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Poster Full Abstracts - Evolution and Quantitative Genetics
Poster board number is above title. The first author is the presenter
252
445A
Comparative studies of chromosomes of the tripunctata Species Group of Drosophila.
Mitsue Taukeuti Brianti, Galina Ananina, Louis Bernad Klaczko.
Universidade Estadual de Campinas, Campinas, São Paulo, Brazil.
In this work, we present detailed photomaps of the polytene chromosomes of five closely related species of the tripunctata group: Drosophila
mediopunctata, D. roehrae, D. unipunctata, D. paraguayensis and D. mediosignata. The tripunctata group (Drosophila subgenus) comprises 79 species, being
one of the largest Neotropical groups of species, second only to the repleta group. The tripunctata group with the groups: calloptera, cardini, guaramunu,
guarani, macroptera, pallidipenis, rubifrons and sticta, form the tripunctata radiation. This work is pioneering in detailed study of chromosomes of this
radiation species. We also analyzed the configurations of metaphase karyotypes of the five species. Moreover, using probes of genes from Drosophila
melanogaster, we identified Muller’s elements by fluorescence in situ hybridization (FISH), obtaining reliable evidence of homology for the chromosomes.
Furthermore, we characterized the inversion polymorphisms found in the strains of this species. When we analyzed chromosomal settings, noticed that D.
unipunctata karyotype presents a unique conformation showing an extra mitotic chromosome, which does not polytenize; and a pericentric inversion in the X
chromosome, suggesting a very fast chromosomal evolution. We also found a pattern for the distribution of chromosomal inversion polymorphisms among
Muller’s elements in these species. Element E is the most polymorphic, with many inversions in each species. Element C is the second most polymorphic; B
and D are the least polymorphic elements among the studied chromosomes. When we analyzed the distribution of chromosomal inversion polymorphisms
noticed a tendency of linkage disequilibrium between arrangements of chromosomal inversions located in the regions distal and proximal of the E in all
species analyzed. These results may be more general and are consistent with bibliographic data available for at least the subgenus.
446B
Deciphering B chromosome sequence of
Drosophila albomicans
by short-read sequencing.
Li Zhao
1,2
, Yue Zhang
2
, Qi Zhou
2
, Ruoping Zhao
2
, Wen
Wang
2
. 1) Department of Ecology and Evolution, University of California - Davis, Davis, CA; 2) CAS-Max Planck Junior Research Group, Kunming
Institute of Zoology, Chinese Academy of Sciences, Kunming, China.
B chromosomes are extra chromosomes in autosomal karyotype with considerable instability in their existence, number and structure, it doesn’t obey the
Mendelian inheritance laws, thus is of great significance for genetics. However, little is known about the DNA sequences of B chromosomes and their
transmission, origination and evolution. Here we use
Drosophila albomicans
as material to study this question.
D. albomicans
is the only species with B
chromosomes in
D. immigrans
group. Using the next generation Illumina sequencing technology, we sequenced the genome of the male flies of strains with
B chromosomes and the inbred female flies without B chromosomes but derived from the same strain. After filtering and mapping of the raw reads, we
compared assembled male genome sequence with the female sequence and successfully identified a B-link SNP site in a candidate B chromosomal scaffold
in which more than 20% B specific sequences were repetitive. Moreover, we collected about 1500 B chromosomes using microdissection technology, and
amplified these chromosomes’ DNA with linear amplification technique and sequenced the DNA by Illumina. A total 5,161,496 bp of scaffold was obtained
and was aligned with the assembled whole genome sequence data of
D. albomicans
to screen B chromosome specific DNA. We compared the B
chromosome assembling result with genome assembling sequences, and found that 0.55 MB chromosome sequences could blast to 1.6 M genome sequences.
Finally, part of B chromosome sequence, mostly rDNA, were assembled again using B chromosome sequencing reads which are overlap with the genome
sequencing reads, and supposed to be the B chromosome specific DNA. These B chromosome-specific sequences are all turned out to be rDNA localized in
the X heterochromatin region or unmapped heterochromatin region, indicating that B chromosomes sequences are homologous to those of A chromosomes
and B chromosome may partially originate from ancestor X chromosome.
447C
Characterization of the RNase T2 gene from
Drosophila melanogaster
and the evolution of this RNase family in protosomes.
Linda Ambrosio, Ryan
Bailey, Stephanie Moriss, Gustavo MacIntosh. Department of Biochemistry, Biophysics and Molecular Biology, Iowa State Univ, Ames, IA.
Ribonucleases of the T2 family are RNA degrading enzymes present in almost all eukaryotic organisms. The T2 RNases have been studied extensively in
plants, but their role in animals is relatively unknown. Several of the biological functions fulfilled by RNase T2 proteins in plants seem to be carried out by
members of a different RNase family, RNase A, in vertebrates. In zebrafish two RNase T2 paralogs have been identified with
rnaset2
implicated in
lysosomal degradation of rRNA. In order to further understand the role of T2 RNases in animals, phylogenetic analyses and studies of gene expression were
initiated in
D. melanogaster
. Only one gene of the T2 family,
RNaseX25
was identified in the Drosophila genome. We found that this gene was expressed in
all life cycle stages examined, supporting the hypothesis that the T2 RNase enzyme may have a housekeeping function in flies. However, preliminary gene
expression data suggest that
RNaseX25
may also be involved in different stress responses. Additionally, we used phylogenetic analysis to shed light on the
evolution of the T2 family of ribonucleases in protostomes. Only one gene, absolutely conserved, is found for most of these animal genomes. Together with
its ubiquitous expression, this conservation is consistent with a role for RNase T2 enzymes in basic cellular function. A special case of gene duplication and
the possible evolution of new functions in the parasitic wasp
Nasonia vitripennis
will also be discussed.
448A
Comparative genetic architectures of similar and independently evolved morphological novelties.
Laurent Arnoult, Caroline Minervino, Benjamin
Prud'homme, Nicolas Gompel. IBDML, UMR CNRS 6216, Case 907, Parc Scientifique de Luminy, 13288 Marseille Cedex 9, France.
A striking and recurrent pattern in evolution is the repeated generation of near identical traits in independent lineages, such as flight in birds and insects or
echolocation in bats and dolphins. Strong evolutionary forces may explain why, in face of similar environmental challenges, similar phenotypic solutions are
being selected again and again. Here we ask: when evolution repeats itself, is it through similar genetic paths? Do developmental mechanisms constrain
these genetic paths by defining a limited set of mutations that can make a new trait? We set to study five independent gains of a pigmentation spot located on
the wings of different Drosophila species: we aim at drawing a fine comparison of the genetic mechanisms underlying these independent gains. Focusing on
one of this species, D. biarmipes, we identified the homeobox transcription factor Distal-less as the major switch controlling the development of the wing
pigmentation spot in this species, through transcriptional regulation of multiple pigmentation genes. We are now using RNA-seq to list new candidates
involved in the making of the spot, and a small hairpin RNA interference technique to test their function in vivo. Confronting these results were are
reconstructing the genetic architecture of the wing pigmentation spot of D. biarmipes; we are now testing whether the same genetic actors are playing the