Impact of olfactory and visual cues of soybean aphid on the metabolism and stress resistance of Orius sauteri (Poppius)

Abstract

Orius sauteri (Poppius) is the main natural enemy of Aphis glycines (Matsumura) and plays an important role in the biological control of vegetables, forestry, flowers, and farmland ecosystems. In this study, O. sauteri could sense the cues of prey (soybean aphid, Aphis glycines Matsumura) but could not hunt prey. Persistent prey cues could stimulate the olfactory and visual senses and induce the regulation of various metabolic reactions. The activation of food signals increases resistance to starvation stress. To investigate the regulatory methods of prey cues in O. sauteri, we employed an Enzyme-Linked Immunosorbent Assay (ELISA) to detect changes in important enzymes in physiological processes such as energy supply, oxidative stress resistance, and degradation of prey stimulus cues. We found that pyruvate kinase activity was stimulated after O. sauteri smelled the soybean aphid. The peak pyruvate kinase activity in the unfed group was observed after 10 min in the smell treatment group and control group. The first peak value was 28.88 % higher than the other peak values. The peak of enzyme activity in the sight treatment group appeared at 30 min, and it was 29.61 % greater than the peak value of the control group. Furthermore, the expression of HSP70 protein and isocitrate dehydrogenase activity, which are linked to insect stress tolerance, increased to a peak and then quickly declined with olfactory or visual perception time. We also found that carboxylesterase, glutathione S-transferase and acetylcholinesterase activities first increased and then decreased after O. sauteri smelled the soybean aphid. The increased enzyme activity might be linked to resistance to starvation stress and nervous system protection. The olfactory and visual senses of O. sauteri could detect the stimulus cues from soybean aphids which have different regulation effects on key enzymes in physiological processes. The activities of pyruvate kinase, isocitrate dehydrogenase, carboxylesterase, glutathione S-transferase, and acetylcholinesterase were preferentially stimulated by olfactory by visual cues. Visual cues stimulated HSP70 protein expression more than olfactory cues. With the prolongation of food cue sensing time, the intensity of regulation of enzyme activity by the two sensing methods gradually tended to the same level. These results could help us understand the predation and regulation response of O. sauteri to soybean aphids. It provided a reference for the efficient biological control of soybean aphids using O. sauteri.