Cp Kyriacou

A second timeless gene in Drosophila shares greater sequence similarity with mammalian tim

R.C. and C.P.K. were supported by grants from the European Community and CRUI-MURST-British Council, R.C. by grants from MURST-progetti nazionali and Ministero per le Politiche Agricole, and E.R. by a David Phillips Fellowship from BBSRC.

Genetic Divergence in the cacophony IVS6 Intron Among Five BrazilianPopulations of Lutzomyia longipalpis

Genes involved in the reproductive isolation are particularly useful as molecular markers in speciation studies. Lutzomyia longipalpis (Diptera: Psychodidae: Phlebotominae), a putative species complex, is a vector of visceral leishmaniasis in Latin America. We isolated from this species a fragment homologous to cacophony, a Drosophila gene that encodes features of the lovesong, an acoustic signal that is important in the sexual isolation of closely related species and known to vary considerably among L. longipalpis putative siblings species. Using an intron of the sandfly cacophony as a marker, we analyzed the molecular variation and sequence divergence among five populations of L. longipalpis from Brazil, three allopatric (Jacobina, Lapinha and Natal) and two putative sympatric sibling species from the locality of Sobral. A high level of polymorphism was found and analysis of the data indicates that very little gene flow is occurring among the populations of Jacobina, Lapinha, and Natal. A high level of differentiation was also observed between the two putative sympatric species of Sobral, one of which seems to be the same sibling species found in Natal, while the other is somewhat more related to Jacobina and Lapinha. However, the amount of estimated gene flow among the Sobral siblings is about seven times higher than the previously estimated for period, another lovesong gene, perhaps indicating that introgression might be affecting cacophony more than period. The results suggest that L. longipalpis is not a single species in Brazil, but it is yet not clear whether the different populations studied deserve species status rather than representing an incipient speciation process.

FEMALE SONG PREFERENCE AND THE PERIOD GENE IN DROSOPHILA

Mutations at theperiod (per) locus inDrosophila melanogaster alter rhythmic components of the male courtship song. We have examined the mating speed of females homozygous for mutantper alleles when presented with artificial mutant songs. Mutant females retain a preference for wild-type over mutant songs, thus male song and female preference are probably under separate genetic control. In contrast,per-mutant females from an established laboratory stock which had been maintained for nearly two decades appear to have an enhanced response to the corresponding mutant song in that they no longer discriminate against mutant song. These results are discussed in terms of the “genetic coupling” and “coevolution” theories of complementarity between male and female components of communication systems.

Drosophila courtship song cycles in normal and period mutant males revisited.

Courtship songs of normal males and those expressing short-period, long-period, and arrhythmic mutations at theperiod (per) locus ofDrosophila melanogaster have been reanalyzed for rhythmic components, using spectral treatments of the fluctuating rates of tone pulse production that occur during courtship. It was concluded, as in previous studies, that such songs are strongly rhythmic, except for courtships performed byper01 males. Songs produced by males expressing this and otherper alleles were compared to computer-generated “random” ones. Interpulse interval variations influenced byper01 and songs simulated to be arrhythmic both were found to be associated with cryptic rhythmicities; several such period values, extracted by the spectral analyses, defined very short cycle durations. We discuss the implications of these findings and of some recently reported results that have challenged the existence of rhythmicity inDrosophila songs.

Evolution of the threonine-glycine repeat region of the period gene in the melanogaster species subgroup of drosophila

SummaryThe Threonine-Glycine (Thr-Gly) region of the period gene (per) in Drosophila was compared in the eight species of the D. melanogaster subgroup. This region can be divided into a diverged variable-length segment which is flanked by more conserved sequences. The number of amino acids encoded in the variable-length region ranges from 40 in D. teissieri to 69 in D. mauritiana. This is similar to the range found within natural populations of D. melanogaster. It was possible to derive a Thr-Gly “allele” of one species from that of another by invoking hypothetical Thr-Gly intermediates. A phylogeny based on the more conserved flanking sequences was produced. The results highlighted some of the problems which are encountered when highly polymorphic genes are used to infer phylogenies of closely related species.

Molecular Evolution of the period Gene in Sandflies

The molecular evolution of the clock gene period was studied in Phlebotomine sandflies (Diptera: Psychodidae). Comparison of the synonymous and nonsynonymous substitution rates between sandflies and Drosophila revealed a significantly higher evolutionary rate in the latter in three of the four regions analyzed. The differences in rate were higher in the sequences flanking the Thr–Gly repetitive domain, a region that has expanded in Drosophila but remained stable and short in sandflies, a result consistent with the coevolutionary scenario proposed for this region of the gene. An initial phylogenetic analysis including eight neotropical sandfly species and one from the Old World was also carried out. The results showed that only the subgenus Nyssomyia is well supported by distance (neighbor-joining) and maximum parsimony analysis. The grouping of the other species from the subgenus Lutzomyia and Migonei group shows very low bootstrap values and is not entirely consistent with classical morphological systematics of the genus Lutzomyia.

Reproductive isolation and the period gene of Drosophila

The identification of genes of large effect on ecologically important traits is an important aim of molecular ecology. The period gene of Drosophila is a candidate for a gene with a large influence on premating isolation between Drosophila species, as it determines species specific aspects of courtship behaviour. Strains of D. melanogaster are available which have been genetically transformed with the period gene of either D. melanogaster or D. simulans. Here we show that D. melanogaster females do not discriminate between two such strains. This suggests that period may only make a small contribution to total premating isolation between these species. We discuss the use of genetically transformed strains in assessing the influence of single genes on complex traits.

Mutational mechanisms, phylogeny, and evolution of a repetitive region within a clock gene of Drosophila melanogaster.

TheD. melanogaster clock geneperiod (per) is an internally repetitive gene encoding a tandem array of Thr-Gly codons that are highly polymorphic in length in European natural populations. The two major length variants, (Thr-Gly)20 and (Thr-Gly)17, show a highly significant latitudinal cline. In this study we present the complete sequence of the Thr-Gly region of 91 individuals from 6 natural populations ofD. melanogaster, 5 from Europe and 1 from North Africa. We further characterized these 91 individuals for polymorphic sites in two other regions, one upstream and one downstream of the Thr-Gly repeat. We used the haplotypic combinations of Thr-Gly allele with flanking markers in an attempt to identify the mechanisms involved in the evolution of theD. melanogaster Thr-Gly region and to infer the phylogenetic relationship existing among the Thr-Gly alleles. We observe evidence for both intra- and interallelic mutational mechanisms, including replication slippage, unequal crossing-over, and gene conversion.

A cline in the Drosophila melanogaster period gene in Australia: neither down nor under

Weeks et al. (2006) have reported their inability to find a cline in the frequencies of the major Thr‐Gly encoding length variant alleles of the period gene in Drosophila melanogaster in Eastern Australia. This is in contrast to a study by Sawyer et al. (2006) , who found a cline on this continent from samples collected in 1993. Weeks et al. then cast doubt on the validity of a robust cline found for these variants in Europe by Costa et al. (1992) , criticizing their molecular techniques and sampling methods. We show how these claims are unjustified, and reveal a number of potential problems in their own methodology. Finally by reanalysing the subset of their data which they state is more reliable, we suggest that their results from Australia may be reasonably consistent with our own.

The Drosophila circadian clock going wild: PERIOD and TIMELESS oscillations under natural conditions

IS FOR TALKS