Genomic variants of a temperature-sensitive mutant of Autographa californica nuclear polyhedrosis virus containing specific reiterations of viral DNA.

Restriction endonuclease analysis of DNA from isolates of a temperature-sensitive mutant, ts.8, of Autographa californica nuclear polyhedrosis virus revealed the presence of genomic variants. ts8 type A plaque isolate DNA had altered restriction patterns while ts8 type B plaque isolate DNA restriction patterns were similar to wild-type viral DNA. The alterations in ts8 type A included an extra 1.35 kilobase pair (kbp) EcoRI fragment, and a series of extra Hind111 and XhoI restriction fragments present in decreasing molar ratios with increasing molecular weight.Southern blot and DNA-DNA cross-blot analysis indicated that the ts8A extra restriction fragments were homologous to viral sequences from the 90% region of the genome. The t&A extra restriction fragments appeared to result from an insertion of repeated viral DNA sequence at the EcoRI P-B junction. The higher molecular weight ts8A Hind111 and XhoI submolar fragments appeared to have increasing copy numbers of the 1.35 kbp EcoRI-EcoRI repeat-unit flanked by authentic EcoRI fragment P and B sequences. Approximately 57% of the ts8 plaques isolates analyzed were type A and 43% were type B genomic variants. Although type A and type B genomic variants appeared to be stable in high multiplicity of infection passage experiments, lo-20% of plaque isolates in stock homogeneity experiments converted from one type to another. The genomic alterations did not appear to have any observable effect on the temperature-sensitive phenotype of the mutant.