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Dissertation Information for David R. Angelini

NAME:
- David R. Angelini

DEGREE:
- Ph.D.

DISCIPLINE:
- Biology

SCHOOL:
- Indiana University (USA) (2005)

ADVISORS:
- Thomas C Kaufman

COMMITTEE MEMBERS:
- Edmund D. Brodie
- Joseph B. Duffy

MPACT Status: Incomplete - Not_Inspected

Title: Comparative developmental genetics of appendages and other structures of the milkweed bug, Oncopeltus fasciatus

Abstract: The arthropods display a wide range of morphological diversity. What roles do genes and development play in the evolution of morphological diversity, and how might they differ between species? To explore these issues, I have conducted a series of comparative investigations of appendage development in the milkweed bug, Oncopeltus fasciatus (Heteroptera). The appendages of Oncopeltus develop from embryonic limb buds, which is the primitive arthropod state. However, the mouthparts of Oncopeltus are independently modified, relative to other insect orders, providing an example of morphological novelty.

I have focused my studies on three levels of appendage development: specification of appendage and body segment identity by the homeotic complex (Hox) genes, establishment of appendage primordia and limb axes, and the specification of proximal-distal (PD) domains.

The Hox genes of Oncopeltus function to specify body segment identity, as in model species, with several noteworthy differences: Oncopeltus Antennapedia is required for the identity of all thoracic segments. The temporally modulated interactions of proboscipedia and Sex combs reduced vary from other insects. While abdominal Hox genes obey posterior prevalence, their interactions are not at the level of transcription, suggesting post-translational competition.

Current models for the specification of limb primordia and the limb PD axis are based on studies of Drosophila melanogaster . In this species, appendages arise in a derived manner from imaginal discs, and require the signaling molecule encoded by wingless ( wg ). In Oncopeltus , RNA interference of Wg signaling produces defects in the germband, but not in the appendages. This suggests that Wg signaling is functionally conserved in the development of the germband but is not essential in the specification of the limb PD axis or primordia in Oncopeltus .

Functional and expression analyses of PD domain genes in Oncopeltus demonstrate them to be well conserved in the legs, but divergent in the development of other appendage types. The derived Oncopeltus mouthparts show novel patterns of gene expression and function, while antenna identity does not require wildtype Distal-less activity in Oncopeltus , as it does in Drosophila .

Data from these and other studies are used to evaluate hypotheses for the evolution of developmental mechanisms in insect appendages.

MPACT Scores for David R. Angelini

A = 0
C = 0
A+C = 0
T = 0
G = 0
W = 0
TD = 0
TA = 0
calculated 2010-09-30 19:31:58

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