Courant Research Centre Geobiology, Georg-August-University of Göttingen, Goldschmidtstrasse 3, Göttingen, Germany.
BMC Evol Biol. 2011 Aug 12;11:238. doi: 10.1186/1471-2148-11-238.
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.
在 5.45 亿年前的晚前寒武纪/早寒武纪时期，同步广泛地获得生物矿化能力是后生动物进化的一个决定性事件。然而，我们对动物最初如何进化出这种能力的分子水平的理解还很有限。由于海绵是最早分支的生物矿化后生动物门，我们一直在研究珊瑚状淡水海绵（Astrosclera willeyana）中的生物钙化是如何发生的。
我们从 A. willeyana 的钙化球晶中直接分离和鉴定了一种新型蛋白质。利用三条独立的证据线索（A. willeyana 中基因的基因组结构、基因产物在 A. willeyana 中的空间表达以及相关的钙质海绵 Amphimedon queenslandica 中的基因基因组结构），我们表明编码该蛋白的基因是从细菌水平获得的，并且现在高度且仅在球晶形成细胞中表达。
我们的发现强调了海绵和细菌之间存在的古老而密切的联系，并为水平基因转移可能是支持这种早期后生动物生物矿化策略进化的重要机制的观点提供了支持。
