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Published on: March 15, 2016
Parallel evolution of nacre building gene sets in molluscs
Daniel J Jackson1, Carmel McDougall, Ben Woodcroft
1School of Biological Sciences, University of Queensland, Brisbane, Australia.
Molecular Biology and Evolution
|November 17, 2009
Summary
Shell formation in molluscs like oysters and abalone shows significant genetic differences, suggesting convergent evolution. Novel shell proteins evolved independently multiple times in animals.
Area of Science:
- Evolutionary Biology
- Molecular Biology
- Biomineralization
Background:
- The Cambrian explosion saw the rise of skeletonized animals, with molluscan shell evolution potentially occurring independently.
- Understanding the genetic basis of shell formation is key to deciphering early animal diversification.
Purpose of the Study:
- To investigate the evolutionary origins of shell biomineralization by comparing gene expression in nacre-forming cells of a bivalve and a gastropod.
- To identify conserved and divergent genes involved in shell matrix formation.
Main Methods:
- Comparative transcriptomics of nacre-forming mantle cells from Pinctada maxima (bivalve) and Haliotis asinina (gastropod).
- Analysis of gene clusters, secreted proteins, and proteins with repetitive low-complexity domains (RLCDs).
- Examination of extracellular matrix proteins, including chitin-related genes.
Main Results:
- Less than 10% of gene clusters are shared between the two species after removing housekeeping genes.
- Significant differences were found in secreted proteins and RLCD proteins, with unique domains in each species.
- Fundamental differences in chitin-related genes suggest distinct organic matrix compositions.
Conclusions:
- The genetic underpinnings of nacre formation in bivalves and gastropods are largely divergent, supporting convergent evolution.
- The independent evolution of biomineralizing RLCD proteins in molluscs and echinoderms indicates multiple evolutionary origins.
- Shell biomineralization pathways have evolved repeatedly across the Metazoa.
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