Isolation, Complementation, and Initial Characterization of Temperature-Sensitive Mutants of the Baculovirus...

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 degrees C). At 32.5 degrees 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 degrees C. One mutant was defective in plaque formation, progeny nonoccluded virus formation, and polyhedra formation at 32.5 degrees C. Several mutants produced nonoccluded virus but failed to produce plaques or polyhedra at 32.5 degrees 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 degrees 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.