Clock-based segmentation in the red flour beetle Tribolium castaneum

Doctor of Philosophy === Genetics Interdepartmental Program === Susan J. Brown === In Drosophila, all segments form in the blastoderm where morphogen gradients spanning the entire anterior-posterior axis of the embryo provide positional information. However, in the beetle Tribolium castaneum and mos...

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Main Author: El-Sherif, Ezzat
Language:en_US
Published: Kansas State University 2016
Subjects:
Online Access:http://hdl.handle.net/2097/27648
id ndltd-KSU-oai-krex.k-state.edu-2097-27648
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spelling ndltd-KSU-oai-krex.k-state.edu-2097-276482018-07-22T03:45:32Z Clock-based segmentation in the red flour beetle Tribolium castaneum El-Sherif, Ezzat Tribolium Segmentation Clock Development Evolution Developmental Biology (0758) Doctor of Philosophy Genetics Interdepartmental Program Susan J. Brown In Drosophila, all segments form in the blastoderm where morphogen gradients spanning the entire anterior-posterior axis of the embryo provide positional information. However, in the beetle Tribolium castaneum and most other insects, a number of anterior segments form in the blastoderm, and the remaining segments form sequentially from a posterior growth zone during germband elongation. In this work, I show that segmentation at both blastoderm and germband stages of Tribolium is based on a segmentation clock. Specifically, I show that the Tribolium primary pair-rule gene, Tc-even-skipped (Tc-eve), is expressed in waves propagating from the posterior pole and progressively slowing until they freeze into stripes; such dynamics are a hallmark of clock-based segmentation. Phase shifts between Tc-eve transcripts and protein confirm that these waves are due to expression dynamics. Such waves, like their counterparts in vertebrates, are assumed to arise due to the modulation of a molecular clock by a posterior-to-anterior frequency gradient. I provide evidence that the posterior gradient of Tc-caudal (Tc-cad) expression regulates the oscillation frequency of pair-rule gene expression in Tribolium. I show this by correlating the gradient of Tc-cad expression to the spatiotemporal dynamics of Tc-even-skipped expression in WT as well as in different knockdowns of Tc-cad regulators. Specifically, the spatial extent, frequency, and width of Tc-eve waves correlate with the spatial extent, expression level, and slope of Tc-cad gradient, respectively, as predicted by computer modeling. These results pose intriguing evolutionary questions, since Drosophila and Tribolium segment their blastoderms using the same genes but different mechanisms, and highlight the role of frequency gradients in pattern formation. 2016-02-01T16:57:26Z 2016-02-01T16:57:26Z 2013-12-01 2013 December Dissertation http://hdl.handle.net/2097/27648 en_US Kansas State University
collection NDLTD
language en_US
sources NDLTD
topic Tribolium
Segmentation
Clock
Development
Evolution
Developmental Biology (0758)
spellingShingle Tribolium
Segmentation
Clock
Development
Evolution
Developmental Biology (0758)
El-Sherif, Ezzat
Clock-based segmentation in the red flour beetle Tribolium castaneum
description Doctor of Philosophy === Genetics Interdepartmental Program === Susan J. Brown === In Drosophila, all segments form in the blastoderm where morphogen gradients spanning the entire anterior-posterior axis of the embryo provide positional information. However, in the beetle Tribolium castaneum and most other insects, a number of anterior segments form in the blastoderm, and the remaining segments form sequentially from a posterior growth zone during germband elongation. In this work, I show that segmentation at both blastoderm and germband stages of Tribolium is based on a segmentation clock. Specifically, I show that the Tribolium primary pair-rule gene, Tc-even-skipped (Tc-eve), is expressed in waves propagating from the posterior pole and progressively slowing until they freeze into stripes; such dynamics are a hallmark of clock-based segmentation. Phase shifts between Tc-eve transcripts and protein confirm that these waves are due to expression dynamics. Such waves, like their counterparts in vertebrates, are assumed to arise due to the modulation of a molecular clock by a posterior-to-anterior frequency gradient. I provide evidence that the posterior gradient of Tc-caudal (Tc-cad) expression regulates the oscillation frequency of pair-rule gene expression in Tribolium. I show this by correlating the gradient of Tc-cad expression to the spatiotemporal dynamics of Tc-even-skipped expression in WT as well as in different knockdowns of Tc-cad regulators. Specifically, the spatial extent, frequency, and width of Tc-eve waves correlate with the spatial extent, expression level, and slope of Tc-cad gradient, respectively, as predicted by computer modeling. These results pose intriguing evolutionary questions, since Drosophila and Tribolium segment their blastoderms using the same genes but different mechanisms, and highlight the role of frequency gradients in pattern formation.
author El-Sherif, Ezzat
author_facet El-Sherif, Ezzat
author_sort El-Sherif, Ezzat
title Clock-based segmentation in the red flour beetle Tribolium castaneum
title_short Clock-based segmentation in the red flour beetle Tribolium castaneum
title_full Clock-based segmentation in the red flour beetle Tribolium castaneum
title_fullStr Clock-based segmentation in the red flour beetle Tribolium castaneum
title_full_unstemmed Clock-based segmentation in the red flour beetle Tribolium castaneum
title_sort clock-based segmentation in the red flour beetle tribolium castaneum
publisher Kansas State University
publishDate 2016
url http://hdl.handle.net/2097/27648
work_keys_str_mv AT elsherifezzat clockbasedsegmentationintheredflourbeetletriboliumcastaneum
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