Role Of Venom And Ovarian Proteins In Immune Suppression Of Its Host Parasitized By Macrocentrus Cingulum

Macrocentrus cingulum, a polyembryonic wasp, can parasitize the larvae of Ostrinia furnacalis successfully. During ovipositing, M. cingulum oviposites venom, ovarian proteins as well as eggs and these active facts play an important role in escaping its host immune reaction. In this study we first observed the morphology and structure of the venom reservoir and ovary from M. cingulum and analyzed the components of venom and ovarian proteins. For further study, we focused on the effects of venom and ovarian proteins on spreading, viability and encapsulation of O. furnacalis hemocytes during parasitization.The results are as follows:1. Morphology and ultrastructure of the venom apparatus and ovary of endoparasitoid Macrocentrus cingulum Brischke (Hymenoptera: Braconidae) were observed by using light and electron transmission microscopes. The venom apparatus of M. cingulum was composed of one venom reservoir and two gland filaments. The gland filaments joined together at the top of the venom reservoir. The gland filaments consisted of an outer single layer of secretory cells, a layer of degenerated ectodermal cells and an inner intima lined the lumen. Secretory cells contained a distinct nucleus and a big vesicular organelle, which secreted the components of venom. The reservoir consisted of a muscular sheath and squamous cells, but no secretory cells. M. cingulum has a pair of ovaries and each one has approximately ten ovarioles connected with a lateral oviduct via a small calyx region. Two lateral oviducts formed a common oviduct and opened into the ovipositor. The venom apparatus joined together with the common oviduct by its venom duct.2. SDS– ployarylamide gel electrophoresis showed that there were seven proteins bands between 43-100 kDa in the venom from M. cingulum and the most abundant proteins were 97 kDa, 64 kDa, 45 kDa. Twelve proteins bands between 30-200 kDa were assayed by SDS-PAGE from the ovarian proteins and the most abundand proteins were 39 kDa and 43 kDa.3. The effects of venom from M. cingulum on Sephadex A-25 beads encapsulation of O. furnacalis hemocytes at 4 hours and 24 hours both in vitro and in vivo were assayed. The results showed that the venom from M. cingulum has no significant suppression on encapsulation of hemocytes. At the same condition and treatments, venom didn't suppress the spreading and viability of O. furnacalis hemocytes at 4 hours and 24 hours both in vitro and in vivo.4. The effects of ovarian proteins from M. cingulum on Sephadex A-25 beads encapsulation of O. furnacalis hemocytes at 4 hours and 24 hours both in vitro and in vivo were assayed. The results showed that the ovarian proteins significantly suppress the encapsulation of O. furnacalis hemocytes and this suppression of ovarian proteins was concentration-depended. At the same condition and treatments, ovarian proteins from M. cingulum hadn't significant suppression on spreading and viability of O. furnacalis hemocytes. These results revealed that ovarian proteins from M. cingulum suppressed the encapsulation of O. furnacalis hemocytes and may play an important role in escaping its host immune reaction. By comparing the effects of ovarian proteins and mixture (ovarian proteins and venom) from M. cingulum on encapsulation of O. furnacalis hemocytes, the results showed that the two treatments hadn't significant difference. It revealed that venom hadn't synergy with ovarian proteins during suppressing the encapsulation of O. furnacalis hemocytes.