Abstract
Three temperature-sensitive (ts) mutants of Bombyx mori nucleopolyhedrovirus (BmNPV), designated as ts-S2, ts-S3, and ts-S4, were isolated, based on a lack of or reduced polyhedra production at a non-permissive temperature of 33°C. Each mutant was characterized at a permissive temperature of 25°C and at 33°C, and at a dose of 7.2 TCID50/cell. Viral DNA synthesis in BmN4 cells infected with ts-S2 was defective at 33°C, but partially defective at this temperature in BmN4 cells infected with ts-S3 and ts-S4. Production of budded virus and polyhedrin synthesis in cells infected with ts-S2 were severely diminished at 33°C, but only slightly reduced in cells infected with ts-S3. For ts-S4, production of budded virus was partially defective and polyhedrin synthesis was completely defective at 33°C. These distinct phenotypes among the 3 ts mutants were complementary to each other in recovering the wild-type characteristics in culture when BmN4 cells were coinfected with a pair of ts mutants, demonstrating that these were distinct ts mutations. Marker rescue tests to identify ts mutations of the mutants showed that ts-S2 possessed a ts mutation within an ORF for a putative DNA helicase gene, and both ts-S3 and ts-S4 possessed multiple ts mutations in separate regions of the genomes.
