生物谷报道：Apicomplexans是动物寄生虫，属于原生动物，包括引起疟疾、弓形虫病和其他人类疾病的病原体。大多数apicomplexans都含有一个未染色的叶绿体残体——apicoplast，它是这种寄生虫生存所必需的。现在，从悉尼港的一个石珊瑚分离出的一种生物有可能填补这一空白。这种藻类与珊瑚一起生活，但也可以作为一种自由生活的生物来培养。从系统发育学上来讲，它与apicomplexan是相关的，因其与甲藻不同，其叶绿体在遗传上有一个新奇之处——它们有光合作用基因，同时结合UGA密码子的使用来编码tryptophan，后者是apicoplasts的典型特征。
生物谷推荐英文原文：
Nature 451, 959-963 (21 February 2008) | doi:10.1038/nature06635; Received 15 September 2007; Accepted 9 January 2008
A photosynthetic alveolate closely related to apicomplexan parasites
Robert B. Moore1,2,11, Miroslav Oborník3,11, Jan Janoukovec3, Tomá Chrudimský3, Marie Vancová3, David H. Green4, Simon W. Wright5, Noel W. Davies6, Christopher J. S. Bolch7, Kirsten Heimann8, Jan lapeta9, Ove Hoegh-Guldberg10, John M. Logsdon2 & Dee A. Carter1
School of Molecular and Microbial Biosciences, University of Sydney, Darlington, New South Wales 2006, Australia
Roy J. Carver Center for Comparative Genomics, Department of Biological Sciences, University of Iowa, Iowa City, Iowa 52242-1324, USA
Biology Centre of the Academy of Sciences of the Czech Republic, Institute of Parasitology, and University of South Bohemia, Faculty of Science, Braniovská 31, 37005 eské Budjovice, Czech Republic
Scottish Association for Marine Science, Dunstaffnage Marine Laboratory, Oban, Argyll PA37 1QA, UK
Australian Antarctic Division, Kingston, Tasmania 7050, Australia
Central Science Laboratory, University of Tasmania, Hobart, Tasmania 7001, Australia
School of Aquaculture, University of Tasmania, Launceston, Tasmania 7250, Australia
School of Marine and Tropical Biology, James Cook University, Townsville, Queensland 4811, Australia
Faculty of Veterinary Science, University of Sydney, Camperdown, New South Wales 2006, Australia
Centre for Marine Studies, University of Queensland, St Lucia, Queensland 4072, Australia
These authors contributed equally to this work.
Correspondence to: Dee A. Carter1 Correspondence and requests for materials should be addressed to D.A.C. (Email: d.carter@mmb.usyd.edu.au).
Abstract
Many parasitic Apicomplexa, such as Plasmodium falciparum, contain an unpigmented chloroplast remnant termed the apicoplast, which is a target for malaria treatment. However, no close relative of apicomplexans with a functional photosynthetic plastid has yet been described. Here we describe a newly cultured organism that has ultrastructural features typical for alveolates, is phylogenetically related to apicomplexans, and contains a photosynthetic plastid. The plastid is surrounded by four membranes, is pigmented by chlorophyll a, and uses the codon UGA to encode tryptophan in the psbA gene. This genetic feature has been found only in coccidian apicoplasts and various mitochondria. The UGA-Trp codon and phylogenies of plastid and nuclear ribosomal RNA genes indicate that the organism is the closest known photosynthetic relative to apicomplexan parasites and that its plastid shares an origin with the apicoplasts. The discovery of this organism provides a powerful model with which to study the evolution of parasitism in Apicomplexa.
