Location: Biological Control of Insects ResearchTitle: Parasitization by Macrocentrus cingulum (Hymenoptera: Braconidae) influences expression of prophenoloxidase in Asian Corn Borer Ostrinia furnacalis Author
Submitted to: Archives of Insect Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/9/2011
Publication Date: 4/1/2011
Citation: Feng, C., Huang, J., Song, Q., Stanley, D.W., Lu, W., Zhang, Y., Huang, Y. 2011. Parasitization by Macrocentrus cingulum (Hymenoptera: Braconidae) influences expression of prophenoloxidase in Asian Corn Borer Ostrinia furnacalis. Archives of Insect Biochemistry and Physiology. 77:99-117. Interpretive Summary: Long term agricultural sustainability is severely threatened by widespread use of classical insecticides. Threats include increasing resistance to insecticides and decreasing environmental quality. The concept of biological control of insect pests is a potentially powerful alternative to classical insecticides. Biological control is based on deploying insect-specific predators and parasites to reduce pest insect populations to a point of negligible economic damage. A major problem, however, is that many insect parasites have a very narrow host range. This limits the usefulness of any given parasite species in biological control programs. In this paper we determined the influence of parasite venom on pest insect immune reactions to the parasite, showing that the venom is essential for success of the parasite. This research will be very useful to scientists who research host-parasite interactions. The information in this paper inform future research designed to fully understand how parasite venom can be used to broaden the host range of a parasite. Ultimately, this research will benefit growers who need to produce high quality vegetable crops and the people who consume safe and available vegetables.
Technical Abstract: A prophenoloxidase (PPO) cDNA (OfPPO) was cloned from the Asian corn borer Ostrinia furnacalis. Sequence analysis revealed a full length transcript of the OfPPO cDNA with 2686 bp, containing a 2079 bp open reading frame (ORF), a 73-bp 5’-untranslated region, and a 534-bp 3’-untranslated region with a poly(A) signal. The ORF encodes a 693-amino acid polypeptide, containing two distinct copper-binding regions, a plausible thiol ester site, two proteolytic activation sites, and a conserved C-terminal region, but lacks a signal peptide sequence. Temporal expression of the OfPPO transcript in the plasma, hemocytes, fat body and midgut was inhibited by Macrocentrus cingulum at 4 h post-parasitization (pp). In situ hybridization analysis showed that the hemocytes, especially the oenocytoids, hybridized strongly with the DNA probes of the OfPPO gene. No signal was detected in the cuticular epithelium or fat body of the parasitized larvae. Colloidal gold particles were used to visualize the PPO by immunoelectron microscopy. The time course study revealed a decrease in the labeling of the OfPPO at 4 h, 6 h, 8 h, 12 h and 1 day pp in the larval integument and midgut parasitized by M. cingulum. We infer from time course studies of OfPPO gene expression and PO enzymatic activity that OfPPO in the integument is transported from hemocytes and that the OfPPO expression was influenced at the transcriptional, translational and then the post-translational level sequentially by parasitization challenge.