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Maternal expression increases the rate of bicoid evolution by relaxing selective constraint
Jeffery P Demuth1, Michael J Wade
1Department of Biology, Indiana University, Bloomington, IN 47405, USA. jpdemuth@indiana.edu
Genetica
|September 7, 2006
Summary
Maternal effect genes, like bicoid (bcd), evolve faster than zygotic genes, such as zerknüllt (zen). This accelerated evolution is due to relaxed selective constraint, confirming population genetic theory.
Area of Science:
- Evolutionary genetics
- Developmental biology
Background:
- Population genetic theory posits differential evolution of maternal effect genes versus genes expressed in both sexes.
- Selection is less effective on autosomal genes expressed in only one sex, potentially leading to faster evolution.
Purpose of the Study:
- To test if maternal effect genes evolve more rapidly than zygotic genes under similar purifying selection.
- To provide molecular evidence for the prediction that reduced selective constraint accelerates maternal gene evolution.
Main Methods:
- Comparative sequence analysis of the tandem gene duplicates, bicoid (bcd) and zerknüllt (zen).
- Assessment of evolutionary rates under similar coefficients of purifying selection.
Main Results:
- The maternal effect gene, bicoid (bcd), evolves significantly faster than the zygotically expressed gene, zerknüllt (zen).
- This finding provides direct molecular evidence confirming theoretical predictions.
Conclusions:
- Relaxed selective constraint is an evolutionary mechanism driving accelerated evolution in maternal effect genes.
- Maternal effect genes possess evolutionary flexibility, enabling them to escape typical constraints on early developmental genes.
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