It is well known that high temperature, a typically negative environmental factor, reduces the parasitism of a parasitoid. Generally, high temperature causes the rapid overproduction of reactive oxygen species (ROS) in organisms, and antioxidative enzymes participate in the process of resisting environmental stress by eliminating excess ROS. In the present study, we identify two superoxide dismutase (SOD), one catalase (CAT), six peroxidases (POD), and five glutathione-S-transferase (GST) genes; and the survival rate and antioxidative enzyme patterns under short-term high temperature exposure of the parasitoid wasp, A.asychis, are examined. Survival results of A.asychis reveal that females show higher thermal tolerance than males. Under short-term high-temperature exposure, in females, the expression levels of most antioxidant enzyme genes decreased first and then increased to a peak at 41 °C, while only the expression of AasyGST4 showed a continuous increase. In males, the expression patterns of most antioxidant enzyme genes fluctuated and reached a maximum at 41 °C. Moreover, the expression levels of the majority of antioxidant enzyme genes were higher in females than in males. In addition, at temperatures of and above 35 °C, the activities of these four antioxidant enzymes were induced. The results show that the antioxidant enzymes confer thermo-tolerance to A. asychis against lethal thermal stress. Our observations enrich the understanding of the response mechanism to high-temperature assaults of A. asychis.

Aphelinus asychis is an important aphid endoparasitoid. Under field and greenhouse conditions, high temperature is one of the factors limiting the application of A. asychis for biological pest control. To explore the potential role of transient receptor potential (TRP) channels and heat shock proteins (HSPs) in this process, we identified 11 genes encoding TRP channels and nine genes encoding HSPs. Three proteins (AasyTRPA5, AasyPyrexia, AasyPainless) that belong to transient receptor potential ankyrin (TRPA) subfamily and nine HSPs are involved in the response to high temperature. We also investigated the survival of A. asychis and the response of the identified TRP channels and HSPs to high temperature. The results showed that the maximum temperature that allowed A. asychis survival was approximately 41 degrees C; females had higher survival rates than that of the males at 40 and 41 degrees C. Short-term heat-shock resulted in increased expression of Aasyshsp in males, and Aasyhsp40, Aasyhsp68, Aasyhsp70-4, Aasyhsp70-5 and Aasyhsp90 were upregulated and then downregulated, whereas Aasyhsp70-3 was upregulated at 41 degrees C. Moreover, Aasyhsp40 and Aasyhsp90 showed higher expression levels in females, while Aasyshsp and Aasyhsp70-3 presented opposite expression patterns. At temperature above 35 degrees C, expression of AasyPyrexia in females was significant higher than that in males, whereas AasyPainless and AasyTRPA5 presented higher expression in males at 40 and 41 degrees C, respectively. Altogether, these results indicate that protection against thermal stress in A. asychis is coordinated by TRP channels and HSPs. These findings provide a basis for understanding the potential mechanism of A. asychis in response to high temperatures.