Organization of polygenic systems: Cell death modifiers from natural populations ofDrosophila melanogaster

Abstract

SUMMARYExpression of three wing-cell death mutants inDrosophilamelanogaster was used to survey cryptic polygenic modifiers of cell death in wild type strains. Females carrying the X-linked mutants Beadex-3, notchoid and scalloped were crossed to males from each of 20 isofemale strains. Phenotypic variation in the amount of cell death was measured in F1mutant males that were heterozygous for polygenic loci segregating in the wild strains. As expected, each mutant uncovered a broad range of polygenic variation among strains. Yet, when cluster analyses were used to evaluate the degree of correlation among the expressions ofBx3,sdandnd, the isofemale strains could be partitioned into a small number of groups that were similar in the effects they had upon the severity of cell death. Chromosome mapping of one cell death suppressor strain demonstrated that different polygenic loci could produce the same phenotype in different mutant backgrounds.