Phenotypic plasticity of abdominal pigmentation in Drosophila kikkawai: multiple interactions between a major gene, sex, abdomen segment and growth temperature.
Drosophila kikkawai is known to be polymorphic for a single autosomal locus controlling abdomen pigmentation in females. Two strains homozygous at this locus (Abdomen pigmentation, Abp) were established from a polymorphic Indian population: one was homozygous (DD) for the dark allele, the other (LL) for the light allele. A Mendelian analysis of crosses at 25 degrees C confirmed the occurrence of a major locus, with dominance of the D allele. Phenotypic variation of pigmentation according to growth temperature was then analyzed in DD and LL male and female flies, and in reciprocal F1. A slight difference was found between reciprocal F1--females from a dark mother were darker but not at all temperatures. In females, the D allele exhibited an antero-posterior gradient of increasing expression from segment 2-7, with dominance over L and an increased expression at low temperatures. In males, abdomen pigmentation was uniformly light in segments 2-5, the D allele being repressed by the sex genotype. In segment 6, the D allele was expressed but only at low temperatures, and was either recessive to L or codominant. Phenotypic plasticity that is, amount of change induced by different growth temperatures, was variable according to genotype and segment. It always corresponded to a darkening of the fly at lower temperatures, but was generally much less than in D. melanogaster. In D. kikkawai, climatic adaptation might occur more by changing the frequency of the D allele than by phenotypic plasticity.
Gibert
P
P
Laboratoire Populations, Génétique et Evolution, CNRS 91198 Gif sur Yvette, France.
Moreteau
B
B
Munjal
A
A
David
J R
JR
D000005:Abdomen / Q000033:anatomy & histology*; D000818:Animals; D004330:Drosophila / Q000235:genetics* / Q000254:growth & development; D005260:Female; D008297:Male; D010641:Phenotype; D010858:Pigmentation / Q000235:genetics*; D012737:Sex Factors; D013696:Temperature