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Published on: October 6, 2017
Characterization of two novel Microplitis demolitor polydnavirus mRNAs expressed in Pseudoplusia includens haemocytes
D Trudeau1, R A Witherell1, M R Strand1
1Department of Entomology, University of Wisconsin-Madison, Madison, WI 53706, USA1.
Abstract:
The braconid wasp Microplitis demolitor carries M. demolitor polydnavirus (MdPDV) and parasitizes the larval stage of the moth Pseudoplusia includens. M. demolitor injects MdPDV into P. includens larvae when it lays an egg and the virus infects various cells including haemocytes. Two new MdPDV transcripts expressed in host haemocytes were characterized in this study. Screening of an MdPDV-infected haemocyte cDNA library identified a 0.4 kb cDNA encoding a predicted protein of 103 amino acids which was named Egf0. 4. This protein contained a cysteine-rich epidermal growth factor (EGF)-like motif at its N terminus that was similar to the EGF-like domains in the previously identified MdPDV genes egf1.5 and egf1.0. Sequencing of the genomic clone pMd-10 indicated that it contained the egf0.4 gene, which consisted of two introns and three exons. This gene was located on MdPDV segment O and appeared to exist in multiple copies. A nucleic acid and expression screen identified a 1. 8 kb cDNA encoding a predicted protein of 515 amino acids designated Glc1.8. This protein consisted of a heavily glycosylated central core of six tandemly arranged repeats flanked by hydrophobic N- and C-terminal domains. Northern blotting and in situ hybridization studies indicated that both egf0.4 and glc1.8 were expressed in MdPDV-infected host haemocytes. Immunocytochemical studies also indicated that Glc1.8 localized to the cell surface.
Insights
Two novel polydnavirus genes, egf0.4 and Glc1.8, were identified in the hemocytes of Pseudoplusia includens larvae parasitized by Microplitis demolitor. These genes are expressed within host hemocytes, contributing to the virus-host interaction.
Area of Science:
- Virology
- Insect Pathology
- Molecular Biology
Background:
- The braconid wasp *Microplitis demolitor* parasitizes *Pseudoplusia includens* larvae.
- This parasitism involves the injection of *M. demolitor* polydnavirus (MdPDV), which infects host hemocytes.
Purpose of the Study:
- To characterize novel MdPDV transcripts expressed in host hemocytes.
- To investigate the genetic structure and expression of these viral genes.
Main Methods:
- Screening of a hemocyte cDNA library to identify viral transcripts.
- Gene sequencing and analysis of genomic clones.
- Northern blotting and in situ hybridization for expression analysis.
- Immunocytochemistry to determine protein localization.
Main Results:
- Identification and characterization of a 0.4 kb cDNA encoding Egf0.4, containing an EGF-like motif.
- Identification and characterization of a 1.8 kb cDNA encoding Glc1.8, a heavily glycosylated protein.
- Both *egf0.4* and *glc1.8* genes were confirmed to be expressed in MdPDV-infected host hemocytes.
- Glc1.8 was localized to the host cell surface.
Conclusions:
- Two new MdPDV genes, *egf0.4* and *glc1.8*, are expressed in host hemocytes.
- These genes encode proteins with distinct structural features, including EGF-like motifs and glycosylation.
- The expression and localization of Glc1.8 suggest a role in virus-host interactions at the cell surface.
