Evolution of the proportions of two sigma viral types in experimental populations of Drosophila melanogaster in the absence of the allele that is restrictive of viral multiplication.
A minority of flies in natural populations of Drosophila melanogaster are endemically infected by a rhabdovirus, sigma. The virus is vertically transmitted through male and female gametes. Two alleles of a fly locus, the ref(2)P locus, are present as a polymorphism in all populations: O permissive, and P restrictive for viral multiplication and transmission. Two viral types are known, Type I, which is very sensitive to the P allele, and Type II, which is more resistant. Previous observations have shown that, in presence of the P allele, viral Type II is selected for, in both natural and experimental populations. The aim of the present study was to determine whether, in the absence of P, Type I is selected for, or whether the two types are equivalent. For this purpose, experimental populations deprived of the P allele and differing in the initial proportions of the two viral types were established. After several generations, and despite a possible bias toward Type I, the frequencies of Type I and Type II clones differed in the various populations, depending on their initial values. These findings do not rule out selective advantage of viral Type I in the absence of P, but suggest that, if any, this advantage is in no way comparable to that displayed by viral Type II in the presence of P.
Fleuriet
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Equipe Génome Mitochondrial, Université Blaise Pascal, 63177 Aubière Cedex, France.
D000483:Alleles; D000818:Animals; D005075:Biological Evolution; D003001:Cloning, Molecular; D004331:Drosophila melanogaster / Q000235:genetics / Q000821:virology*; D005260:Female; D008297:Male; D012209:Rhabdoviridae / Q000235:genetics* / Q000502:physiology; D014779:Virus Replication / Q000235:genetics*