絲盤蟲（Trichoplax）經(jīng)常是被認為是現(xiàn)存“最簡單”的自由生活的動物,，在關(guān)于早期動物起源的爭論中處在中心位置。它是一種盤狀的“扁盤動物”,，直徑約1毫米,，首次是在一個水族館的墻壁上被發(fā)現(xiàn)的。
現(xiàn)在,，絲盤蟲的基因組已經(jīng)完成測序和分析,。這種動物保留了與刺胞動物和兩側(cè)對稱動物最后共同祖先的很多特征，它們存在于距今超過6億年前,。但絲盤蟲也還有決定發(fā)育模式和細胞類型的基因,，這些細胞類型從未在該動物身上看到過，說明在其生命周期中也許還有尚未被發(fā)現(xiàn)的階段,。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature 454, 955-960 (21 August 2008) | doi:10.1038/nature07191
The Trichoplax genome and the nature of placozoans
Mansi Srivastava1, Emina Begovic1,2, Jarrod Chapman2, Nicholas H. Putnam2,9, Uffe Hellsten2, Takeshi Kawashima1,3, Alan Kuo2, Therese Mitros1, Asaf Salamov2, Meredith L. Carpenter1, Ana Y. Signorovitch4,5, Maria A. Moreno4, Kai Kamm7, Jane Grimwood8, Jeremy Schmutz8, Harris Shapiro2, Igor V. Grigoriev2, Leo W. Buss5,6, Bernd Schierwater4,7, Stephen L. Dellaporta4 & Daniel S. Rokhsar1,2
Center for Integrative Genomics and Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA
Department of Energy Joint Genome Institute, Walnut Creek, California 94598, USA
Okinawa Institute of Science and Technology, Uruma, Okinawa 904-2234, Japan
Department of Molecular, Cellular, and Developmental Biology,
Department of Ecology and Evolutionary Biology, and,
Department of Geology and Geophysics, Yale University, New Haven, Connecticut 06520, USA
Division of Ecology and Evolution, Institut für Tier?kologie und Zellbiologie, Stiftung Tieraerztliche Hochschule Hannover, Bünteweg 17d, D-30559 Hannover, Germany
Stanford Human Genome Center, Stanford University, Stanford, California 94304, USA
Present address: Department of Ecology and Evolutionary Biology, Rice University, Houston, Texas 77005, USA.
As arguably the simplest free-living animals, placozoans may represent a primitive metazoan form, yet their biology is poorly understood. Here we report the sequencing and analysis of the 98 million base pair nuclear genome of the placozoan Trichoplax adhaerens. Whole-genome phylogenetic analysis suggests that placozoans belong to a 'eumetazoan' clade that includes cnidarians and bilaterians, with sponges as the earliest diverging animals. The compact genome shows conserved gene content, gene structure and synteny in relation to the human and other complex eumetazoan genomes. Despite the apparent cellular and organismal simplicity of Trichoplax, its genome encodes a rich array of transcription factor and signalling pathway genes that are typically associated with diverse cell types and developmental processes in eumetazoans, motivating further searches for cryptic cellular complexity and/or as yet unobserved life history stages.
