Analysis of species specificity in endoparasitoids

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Larval endoparasitoids have to regulate the host in the physiological condition to acquire the suitable state for the development of their eggs and larvae. Between two different parasitoids being able to attack the same host species (Pseudaletia separata), one parasitoid, Cotesia ruficrus is restricted to parasitize the young stadium of the host, while another parasitoid, Cotesia kariyai is able to parasitize successfully through all stadium. Reciprocal exchanging of the polydnavirus and the venom of each parasitoid produced the host regulation according to the characteristics of the polydnavirus. Each genomic DNA segments hybridized with the reciprocal genornic DNA segments of PDV.Furthermore, we reported the cloning and characterization of Cotesia kariyai polydnavirus (CkPV) genes expressed in host Pseudaletia separata testes. We isolated clones encoding CkPV mRNAs from a cDNA library of host testes. We found two motif sequences of the RNase T_2 family in one of CkPV gene expressed in host testes. The CkPV RNase T_2 fragment was hybridized to more than one viral genome segments. By northern blot analysis using cloned CkPV RNase T_2 gene as a probe, we showed the 3.1 kbp and 2.3 kbp mRNAs were detected 4-12h after parasitization, which Was before the appearance of cells with abnormal chromatin in the host testes.