Genetic identity of free-living Symbiodinium obtained over a broad latitudinal range in the Japanese coast
Genetic identity of free-living Symbiodinium obtained over a broad latitudinal range in the Japanese coast
复制标题
DOI：
10.1111/pre.12004
复制
发表时间：
2013-01-01
影响因子：
1.5
通讯作者：
Koike, Kazuhiko
中科院分区：
文献类型：
--
作者：
Yamashita, Hiroshi;Koike, Kazuhiko
甲藻共生藻是众所周知的从事共生与各种海洋动物，包括珊瑚。最近的环境共生藻（发生在环境中，与宿主动物分开;通常被称为自由生活的共生藻）的记录特别令人感兴趣，因为这些环境种群是许多宿主动物的共生体来源。在本研究中，我们进行了系统发育分析的环境共生藻分离株（培养菌株）从沙子，潮池，或大型藻类表面，和环境DNA克隆提取的水柱，在日本各地的许多网站。我们基于核rRNA基因（内转录间隔区-1、-2和5.8S）的系统发育分析表明，大多数环境分离物在Clade-A谱系内形成单系亚支，并从具有高自举值的宿主相关Clade-A群体中分离出来。部分核28 S rDNA同源性分析和膜板观察结果表明，这些环境分离物与一个已知的浮游种共生甲藻（Symbiodinium natans Gert汉森et Daugbjerg）密切相关，该种共生甲藻是从东北大西洋的浮游网样品中分离的。另一方面，环境中的DNA克隆也被注意到，主要是嵌套在主机相关的共生藻群分散在各个分支。这些结果导致的假设，环境共生藻可以分为两组。一组，在本研究和以前的报告中，以环境分离株为代表，可能是完全自由生活的;另一组暂时存在于自由生活的形式，可能已被驱逐出动物宿主。后一组中的种群可能代表了可行共生体的环境来源，因为这些共生体通常与宿主相关。然而，在前组的共生甲藻预计不会从事稳定的共生与宿主刺胞动物。
The dinoflagellate Symbiodinium is well known to engage symbiosis with various marine animals, including corals. Recent records of environmental Symbiodinium (occurring in the environment and separately from host animals; usually referred to as free-living Symbiodinium) are of special interest, since these environmental populations are essential as symbiont sources for many host animals. In the present study, we carried out a phylogenetic analysis of environmental Symbiodinium isolates (culture strains) from sand, tide pools, or macroalgal surfaces, and environmental DNA clones extracted from the water-column, at numerous sites around Japan. Our phylogenetic analysis based on the nuclear rRNA gene (internal transcribed spacers -1, -2, and 5.8S), indicated that most of the environmental isolates form monophyletic subclades within the Clade-A lineage, and separate from a host-associated Clade-A population with high bootstrap values. Results of the partial nuclear 28S rDNA phylogeny and thecal-plate observations revealed that these environmental isolates were closely related to a previously-described planktonic species, Symbiodinium natans Gert Hansen et Daugbjerg, which was isolated from a plankton-net sample from the Northeast-Atlantic Ocean. On the other hand, the environmental DNA clones were also noted to be mostly nested within host-associated Symbiodinium groups scattered in various clades. These results led to the assumption that the environmental Symbiodinium can be divided into two groups. One group, as typified by environmental isolates in the present study and previous reports, may be exclusively free-living; the other group exists transiently in free-living forms, possibly having been expelled from animal hosts. The populations within the latter group probably represent environmental sources of viable symbionts, because these are normally host-associated. However, the Symbiodinium in the former group are not expected to engage in stable symbioses with host cnidarians.