade‐offs between the accumulation of cuticular wax and jasmonic acid‐mediated herbivory resistance in maize

“…Although enhanced herbivore resistance has been reported in other plant species (Way and Murdie, 1965; Mori, 1982; Negin et al, 2021, 2023), our study is the first to show a consistent trade‐off between wax production and herbivore‐induced JA biosynthesis in maize (Figures 4, 5). Connections between lipid fluxes for wax and JA biosynthesis were previously suggested in cotton ( Gossypium hirsutum ) and orange ( Citrus × sinensis ) plants.…”

Are epicuticular waxes a surface defense comparable to trichomes? A test using two Solanum species and a specialist herbivore

“…Toxins in the leaf wax may contribute to this inhibitory effect (Belete, 2018). For instance, Negin et al (2021) found that fatty alcohols in the epicuticular waxes of Nicotiana glauca (Solanaceae) tend to reduce caterpillar growth. In our experiment, mass gain was lower in caterpillars placed on S.…”

Knockout mutations ofNicotiana benthamianadefenses reveal the relative importance of acylsugars, nicotine, and a serine protease inhibitor in a natural setting

“…After 11 days, survival was scored, and live caterpillars were weighed. This timeframe was chosen following a previous trial with Nicotiana glauca in which S. exigua larvae were confined on leaves for a similar duration (Negin et al ., 2024). Four-day-old C. virescens larvae hatched on beet armyworm diet were weighed, and those weighing 5-12 mg were placed in organza mesh bags on individual N. benthamiana leaves, with a single caterpillar in each bag.…”