Summary auto-generated
This study describes the first cell lines established from the ichneumonid wasp Hyposoter didymator, a parasitoid wasp that carries an integrated polydnavirus called H. didymator ichnovirus (HdIV). Four cell lines—designated Hd-AA, Hd-AD, Hd-BBA, and Hd-K—were derived from wasp pupae after approximately two years in culture. PCR analysis of 18S ribosomal DNA confirmed the wasp origin of all cell lines, excluding contamination from the lepidopteran host Spodoptera littoralis. Southern blot analysis revealed that viral DNA was present and integrated into wasp chromosomes in all four lines. Northern blot analysis of the AA cell line detected low-level transcription of some HdIV genes. The four cell lines exhibited distinct morphologies and growth rates, ranging from 2 to 8 days doubling time. When the AA cell line was treated with ecdysone, reinfected with HdIV, or exposed to heat shock at 42°C, no detectable virus replication or increased gene expression occurred. These cell lines represent valuable tools for investigating polydnavirus biology, genome organization, and replication mechanisms in wasp hosts, though the regulation of viral replication remains incompletely understood.
Key findings
- First cell lines established from a polydnavirus-associated wasp, derived from Hyposoter didymator pupae and maintained successfully in culture for multiple passages
- Integrated viral DNA present in all four cell lines and co-localized with high molecular mass wasp chromosomal DNA, confirmed by Southern blot analysis
- Low-level transcription of some HdIV genes detected in AA cell line, but neither ecdysone treatment, viral reinfection, nor heat shock induced detectable virus replication
- Cell lines displayed polyploidization and distinct morphological characteristics including variations in cell shape, growth rates, and intercellular junction formation
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Abstract
Cell lines derived from polydnavirus-associated wasps should constitute a valuable tool for investigations of polydnavirus replication, but none is yet available. In this work, we describe the first cell lines, named Hd-AA, -AD, -BBA and -K, to have been established from the ichneumonid wasp Hyposoter didymator, associated with the polydnavirus H. didymator ichnovirus (HdIV). Southern blot analysis indicated that the viral DNA was present in all four cell lines and co-localized with high molecular mass DNA, probably the wasp chromosomes. Northern blot analysis of mRNAs extracted from the AA cell line showed transcription of some HdIV-encoded genes, although at low level. The effects of ecdysone treatment, HdIV re-infection and 42 °C heat-shock were analysed in the AA cell line. No effect was detected at the DNA (virus replication) or RNA (gene expression) levels, which may be due to the limitation of the present available tools.