Pupation site preference selection in Drosophila jambulina

Larvae of Drosophila jambulina belonging to montium subgroup were tested for pupation site preference in relation to temperature. At higher temperature (30 °C), larvae preferred to pupate on food whereas at lower temperature (21 °C) pupation occurred on the cotton. Genetic basis of larval pupation behavior was studied by conducting reciprocal crosses for 30 generations on food-selected and on cotton-selected larvae. Results from genetic analysis between food-selected and cotton-selected strains suggested a single gene responsible for the pupation site preference, with F1 progeny pupated on cotton and F2 (F1×;F1) larvae pupated on both food as well on cotton. Although we found no change in morphological traits in food vs. cotton selected population, significantly different growth rate (body weight) between the two strains was observed. These results suggest that pupation site preferences can affect life-history traits in D. jambulina.

Drosophila bunnanda-a new species from northern Australia with notes on other Australian members of the montium subgroup (Diptera: Drosophilidae)

An unknown Drosophila montium subgroup species was collected on Cape York Peninsula in 1992, a live culture of the same species was established from flies collected in the vicinity of Lake Placid near Cairns in 2001. From these specimens we now have sufficient information to describe a new species—Drosophila bunnanda. It differs morphologically from the four other montium subgroup species already known from northern Queensland—D. serrata, D. birchii, D. kikkawai, and D. sp. cf. jambulina, and from one very similar species—D. dominicana—known from Papua New Guinea. Molecular data support the taxonomic findings. Additional information and a key for all Australian montium subgroup species is provided to allow clear differentiation between them and D. bunnanda.

A cluster of diagnostic Hsp68 amino acid sites that are identified in Drosophila from the melanogaster species group are concentrated around β-sheet residues involved with substrate binding

The coding region of the hsp68 gene has been amplified, cloned, and sequenced from 10 Drosophila species, 5 from the melanogaster subgroup and 5 from the montium subgroup. When the predicted amino acid sequences are compared with available Hsp70 sequences, patterns of conservation suggest that the C-terminal region should be subdivided according to predominant secondary structure. Conservation levels between Hsp68 and Hsp70 proteins were high in the N-terminal ATPase and adjacent β-sheet domains, medium in the α-helix domain, and low in the C-terminal mobile domain (78%, 72%, 41%, and 21% identity, respectively). A number of amino acid sites were found to be "diagnostic" for Hsp68 (28 of ~635 residues). A few of these occur in the ATPase domain (385 residues) but most (75%) are concentrated in the β-sheet and α-helix domains (34% of the protein) with none in the short mobile domain. Five of the diagnostic sites in the β-sheet domain are clustered around, but not coincident with, functional sites known to be involved in substrate binding. Nearly all of the Hsp70 family length variation occurs in the mobile domain. Within montium subgroup species, 2 nearly identical hsp68 PCR products that differed in length are either different alleles or products of an ancestral hsp68 duplication.Key words: Hsp70, Hsp68, diagnostic sites, Drosophila melanogaster, montium subgroup.

Isolation, characterization, and localization of β-tubulin genomic clones of three Drosophila montium subgroup species

Genomic libraries were constructed from three Drosophila species, namely Drosophila auraria, Drosophila serrata, and Drosophila kikkawai, belonging to the Drosophila montium subgroup of the Drosophila melanogaster species group. Clones containing β-tubulin specific sequences were isolated, characterized by restriction endonuclease digestions and Southern hybridizations, and mapped by in situ hybridization on the polytene chromosomes of the species studied. The distribution of the β-tubulin loci was found to be similar in D. montium species and D. melanogaster.Key words: genomic clones, β-tubulin, gene family, evolution, Drosophila montium subgroup.

The organization of the α-tubulin gene family in the Drosophila montium subgroup of the melanogaster species group

The α 1-, α 2-, α 3-, and α 4-tubulin genes have been mapped by in situ hybridization to the polytene chromosomes of five species representative of the Drosophila montium subgroup geographical distribution. A lambda phage clone containing α 1-tubulin specific sequences was isolated from a genomic DNA library of Drosophila auraria and its restriction endonuclease pattern is presented. Both well-characterized heterologous and homologous probes were used to assess orthogonality of gene members between species groups. The in situ hybridization pattern observed in all species studied is consistent with that of Drosophila melanogaster, since α 1-, α 2-, and α 3-tubulin genes are located on the same polytene arm, and the α 4-tubulin gene is found on a different arm. Cross-hybridization was observed among α 1-, α 2-, and α 3-tubulin specific sequences in all species studied, using either heterologous or homologous probes. However, unlike D. melanogaster, in all montium species studied, both α 1- and α 3-tubulin specific probes hybridize to the same polytene band, indicating a clustered organization of the above genes. The chromosomal organization of this gene family would suggest that taxa within the montium subgroup are closer to their common ancestor than are the taxa in the melanogaster species group. A mode of evolution for this gene family in Drosophila is proposed. Key words: α -tubulin genes, evolution, gene cluster, gene dispersion, Drosophila montium subgroup.