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Poster Full Abstracts - Evolution and Quantitative Genetics
Poster board number is above title. The first author is the presenter
258
469A
Ecdysone Signaling in Starvation Resistant
Drosophila
.
Lauren A. Reynolds, Allen G. Gibbs. University of Nevada Las Vegas, Las Vegas, NV.
We selected for adult starvation resistance in replicated outbred populations of
Drosophila melanogaster
. These populations accumulate greater lipid stores
as larvae that they can then use to survive adult starvation. Lipids are accumulated during the 3rd instar larval feeding period, which is ~24 hr longer in
starvation-selected populations than controls; the rate of lipid accumulation during larval feeding is the same between starvation-selected populations and
controls. To understand how the developmental delay is achieved we studied gene expression during the 3rd instar. Genes associated with the ecdysone pulse
that results in puparium formation had delayed expression. We partially rescued delayed larval development by feeding 20-hydroxyecdysone (20E) to 3rd
instar larvae, further suggesting a change in the timing of the ecdysone titer. We conclude that selection for adult starvation resistance has resulted in
physiological changes in larvae that are mediated by ecdysone signaling.
470B
Keeping males and females the right size: A closer look at the mechanisms behind sexual size dimorphism.
Nicholas D Testa, Shampa Ghosh-Modak,
Alexander W Shingleton. Zoology, Michigan State University, East Lansing, MI.
Sexual size dimorphism (SSD) is an extraordinarily widespread and conspicuous phenomena in the animal kingdom, yet very little is known of the
underlying developmental mechanisms that generate it. Such a proximate understanding of SSD is essential if we are to completely understand the ultimate
causes of its evolution. Here, we investigate the underlying mechanisms of SSD in the fruit fly Drosophila melanogaster. One important mechanism for the
regulation of SSD in Manduca sexta has been sex-specific differences in critical size, the point in development when starvation no longer delays
development. Here we explore whether critical size also regulates SSD in Drosophila. Previously critical size has been difficult to determine in different
sexes because of the low-survivorship of starved larvae and our inability to determine the sex of pupae that do not eclose. We circumvented this issue by
identifiying the Y-chromosome in pupae using PCR. We show that critical size in Drosophila, as in M. sexta is significantly different between sexes. This
suggests that change in critical size is an important, conserved mechanism in the evolution of SSD in holometabolous insects.
471C
Diverged developmental mechanisms underlying the conserved morphological structures in insect wings.
Yoshinori Tomoyasu, Tingjia Lao, Matthew
Korth. Dept Zoology, Miami Univ, Oxford, OH.
Two structures can be homologous when they have a common origin. Duplication and modification of homologous structures has been a driving force of
animal evolution. Morphological similarity is an important characteristics used to identify homology (
morphological
or
classical homology
). However,
morphological similarity can be deceiving because evolutionary modification can obscure the similarity of homologous structures. An alternative approach is
to identify similarities in the developmental systems, which can be independent of morphological similarity (
developmental
or
deep homology
). Utilizing
these two concepts is a powerful approach to understand the evolution of homologous structures, however, these two concepts often bring different, even
controversial results. Insect wings are fascinating structures to study in regard to homology. All insect wings are considered to be monophyletic (
i.e.
homologous), and it is even possible to homologize each vein among different species. In fact, the vein pattern has been an essential trait for insect
classification. However, the development basis of insect veins has never been explored in the evolutionary context. Studies in
Drosophila
have identified a
battery of genes important for vein formation, some of which are important only for a particular vein (such as
sal, omb, Iro-C, kni, kn, cv
and
ab
). We
depleted the function of these genes via RNAi in the red flour beetle
Tribolium
, and compared the phenotypes to those in
Drosophila
. RNAi for most of the
genes in
Tribolium
resulted in vein abnormality, suggesting that the vein function of these genes has been descended from a common ancestor. Interestingly,
however, the veins affected by the disruption of these genes varied between the two species. This is quite puzzling as these results suggest that a
morphologically homologous structure could be produced by different developmental mechanisms, thus adding another complication to the relationship
between two homology concepts. We will discuss a possible explanation for this apparent disagreement of the two concepts in insect wing veins.
472A
Dramatic Expansion and Expression Diversification of the Methuselah Gene Family During Recent
Drosophila
Evolution.
Mark F. VanBerkum,
Meghna Patel, Dana Hallal, Jeffery Jones, Denise Bronner, Rami Zein, Jason Caravas, Zahabiya Husain, Markus Friedrich. Dept Biological Sciences,
Wayne State University, Detroit, MI.
In
Drosophila melanogastor
, the fifteen Methuselah/Methuselah-like (Mth/Mthl) genes are an insect specific family of GPCRs whose function is largely
unknown. Using
in situ
hybridization techniques, we systematically evaluated the expression of each family member in the embryo and third instar CNS and
imaginal discs. These receptors are expressed in diverse patterns from gastrulation to pupation, and while mesoderm expression (gastrulation and gut)
predominates, expression in neuronal tissue (larval CNS) and the ectoderm (discs) is observed. Six genes (Mthl 1, 5, 9, 11, 13 and 14) are expressed only in
the embryo, four (Mthl3, 4, 6 and 8) in larval tissue, and two (Mthl10 and Mth) in both embryos and larvae. To better understand the evolution of this
expression pattern, we undertook a phylogenetic analysis of this family using receptor sequences from five
Drosophila
species as well as
Tribolium
and
Anopheles
. Mthl1, 5, and 14 are present in each species and form separate clades; a new Mthl gene (CG31720) also forms its own clade. All of the remaining
Drosophila
Mth/Mthl genes, along with a single gene in
Tribolium
, form a large clade of closely related sequences that are further defined by a conserved
Mth ectodomain. The single
Tribolium
Mthl ortholog (Tc010567) provided a unique opportunity to compare the ancestral expression of this Mthl ortholog
with the expression of
Drosophila
paralogs. The
Tribolium
Mthl gene is expressed in the hindgut and a bilateral cluster of mesoderm cells at the border
between the procephalic and gnathal head region. The selective embryonic expression of Tc010567 is strikingly different from the wide spread expression of
the Mthl superclade orthologs in
D. melanogastor
. Thus, our data suggest the acquisition of novel functionalities by gene family expansion during the
evolution of the
Drosophila
lineage. Ongoing work is assessing the functional relevance of the expression patterns in
Drosophila
.
473B
Evolution of morphology and behavior in
Drosophila melanogaster
in response to predation.
Michael DeNieu, Ian Dworkin. Zoology & Ecology,
Evolution and Behavior, Michigan State University, East Lansing, MI.