美國科學(xué)家的一項(xiàng)最新研究,，首次在水螅中找到了動物感光性的起源——視蛋白,。相關(guān)論文發(fā)表在最新一期的《公共科學(xué)圖書館.綜合》（PLoS ONE）上,。
領(lǐng)導(dǎo)最新研究的是美國加州大學(xué)圣芭芭拉分校的Todd Oakley,，他和同事是最早在刺胞動物（cnidarians,，包括珊瑚、水母,、?？龋ふ腋泄饣虻目茖W(xué)家。
水螅也是刺胞動物的一種,，主要生活在熱帶和溫帶,，沒有眼睛或其它感光器官。不過,，新的研究表明,，它們體內(nèi)確實(shí)存在著感知光線的遺傳路徑。
研究發(fā)現(xiàn),，水螅的視蛋白遍布全身,，但在嘴部區(qū)域尤其集中。因此研究人員推測,，水?？赡芾酶泄庑詠韺ふ耀C物。
論文第一作者David Plachetzki表示,，“我們在更早的分支物種比如海綿中沒有找到視蛋白,，因此我們能夠?yàn)閯游锔泄膺M(jìn)化過程限定一個最早時間。而最新的研究讓我們有了確切的時限,，最早擁有感光能力的物種大約生活在距今6億年前,。”
最新的研究還確定了水螅中視蛋白基因的進(jìn)化歷史。Oakley表示,，“我們清楚地發(fā)現(xiàn),，視蛋白同源復(fù)制基因所發(fā)生的變化使得新基因與不同蛋白以全新的方式發(fā)生聯(lián)系和作用，而這些已經(jīng)成為今天視覺遺傳機(jī)制的根基,。”
值得一提的是,，澳大利亞昆士蘭大學(xué)的Bernie Degnan為此次研究提供了重要的生物信息學(xué)工具。而由Craig Venter研究所實(shí)施的水螅基因組計劃也正在緊鑼密鼓的進(jìn)行當(dāng)中,。（科學(xué)網(wǎng) 任霄鵬/編譯）
原始出處:
PLoS ONE
Received: July 12, 2007; Accepted: September 17, 2007; Published: October 17, 2007
The Origins of Novel Protein Interactions during Animal Opsin Evolution
David C. Plachetzki1, Bernard M. Degnan2, Todd H. Oakley1*
1 Ecology, Evolution and Marine Biology, University of California at Santa Barbara, Santa Barbara, California, United States of America, 2 School of Integrative Biology, University of Queensland, Brisbane, Queensland, Australia
Abstract
Background
Biologists are gaining an increased understanding of the genetic bases of phenotypic change during evolution. Nevertheless, the origins of phenotypes mediated by novel protein-protein interactions remain largely undocumented.
Methodology/Principle Findings
Here we analyze the evolution of opsin visual pigment proteins from the genomes of early branching animals, including a new class of opsins from Cnidaria. We combine these data with existing knowledge of the molecular basis of opsin function in a rigorous phylogenetic framework. We identify adaptive amino acid substitutions in duplicated opsin genes that correlate with a diversification of physiological pathways mediated by different protein-protein interactions.
Conclusions/Significance
This study documents how gene duplication events early in the history of animals followed by adaptive structural mutations increased organismal complexity by adding novel protein-protein interactions that underlie different physiological pathways. These pathways are central to vision and other photo-reactive phenotypes in most extant animals. Similar evolutionary processes may have been at work in generating other metazoan sensory systems and other physiological processes mediated by signal transduction.
Figure 1. Sequence motifs and expression of cnidarian opsin in the nerve net of Hydra magnipallata.
(A) Sequence alignment of 4th cytoplasmic loop region of animal opsins used in this study indicating the Lys 296 chromophore binding site (arrowhead) and the G protein-binding tripeptide (asterisks). (B) In situ hybridization with Hm2 cnidops probe. Asterisk denotes the hypostome. Opsin is expressed most strongly in a ring of sensory neurons that surround the mouth. Inset, oral view.
全文鏈接：http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0001054
