Variations in immune responses of the pea aphids Acyrthosiphon pisum feeding on different host plants
Martin John Martin, Li Ma and Zhiqiang Lu
Arthropod-Plant Interactions
https://doi.org/10.1007/s11829-022-09931-y
Abstract
It is well established that host plants influence an insect's immune responses; however, most studies have been conducted on lepidopteran insects; little is known about hemipteran insects, particularly the pea aphid, Acyrthosiphon pisum. Pea aphids feed on host plants by ingesting phloem sap. The chemical composition and concentration of the sap vary depending on the host plant. These differences may impact aphid immune responses to pathogens. In this study, we examined the variations of the immune responses of pea aphids reared on broad beans (Vicia faba) and alfalfa (Medicago sativa). Pea aphids on these two host plants were challenged with bacteria Staphylococcus aureus and Escherichia coli and then the concentration of hydrogen peroxide (H2O2), phenoloxidase (PO) activity, and phagocytosis index were measured. We found that the H2O2 level and PO activity increased in the aphids on these two host plants in response to bacterial infection. In the infected condition, aphids reared on broad beans had higher H2O2 level than those reared on alfalfa, on the contrary, aphids reared on alfalfa had higher PO activity than those reared on broad beans. Furthermore, for both groups of aphids, haemocytes engulfed bacterial cells, and the capacity to phagocytize did not vary significantly between the haemocytes from these two groups of aphids. Our findings suggested that the immune responses of the pea aphid to pathogen are affected by their host plant specifically.