Conserved Homologous Regions between Two Baculovirus DNAs

Regions of homology on the physical maps of Spodoptera exempta multiple-nucleocapsid nuclear polyhedrosis virus (SeMNPV-25), an Autographa californica MNPV genomic variant, and S. frugiperda (SfMNPV-2) baculovirus DNAs were identified by reciprocal DNA-DNA blot hybridization under conditions of an effective temperature of Tm -25 °C. In addition, cloned fragments of the viral genome which contained the homologous regions were used in hybridization experiments to confirm, refine and correlate the regions of the two physical maps. Five homologous regions conserved between the two physical maps were identified. When the stringency of the hybridization was increased (Tm -20 °C), only two of the original regions were identified by blot hybridization. One of the two regions contained the polyhedrin gene, and the other region was not associated with any known viral function. The five regions did not overlap with the intragenic homologous sequence (hr1 to hr5) regions on the SeMNPV-25 map or with restriction endonuclease variant (vI to vIV) regions on the SeMNPV-25 and SfMNPV-2 maps. The degree of similarity in the genomic organization of these two baculoviruses is discussed.