来自Queensland大学的科学家们正在研究被称为基因世界“罗塞塔石碑”的进化问题，他们研究的是一种低等生物——海绵的发育过程。
由UQ生物学教授Bernie Degnan领导的一个小组发现，海绵体内不存在Hox基因——这是一种在各种动物甚至包括人类中都存在的基因，它负责区分身体头和尾端的发育方向。
Degnan教授表示：“海绵是一种活化石，自从寒武纪生物大爆发以来它就没怎么改变过，寒武纪大爆发是大部分动物首次在地球上出现的时期。海绵是最简单的动物之一，但是其基因组信息却和人类的比较类似。”
他接着说：“我们发现海绵没有这一基因，因此它一定出现在海绵和我们分离进化之后，而且这和向着复杂生物的大幅度进化相关。”
小组的研究结果发表在最新的刊物《Current Biology》上，Degnan教授认为这一成果为揭开地球生物是如何进化的谜团提供了新的线索。他说：“海绵是一种非常迷人的生物，因为它为我们提供了一扇通向过去的窗口。但同时它们又打开了一扇通向未来的窗户——海绵是一种生物活性物质的丰富资源库，这在医药学和工业上都有很大用途。”
其中一种可能的用途就是将海水中的硅分离出来得到玻璃，这将是一种在未来环保的玻璃生物制造法。而同时还有很多科学家在研究用海绵制造新型药物。目前Degnan小组正在进一步研究这种简单但是吸引人的生物。
原文链接：http://www.physorg.com/news96866963.html
??刘乐译自：physorg.com
原始出处:
Current Biology, Vol 17, 706-710, 17 April 2007
Report
The NK Homeobox Gene Cluster Predates the Origin of Hox Genes
Claire Larroux,1 Bryony Fahey,1 Sandie M. Degnan,1 Marcin Adamski,1 Daniel S. Rokhsar,2,3 and Bernard M. Degnan1,
1 School of Integrative Biology, The University of Queensland, Brisbane Qld 4072, Australia
2 DOE Joint Genome Institute, 2800 Mitchell Avenue, Walnut Creek, California 94598
3 Center for Integrative Genomics, Department of Molecular and Cell Biology, University of California, Berkeley, California 94720
Corresponding author
Bernard M. Degnan
b.degnan@uq.edu.au
Hox and other Antennapedia (ANTP)-like homeobox gene subclasses—ParaHox, EHGbox, and NK-like—contribute to key developmental events in bilaterians [1, 2, 3, 4]. Evidence of physical clustering of ANTP genes in multiple animal genomes [4, 5, 6, 7, 8, 9] suggests that all four subclasses arose via sequential cis-duplication events. Here, we show that Hox genes' origin occurred after the divergence of sponge and eumetazoan lineages and occurred concomitantly with a major evolutionary transition in animal body-plan complexity. By using whole genome information from the demosponge Amphimedon queenslandica, we provide the first conclusive evidence that the earliest metazoans possessed multiple NK-like genes but no Hox, ParaHox, or EHGbox genes. Six of the eight NK-like genes present in the Amphimedon genome are clustered within 71 kb in an order akin to bilaterian NK clusters. We infer that the NK cluster in the last common ancestor to sponges, cnidarians, and bilaterians consisted of at least five genes. It appears that the ProtoHox gene originated from within this ancestral cluster after the divergence of sponge and eumetazoan lineages. The maintenance of the NK cluster in sponges and bilaterians for greater than 550 million years is likely to reflect regulatory constraints inherent to the organization of this ancient cluster.
