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Two Microplitis demolitor polydnavirus mRNAs expressed in hemocytes of Pseudoplusia includens contain a common
M R Strand1, R A Witherell, D Trudeau
1Department of Entomology, University of Wisconsin-Madison, 53706, USA. mstrand@calshp.cals.wisc.edu
Abstract:
Microplitis demolitor is a polydnavirus-carrying wasp that parasitizes the larval stage of Pseudoplusia includens. A previous study indicated that M. 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 kb) expressed in P. includens hemocytes that have homology to the viral genomic clone pMd-2. Corresponding 1.0- and 1.5-kb cDNA clones (MdPi455 and MdPi59) were isolated from an MdPDV-infected hemocyte cDNA library. Nucleotide sequence analysis of the cDNA clones confirmed 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 two introns and three exons 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 genomic DNA as is OMd1.0. The predicted peptide sequences for the 1.0- and 1.5-kb transcripts contain a cysteine-rich region at their 5' ends that have some similarity with epidermal growth factor-like motifs. Hybridization 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.
Insights
This study identifies two Microplitis demolitor polydnavirus (MdPDV) mRNAs in Pseudoplusia includens hemocytes. These viral transcripts are expressed in immune cells, potentially impacting the host
Area of Science:
- Insect pathology
- Virology
- Immunology
Background:
- Microplitis demolitor polydnavirus (MdPDV) infects Pseudoplusia includens hemocytes.
- MdPDV infection alters host immune responses, aiding parasitoid survival.
Purpose of the Study:
- Identify and characterize MdPDV mRNAs expressed in P. includens hemocytes.
- Investigate the origin and potential function of these viral transcripts.
Main Methods:
- Isolation of cDNA clones (MdPi455, MdPi59) from an MdPDV-infected hemocyte library.
- Nucleotide sequence analysis and alignment of viral mRNAs and genomic DNA.
- Hybridization studies to determine mRNA expression in hemocyte types.
Main Results:
- Two MdPDV mRNAs (1.0 and 1.5 kb) with homology to the viral genome were identified.
- The 1.0-kb mRNA is encoded by the OMd1.0 gene, while the 1.5-kb mRNA originates from a related gene.
- Both transcripts encode peptides with cysteine-rich regions similar to epidermal growth factor-like motifs.
- mRNAs are expressed in granular cells and plasmatocytes, key immune cells.
Conclusions:
- MdPDV expresses specific mRNAs within host hemocytes.
- These viral transcripts may play a role in modulating the host immune system.
- Understanding these viral genes is crucial for comprehending host-parasitoid interactions.