Spiroplasma affects host aphid proteomics feeding on two nutritional resources

Bacterial symbionts are broadly distributed among insects, influencing their bioecology to different degrees. Aphids carry a number of secondary symbionts that can influence aphid physiology and fitness attributes. Spiroplasma is seldom reported as an aphid symbiont, but a high level of infection has been observed in one population of the tropical aphid Aphis citricidus. We used sister isolines of Spiroplasma-infected (Ac-BS) and Spiroplasma-free (Ac-B) aphids reared on sweet orange (optimum host) and orange jasmine (suboptimum host) to demonstrate the effects of Spiroplasma infection in the aphid proteome profile. A higher number of proteins were differently abundant in aphids feeding on orange jasmine, indicating an impact of host plant quality. In both host plants, the majority of proteins affected by Spiroplasma infection were heat shock proteins, proteins linked to cell function and structure, and energy metabolism. Spiroplasma also induced changes in proteins involved in antimicrobial activity, carbohydrate processing and metabolism, amino acid synthesis and metabolism in aphids feeding on orange jasmine. We discuss on how the aphid host proteome is differentially affected by Spiroplasma infection when the host is exploiting host plants with different nutritional values.