Host-specific transcription of nucleopolyhedrovirus gene homologues in productive and abortive Anticarsia gemmatalis MNPV infections

Summary

In a previous report, we showed that Anticarsia gemmatalis nucleo- polyhedrovirus (AgMNPV) infections of Choristoneura fumiferana IPRI-CF-124T and Bombyx mori BM-5 cell lines are abortive, whereas A. gemmatalis UFL-AG-286 cells efficiently produce infectious virus and polyhedral inclusion bodies (PIBs). In the present study, we explored transcription patterns in these infections using representative temporal classes of Autographa californica MNPV (AcMNPV) genes. Northern analyses were carried out using internal fragments of AcMNPV genes that hybridized strongly with AgMNPV genomic DNA. The results showed that ie-1(immediate-early) homologue, but not dnapol (delayed-early) homologue of AgMNPV was transcribed efficiently in the abortive infections. Transcription of gp67 (late) and polh (very late) homologues was minimal in C. fumiferana cells and undetectable in B. mori cells. Transcription patterns in AgMNPV-infected A. gemmatalis cells were similar to those reported for productive AcMNPV infections. These data are consistent with our previous observation that early cytopathic effect, but not infectious virus or PIBs are detected in abortive infections with AgMNPV. Our results suggest that C. fumiferana and B. mori cells restrict AgMNPV infections at the transcriptional level and that this block likely occurs between immediate-early and delayed-early phases of the NPV cycle. Our data do not preclude the possibility of additional restrictions at other stages.