PHENOTYPIC AND GENETIC-ANALYSIS OF LYMANTRIA-DISPAR NUCLEOPOLYHEDROVIRUS FEW POLYHEDRA MUTANTS - MUTATIONS IN THE 25K FP GENE MAY BE CAUSEDBY DNA-REPLICATION ERRORS
Ds. Bischoff et Jm. Slavicek, PHENOTYPIC AND GENETIC-ANALYSIS OF LYMANTRIA-DISPAR NUCLEOPOLYHEDROVIRUS FEW POLYHEDRA MUTANTS - MUTATIONS IN THE 25K FP GENE MAY BE CAUSEDBY DNA-REPLICATION ERRORS, Journal of virology, 71(2), 1997, pp. 1097-1106
We previously demonstrated that polyhedron formation (PF) mutants aris
e at a high frequency during serial passage of the Lymantria dispar nu
cleopolyhedrovirus (LdMNPV) in the L. dispar 652Y cell line (J. M. Sla
vicek, N. Hayes-Plazolles, and M. E. Kelly, Biol. Control 5:251-261, 1
995). Most of these PF mutants exhibited the traits of few polyhedra (
FP) mutants; however, no large DNA insertions or deletions that correl
ated with the appearance of the FP phenotype were found, In this study
, we have characterized several of the PF mutants at the phenotypic an
d genetic levels, Genetic techniques were used to group the mutations
in the LdMNPV PF mutants to the same or closely linked genes, Wild-typ
e viruses were recovered after coinfection of L. dispar 652Y cells wit
h certain combinations of PF mutants, These viruses were analyzed by r
estriction endonuclease analysis and found to be chimeras of the origi
nal PF mutants used in the coinfections. Marker rescue experiments loc
alized the mutations in one group of PF isolates to the region contain
ing the LdMNPV 25K FP gene, The mutations in these PF mutants mere ide
ntified, Four of five of the LdMNPV FP mutants contain small insertion
s or deletions within the 25K FP gene. The fifth LdMNPV FP mutant anal
yzed contained a large deletion that truncated the C terminus of the 2
5K FP gene product, All of the deletions occurred within the same pote
ntial hairpin loop structure, which had the lowest free energy value (
most stable hairpin) of the five potential hairpin loop structures pre
sent in the 25K FP gene, One of the insertion mutants contained an ext
ra base within a repetitive sequence, These types of mutations are lik
ely caused by errors that occur during DNA replication. The relationsh
ip between the types of mutations found within the LdMNPV 25K FP gene
and DNA replication-based mutagenesis is discussed.