Differential infectivity of two Autographa californica nucleopolyhedrovirus mutants on three permissive cell lines is the result of lef-7 deletion.
We isolated two Autographa californica nucleopolyhedrovirus (AcMNPV) mutants that have infectivity similar to that of wild-type (wt) AcMNPV in TN368 cells, but reduced budded virus and polyhedral inclusion body production in IPLB-SF-21 and SE1c cells. Restriction endonuclease analysis and sequence analysis indicated that 3.2-kb (77.0-79.4 m.u.) and 4.4-kb (76.7-80.1 m.u.) regions, the location of four major open reading frames (ORFs), pk2, ORF-247, lef-7, and chitinase, were deleted in mutant T295 and T297, respectively. Phenotypes of recombinant viruses vdel-AG, in which all four ORFs were deleted, and vlef7-AG, in which only lef-7 was deleted, were identical to the mutants. The phenotypes of recombinant viruses with deletions of the other ORFs were indistinguishable from wt AcMNPV. This demonstrated that the deletion of lef-7 was responsible for the mutant phenotypes. Viral DNA synthesis in both mutant- and vlef7-AG-infected SF-21 and SE1c cells was reduced to less than 10% of that of wt AcMNPV-infected cells. In TN368 cells, DNA synthesis in mutant- and vlef7-AG-infected cells was delayed relative to wt-infected cells. Although lef-7 is not essential for AcMNPV infection in TN368 cells, it is expressed in TN368, SF-21, and SE1c cells in a similar manner.
Chen
C J
CJ
Program in Genetics, Michigan State University, East Lansing, Michigan, 48824-1115, USA.
Thiem
S M
SM
D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D002874:Chromosome Mapping; D017353:Gene Deletion; D017924:Nucleopolyhedroviruses / Q000235:genetics / Q000472:pathogenicity*; D011995:Recombination, Genetic; D018411:Spodoptera; D014764:Viral Proteins / Q000235:genetics* / Q000502:physiology; D014779:Virus Replication / Q000235:genetics
D014764:Viral Proteins; C087084:late expression factor 7, baculovirus