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Poster Full Abstracts - Evolution and Quantitative Genetics
Poster board number is above title. The first author is the presenter
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diverged. We are comparing the sequence, expression and activity of these genes, making use of tools being developed in Aedes for functional studies. To
compare expression patterns, in situ hybridizations are being performed with Aa-ftz, Aa-Antp, and Aa-ftz-f1 in early mosquito embryos. To assess the
function of these genes in mosquitoes, both loss-of function and gain-of-function approaches are being used. The former is being carried out by RNAi while
the latter is being done by generating transgenic mosquitoes. These transgenic mosquitoes will be used to mis-express Aa-ftz and Aa-Anp to determine
whether this results in pair-rule or homeotic transformation phenotypes, similar to those seen in Drosophila melanogaster. Together, these results will
provide insight into the molecular mechanisms underlying evolution of regulatory genes in an insect lineage.
453C
Genome-wide comparison among
melanogaster
sibling species reveals novel genes involved in myogenesis diversification.
Ryan M Haskins, Yunyi
Yang, Youngmin Chu, Juan S Chahda, Joseph Schinaman, Mirela Belu, Lyndsie Haefke, Rui Sousa-Neves, Claudia M Mizutani. Biology, Case Western
Reserve University, Cleveland, OH.
The
Drosophila
genus comprises a number of species with remarkable adaptations to unique environments.
D. melanogaster
,
D. simulans
and
D. sechellia
are three sibling species of particular interest since they exhibit significant developmental and behavioral differences despite their recent divergence. To
begin probing these differences and gain a better understanding of the mechanisms that operate in species differentiation, we reconstructed the genomes of
D. sechellia
and
D. simulans
and made pair-wise BLAST analysis of coding sequences against the
D. melanogaster
genome (Sousa-Neves, R. and Rosas, A.,
2010). By selecting the group of genes that are most similar between
D. simulans
and
D. sechellia
, but most divergent in
D. melanogaster
(i.e. ancestral
alleles of
D. simulans
and
D. sechellia
), we expected to identify genes that distinguish these two newer species from
D. melanogaster
. In this work, we
screened for candidate ancestral alleles to be involved in a novel phenotypic variation of myoblast fusion that distinguishes
D. melanogaster
from its other
sibling species. We selected genes expressed in a narrow window of embryonic development when myogenesis takes place. Our screening led to the
identification of two novel genes:
snail-minded
(
sami
) and
pick-up sticks
.
sami
is expressed in the presumptive mesoderm and mesodectoderm, in a
combined pattern of both
single-minded
and
snail
, an essential gene for muscle development.
pick-up sticks
encodes a predicted EGF-like secreted protein
that initiates expression during somatic myoblast fusion and remains exclusively expressed in the somatic body muscle fibers. Functional analyses of the two
genes are currently under way. The screening method presented here could theoretically be applied to any biological processes relevant to the diversification
of this group of species, and may provide a valuable tool in addition to classical mutagenesis screenings to identifying novel developmental genes.
454A
A Homeodomain-dependent Function in a Rapidly Evolving
Hox
Gene in Insects.
Alison Heffer, Leslie Pick. Dept Entomology, Univ Maryland,
College Park, MD.
Hox
genes are considered to be evolutionarily constrained because of their importance in determining segment identity in metazoans, and because
mutations or mis-expression result in homeotic transformations.
fushi tarazu (ftz)
is a rapidly evolving
Hox
gene in insects that has switched in both
expression and function from
Hox
-like in basal arthropods to pair-rule segmentation in
Drosophila
. In addition to its early role in segmentation,
Dm-ftz
is
also required later in embryonic development in the central nervous system (CNS), specifically in RP2 neuron formation. We previously isolated Ftz from
several insects spanning 450 million years of evolution, and found great diversity in expression and protein sequence. Despite this,
ftz
expression in the
developing CNS of arthropods has been retained. Here we examine which motif or domain in the Ftz coding region is important for CNS function. To do
this, Ftz transgenes containing mutations in the segmentation LXXLL motif, degenerated homeotic YPWM motif, and DNA-binding homeodomain were
made, and all were placed under the control of the
ftz
neurogenic cis-regulatory element. The LXXLL and FNWS in
Dm
-Ftz were mutated to abolish all
function, and the Ftz homeodomain was deleted, changed to the sequence of the N-terminal arm of
Dm
-Antp, or to the entire
Dm
-Antp homeodomain. Using
a mutant
Drosophila
line that lacks the
ftz
neurogenic expression, we tested the ability of each of Ftz transgenes to rescue the RP2- phenotype, marked by
loss of Eve expression. Here we report that neither the LXXLL or FNWS motifs are required for Ftz CNS function. Rather it is the homeodomain, and not
specifically the Ftz homeodomain, that is required for function in the nervous system. Together, these results suggest that
ftz
has been maintained in the
genomes of all insects examined to date because of its role in CNS development, which is homeodomain-dependent. This constraint later in development did
not prevent Ftz from being co-opted into earlier developmental pathways as long as variations in expression and protein sequence did not impact CNS
function.
455B
How different are mosquitoes and Drosophila?—Evolution of mosquito early zygotic genes.
Wanqi Hu, James Biedler, Zhijian Tu. Biochemistry,
Virginia Tech, Blacksburg, VA.
The beginning of embryogenesis is controlled by maternal transcripts and proteins. The zygotic genome starts to take over during the maternal-to-zygotic
transition. Early zygotic genes are considered to play essential roles in embryogenesis. We have identified more than 100 pure early zygotic genes (without
maternal expression) in the yellow fever mosquito
Aedes aegypti
by RNAseq and subsequent RT-PCR. This gene list has little overlap with the known early
zygotic genes in Drosophila, indicating rapid evolutionary turnover. Interestingly, these novel early zygotic genes tend to have domains or characteristics
consistent with functions related to early embryonic development. Phylogenetic analysis confirmed that many of the pure early zygotic genes are
A. aegypti
or mosquito specific. Gene duplication and subsequent acquisition of early zygotic expression profile may explain the origin of a number of the novel early
zygotic genes.
456C
Functional genomic analysis of eye development in the red flour beetle
Tribolium castaneum
.
Zahabiya Husain
1
, Anura Shrivastava
1
, Arun K Sasikala -
Appukuttan
1
, Bryce Daines
2
, Rui Chen
2
, Markus Friedrich
1
. 1) Wayne State University, Detroit, MI; 2) (2) Human Genome Sequencing Center, Department
of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
The lineages leading to the red flour beetle
Tribolium castaneum
and the fruit fly
Drosophila melanogaster
separated at least 250 million years ago.
Previous work in our lab suggests that this evolutionary separation resulted in major differences regarding the organization of the retinal determination gene
network (RDGN). In
Drosophila
, mutations in the Pax6 transcription factor genes
eyeless (ey)
and
twin of eyeless (toy)
cause loss or reduction of the