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Evolution of repressive and temporal regulatory elements underlies the diversity of Drosophila abdominal pigmentation

Mendez Gonzalex, Ivan David (2023) Evolution of repressive and temporal regulatory elements underlies the diversity of Drosophila abdominal pigmentation. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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A major question in evolutionary biology concerns the developmental origin of morphological diversity. Changes in gene regulation are known to contribute to developmental differences producing morphological variation. Interspecific divergence in gene expression often results from changes in transcription-stimulating enhancer elements. However, the role of other kinds of regulatory elements in this process has been less explored. In my doctoral work, I used the abdominal melanic pigmentation of Drosophila to analyze how changes in the function of distinct regulatory elements
can contribute to morphological evolution. In Chapter 1, I investigated the contribution of repressive transcriptional silencers. I show that the Drosophila pigmentation gene ebony has mainly evolved through changes in the spatial domains of silencers that pattern its abdominal expression. By precisely editing the endogenous ebony locus of D. melanogaster, I demonstrate the requirement of two redundant abdominal enhancers and three silencers that repress the redundant enhancers in patterned manner. Then, I demonstrate that transcriptional silencers have been involved in every case of ebony evolution observed to date. These findings suggest that negative regulation by silencers likely has an under-appreciated role in gene regulatory evolution. In Chapter2, I studied the evolution of temporal regulation of the Hox-gene Abd-B. The expression of this gene during mid pupal development is crucial for the formation of male-specific abdominal melanic pigmentation. I show that this
expression pattern evolved recently in D. melanogaster and closely related species. I identified two temporally restricted cis-regulatory elements required for this expression pattern. Furthermore, using allele replacements, I show that the function of these CREs is highly conserved even in species lacking Abd-B expression. My results
suggest that a novel expression pattern evolved using conserved CREs, and suggests the existence of changes in unknown silencers, and/or upstream factors. I propose
that heterochronic shifts in Hox-gene expression might be a common mechanism to modify the morphology of animal segments while reducing pleiotropic effects. In summary, my work highlights the importance of repression and temporal regulation in the evolution of novel expression patterns and morphological traits.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Mendez Gonzalex, Ivan
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Thesis AdvisorRebeiz,
Committee ChairCampbell,
Committee MemberLee,
Committee MemberBerman,
Committee MemberWilliams,
Date: 26 January 2023
Date Type: Publication
Defense Date: 18 October 2022
Approval Date: 26 January 2023
Submission Date: 24 October 2022
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 133
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Biological Sciences
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: evolution, gene regulation, drosophila
Date Deposited: 26 Jan 2023 13:38
Last Modified: 26 Jan 2023 13:38


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