2 MICROPLITIS-DEMOLITOR POLYDNAVIRUS MESSENGER-RNA EXPRESSED IN HEMOCYTES OF PSEUDOPLUSIA-INCLUDENS CONTAIN A COMMON CYSTEINE-RICH DOMAIN

Microplitis demolitor is a polydnavirus-carrying wasp that parasitizes the larval stage of Pseudoplusia includens. A previous study indicate d that ICI. demolitor polydnavirus (MdPDV) infects primarily hemocytes in parasitized hosts. Thereafter, several alterations that compromise the immune response of P. includens toward the developing parasitoid occur in hemocytes. In this study, we identified two MdPDV mRNAs (1.0 and 1.5 kh) expressed in P. includens hemocytes that have homology; to the viral genomic clone pMd-2. Corresponding 1.0- and 1.5-kb cDNA clo nes (MdPi455 and MdPi59) were isolated from an MdPDV-infected hemocyte cDNA library. Nucleotide sequence analysis of the cDNA clones confirm ed that the 1.5- and 1.0-kb mRNAs have significant regions of homology . Sequence alignment revealed that the gene, OMd1.0, encoding the 1.0- kb mRNA is present in pMd-2. This gene contains mo introns and three e xons that agree with the sequence for MdPi455. In contrast, the 1.5-kb mRNA is likely encoded by a related gene located on the same MdPDV ge nomic DNA as is OMd1.0. The predicted peptide sequences for the 1.0- a nd 1.5 kb transcripts contain a cysteine-rich region at their 5' ends that have some similarity with epidermal growth factor-like motifs. Hy bridization studies revealed that both mRNAs are expressed in granular cells and plasmatocytes, the primary classes of hemocytes involved in defense against M. demolitor and other parasites.