Isolation, Complementation, and Initial Characterization of Temperature-Sensitive Mutants of the Baculovirus Autographa californica Nuclear Polyhedrosis Virus

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Abstract
Sixteen temperature-sensitive mutants of Autographa californica nuclear polyhedrosis virus were isolated. Several interesting phenotypes were observed. A large proportion of the mutants were unable to form polyhedral occlusion bodies (polyhedra) at the nonpermissive temperature (32.5°C). At 32.5°C, one mutant formed plaques in which the cells lacked polyhedra. Another mutant type was defective in the production of progeny extracellular nonoccluded virus and produced a “plaque” consisting of only a single cell containing polyhedra at 32.5°C. One mutant was defective in plaque formation, progeny nonoccluded virus formation, and polyhedra formation at 32.5°C. Several mutants produced nonoccluded virus but failed to produce plaques or polyhedra at 32.5°C. Other phenotypes were also distinguished. Complementation analyses, performed by either measuring the increase in extracellular nonoccluded virus formation or by observing polyhedra formation in mixed infections at 32.5°C, indicated the presence of 15 complementation groups. A high frequency of recombination was observed. Four of the mutants were found to be host dependent in their temperature sensitivity for polyhedra formation.