A horizontal gene transfer supported the evolution of an early metazoan biomineralization strategy
1 Courant Research Centre Geobiology, Georg-August-University of Göttingen, Goldschmidtstr. 3, 37077 Göttingen, Germany
2 Department of Earth- and Environmental Sciences & GeoBioCenterLMU, Ludwig-Maximilians-Universität München, Richard-Wagner-Str. 10, 80333 München, Germany
3 Bavarian State Collections of Palaeontology & Geology, Richard-Wagner-Str. 10, 80333 München, Germany
BMC Evolutionary Biology 2011, 11:238 doi:10.1186/1471-2148-11-238Published: 12 August 2011
The synchronous and widespread adoption of the ability to biomineralize was a defining event for metazoan evolution during the late Precambrian/early Cambrian 545 million years ago. However our understanding on the molecular level of how animals first evolved this capacity is poor. Because sponges are the earliest branching phylum of biomineralizing metazoans, we have been studying how biocalcification occurs in the coralline demosponge Astrosclera willeyana.
We have isolated and characterized a novel protein directly from the calcified spherulites of A. willeyana. Using three independent lines of evidence (genomic architecture of the gene in A. willeyana, spatial expression of the gene product in A. willeyana and genomic architecture of the gene in the related demosponge Amphimedon queenslandica), we show that the gene that encodes this protein was horizontally acquired from a bacterium, and is now highly and exclusively expressed in spherulite forming cells.
Our findings highlight the ancient and close association that exists between sponges and bacteria, and provide support for the notion that horizontal gene transfer may have been an important mechanism that supported the evolution of this early metazoan biomineralisation strategy.