title: Sequence variation in couch potato and its effects on life-history traits in a northern malt fly, Drosophila montana.
abstract: Couch potato (cpo) has previously been connected to reproductive diapause in several insect species including Drosophila melanogaster, where it has been suggested to provide a link between the insulin signalling pathway and the hormonal control of diapause. In the first part of the study we sequenced nearly 3.6 kb of this gene in a northern Drosophila species (Drosophila montana) with a robust photoperiodically determined diapause and found several types of polymorphisms along the sequenced area. We also found variation among five Drosophila virilis group species in the length of the 5th exon of cpo and in the site of the stop codon at the end of this exon. The second part of the study was targeted on a deletion of six amino acids located in the last section of exon 5, which in D. melanogaster, is translated only in one short transcript lacking the following exons. The studied deletion appeared to be extremely rare in the wild D. montana population where it was found, but its frequency rapidly increased during laboratory culture. qPCR analyses showed the expression level of the deletion allele to be significantly downregulated in both the diapausing and non-diapausing females compared to the wild type allele. At the phenotypic level, the deletion and the decreased expression of cpo transcript involving it did not have direct effect on the incidence of female reproductive diapause, but it was associated with a reduction in development time under diapause-inducing conditions. This suggests that while the cpo transcript containing the prolonged version of the 5th exon with a stop codon is clearly associated with fly development time, the exons with RNA domains included in other transcripts of the gene may be more directly related to diapause regulation.
authors.affiliation: Centre of Excellence in Evolutionary Research, Department of Biological and Environmental Science, P.O. Box 35, 40014 University of Jyväskylä, Finland. maaria.kankare@jyu.fi
authors.forename: Maaria
authors.initials: M
authors.lastname: Kankare
authors.forename: Tiina S
authors.initials: TS
authors.lastname: Salminen
authors.forename: Hanna
authors.initials: H
authors.lastname: Lampinen
authors.forename: Anneli
authors.initials: A
authors.lastname: Hoikkala
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D017124:Conserved Sequence; D004330:Drosophila / Q000235:genetics* / Q000254:growth & development; D029721:Drosophila Proteins / Q000235:genetics*; D005091:Exons; D005260:Female; D007438:Introns; D008297:Male; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics*; D010641:Phenotype; D011110:Polymorphism, Genetic; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity
chemical_list: D029721:Drosophila Proteins; D009687:Nuclear Proteins; C078019:cpo protein, Drosophila