Genetic studies of mei-P26 reveal a link between the processes that control germ cell proliferation in both sexes and those that control meiotic exchange in Drosophila

We present the cloning and characterization of,mei-P26, a novel P-element-i nduced exchange-defective female meiotic mutant ill Drosophila melanogaster . Meiotic exchange in females homozygous for mei-P26' is reduced in a polar fashion, such that distal chromosomal legions are the most severely affect ed. Additional alleles generated by! duplication of the P element reveal th ;it mei-P26 is also necessary for germline differentiation in both females and males. To further assess the role of mei-P26 in germline differentiatio n, we tested double mutant combinations of,mei-P26 and bag-of-marbles (bam) , a gene necessary for the control of germline differentiation and prolifer ation in both sexes. A null mutation at the bam locus was found to act as a dominant enhancer of mei-P26 in both males and females. Interestingly, mei otic exchange in mei-P26'; bam(Delta 86)/+ females is also severely decreas ed in comparison to mei-P26' homozygotes, indicating that bam affects the m eiotic phc not!:pe as well. These data suggest that the pathways controllin g germline differentiation and meiotic exchange are related and that factor s involved in the mitotic divisions of the germline may regulate meiotic re combination.