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Title: Larval stage Lymantria dispar microRNAs differentially expressed in response to parasitization by Glyptapanteles flavicoxis parasitoid

item Gundersen-Rindal, Dawn
item Pedroni, Monica

Submitted to: Archives of Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/3/2010
Publication Date: 3/23/2010
Citation: Gundersen, D.E., Pedroni, M.J. 2010. Larval stage Lymantria dispar microRNAs differentially expressed in response to parasitization by Glyptapanteles flavicoxis parasitoid. Archives of Virology. 155:783-787.

Interpretive Summary: Parasitic wasps have great potential for the control of moth species that are pests of agricultural crops and forests. The wasps possess a virus, called a polydnavirus, which is injected with other factors into pest caterpillars during parasitism. In the current paper, we used modern molecular techniques to analyze for the first time unique small regulatory molecules, called microRNAs (miRNAs), which may be regulators of changes in the caterpillar in response to parasitism and injection of the polydnavirus by the wasp. We found several unique insect and virus miRNAs at high levels or low levels in the caterpillar pest hemolymph (insect blood) and identified certain miRNAs that are found in some caterpillar pest tissue types and not in others. This is the first time researchers have ever examined miRNA in gypsy moth caterpillars and many new findings were made. The information obtained will help explain how the wasp causes the decline of the pest caterpillar and may enable new biocontrol strategies based on wasp disruption of insect pest immune and other important systems. This information will be of interest to university and industry scientists who are interested in how viruses work and/or in developing new virus-based strategies to control pests.

Technical Abstract: MicroRNAs (miRNAs) are small RNA molecules that regulate gene expression by targeting messenger RNAs (mRNAs) and causing mRNA cleavage or blockage of translational. MiRNAs have never been examined in relation to parasitism of a lepidopteran host by a parasitic wasp possessing a symbiotic polydnavirus. Yet, this biological system is characterized by a high level of viral and host gene activity leading to immune suppression, developmental arrest, and other significant effects in the host. In this study, miRNA profiling of parasitoid wasp Glyptapanteles flavicoxis-parasitized Lymantria dispar (gypsy moth) larval hemocytes through microarray hybridization to known mature insect and virus miRNAs identified several differentially expressed miRNAs. Twenty-seven known insect and virus miRNA species were differentially expressed with statistical significance in G. flavicoxis-parasitized versus non-parasitized larvae, with a greater number overexpressed than underexpressed. These findings were confirmed by real-time relative quantitative PCR for selected insect miRNAs using miRNA-specific TaqMan™ assays. Of these, several examined showed differential expression patterns in diverse larval host tissues, including L. dispar mir-277, a miRNA that may be developmentally linked. Given this differential and tissue-specific expression, miRNAs may play an important role in regulation of pathogenesis and the aberrant gene expression associated with parasitism and introduction of polydnavirus in the lepidopteran host. Identification of parasitism-associated differentially regulated miRNAs in L. dispar provides a basis for future functional studies.