Salinity affects metabolomic profiles of different trophic levels in a food chain

Salinization is one of the most important abiotic stressors in an ecosystem. To examine how exposing a host plant to excess salt affects the consequent performance and metabolism of insects in a food chain, we determined the life history traits and the metabolite profiles in rice (Oryza sativa), the herbivore Sitobion avenae, and its predator Harmonia axyridis. When compared with performance under normal (non-stressed) conditions, exposing plants to 50mM NaCl significantly delayed the timing of development for S. avenae fed on rice and H. axyridis and also reduced the body mass of the latter. Our GC–MS-based analysis revealed clear differences in metabolite profiles between trophic levels or treatment conditions. Salinity apparently increased the levels of main components in rice, but decreased levels of major components in S. avenae and H. axyridis. In addition, 16 metabolites showed salinity-related contrasts in this trophic interaction for our rice–S. avenae–H. axyridis system. Salinity impeded the accumulation of metabolites, especially several sugars, amino acids, organic acids, and fatty acids in both insects, a response that was possibly associated with the negative impacts on their growth and reproduction under stress conditions. Changes in plant metabolites due to salinity strongly influenced the concentrations of metabolites in herbivorous and predatory insects in a food chain. [Display omitted] •We tested the effect of salt on metabolites in a plant–herbivore–predator system.•Differences in metabolites between trophic levels or salt conditions were found.•Salinity significantly increased the levels of main components in rice plant.•In contrast, levels of major components in herbivores and predators were reduced.•These might be correlated with inhibitive effects on insect growth under salinity.