A digestive tract expressing a-amylase influences the adult lifespan of Pteromalus puparum revealed through RNAi and rescue analyses

Authors: WANG, B - Zhejiang University; YANG, Y - Zhejiang University; LIU, M - Zhejiang University; YANG, L - Zhejiang University; Stanley, David; FANG, Q - Zhejiang University; YE, G - Zhejiang University

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/3/2019
Publication Date: 5/3/2019
Citation: Wang, B., Yang, Y., Liu, M., Yang, L., Stanley, D.W., Fang, Q., Ye, G. 2019. A digestive tract expressing a-amylase influences the adult lifespan of Pteromalus puparum revealed through RNAi and rescue analyses. Pest Management Science. https://doi.org/10.1002/ps.5462.
DOI: https://doi.org/10.1002/ps.5462

Interpretive Summary: Classical chemical insecticides are wide used to protect cropping systems from pest insects, although serious issues attend use of chemical insecticides, including pest resistance to the chemicals and large-scale environmental degradation. One alternative to these chemicals is release of large populations of parasitoids into infested fields. Parasitoid insects are generally small wasps that deposit their eggs on or in the bodies or eggs of other insects. The larvae emerge from the eggs and go through their juvenile developmental stages within or on their hosts. The parasitoids consume the hemolymph (blood) and other tissues of their hosts and leave their dead hosts behind when they emerge as adults. Parasitoids provide valuable biocontrol services to agriculture on a global basis and some species are established, commercial agents in pest insect biological control programs. Parasitoids and their hosts live in on-going co-evolutionary relationships. Hosts, of course, respond to parasitoid invasions with very strong immune reactions that encapsulate and kill them and parasitoids evolve countermeasures that down-regulate host immunity. Understanding the detailed mechanisms of these host-parasitoid relationships is necessary to improve parasitoid efficacy as pest management agents. Here, we report on three genes that act in sugar digestion within a parasitoid species. Two of the genes are expressed specifically in the digestive tract, where they digest dietary sugars for uptake into parasitoid bodies. This finding provides necessary new information on the flow and use of biological resources from hosts to parasitoids. It will be used by scientists working to improve the efficacy of parasitoid-mediated biological control of pest insects. This will ultimately benefit consumers at the global level by providing environmentally compatable, safe, effective and reliable management of serious crop pests.

Technical Abstract: Pteromalus puparum (Hymenoptera: Pteromalidae) is an endoparasitic wasp that parasitizes many butterfly species including Brassicaceae pest Pieris rapae. Endoparasitic wasps deposit their eggs and venom in host hemolymph to regulate the immunity and metabolism of the host and promote the development of its offspring. Midgut and salivary gland a-amylases are digestive enzymes required for development and growth of insects and have already been investigated in some insect species, however, a-amylases in the endoparasitic wasps have not been reported. RESULTS: In this study, we cloned three genes encoding a-amylases in Pteromalus puparum, PpAmy1, PpAmy2 and PpAmy3. The full length of the PpAmy1 cDNA is 1,872 bp, encoding 496 amino acids, the PpAmy2 cDNA is 1,863 bp long, encoding 518 amino acids and PpAmy3 cDNA consists of 1,802 bp, encoding 521 amino acids. PpAmys are highly similar in amino acid sequence, but they have separate tissue distributions. PpAmy1 and PpAmy3 are expressed specifically in the digestive tract and the venom apparatus respectively, and PpAmy2 is expressed in all tissues. We report that PpAmy1 acts in the digestive tract, where it influences life span as being demonstrated in our RNAi and a-amylase rescue analyses, PpAmy2 may act in metabolism in muscle-rich tissues, and PpAmy3 may digest host hemolymph carbohydrates for uptake by parasitoid larvae. CONCLUSION: PpAmys have roles in carbohydrate metabolism of parasitoids and host/parasitoid relationships, the characterization and function study of PpAmys lays the foundation for natural enemy resources for agricultural pest control and developing insect-resistant transgenic crop plants.