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Expression of engrailed during segmentation in grasshopper and crayfish
N H Patel1, T B Kornberg, C S Goodman
1Howard Hughes Medical Institute, Department of Biochemistry, University of California, Berkeley 94720.
Development (Cambridge, England)
|October 1, 1989
Summary
Segmentation in arthropods like grasshoppers, crayfish, and Drosophila shows differences in engrailed protein expression. Despite similar patterns, the generation of these segmentation patterns varies, impacting gene role understanding.
Area of Science:
- Developmental Biology
- Comparative Embryology
- Genetics
Background:
- Arthropod segmentation, the process of forming body segments (metameres), varies across species.
- Drosophila melanogaster exhibits rapid, cell-division-independent segmentation, while other arthropods show gradual, sequential segmentation coupled with cell proliferation.
- Engrailed proteins are key developmental proteins involved in segmentation.
Purpose of the Study:
- To compare the process of segmentation in grasshopper, crayfish, and Drosophila using engrailed protein expression.
- To investigate the similarities and differences in how engrailed patterns are generated during embryogenesis in these diverse arthropods.
- To assess the implications of these differences for the conserved roles of segmentation genes.
Main Methods:
- Utilized a monoclonal antibody specific to engrailed proteins for comparative analysis.
- Examined engrailed expression patterns during the segmented germ band stage in grasshopper, crayfish, and Drosophila embryos.
- Correlated engrailed expression with modes of metameric segmentation (rapid vs. gradual).
Main Results:
- In all three species, engrailed expression patterns at the segmented germ band stage were similar, with parasegments forming first.
- The mechanisms generating these engrailed patterns differed, reflecting distinct modes of metameric development.
- Drosophila shows rapid segmentation without cell division, contrasting with gradual, proliferation-driven segmentation in grasshoppers and crayfish.
Conclusions:
- The conserved engrailed expression pattern suggests a fundamental role in arthropod segmentation.
- Differences in engrailed pattern generation highlight divergent evolutionary strategies for forming metameres.
- The study questions the universal role of Drosophila pair-rule gene homologues in the sequential segmentation of other arthropods.