Sex or no sex? Group I introns and independent marker genes reveal the existence of three sexual but reproductively isolated biospecies in Trichia varia (Myxomycetes)
Sex or no sex? Group I introns and independent marker genes reveal the existence of three sexual but reproductively isolated biospecies in Trichia varia (Myxomycetes)
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DOI：
10.1007/s13127-015-0230-x
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发表时间：
2015-12-01
影响因子：
1.6
通讯作者：
Schnittler, Martin
中科院分区：
文献类型：
--
作者：
Feng, Yun;Schnittler, Martin
疟原虫黏菌是变形虫类的成员，形成精致的子实体，释放空气中的孢子。两个种的概念已经独立发展：形态依赖于子实体特征，生物学依赖于几个可栽培物种的杂交研究。为了协调这两个概念，我们从198个常见物种的标本中获得了三个独立标记(核小亚基(SSU)核糖体RNA基因，染色体外；延伸因子1α基因，染色体；细胞色素氧化酶亚单位1基因，线粒体)的部分序列。由此产生的系统发育图显示，21个三标记基因类型聚为三个组。单标记基因类型的组合仅出现在这些组中，称为1、2a和2b。为了考察第一组内含子监测物种形成事件的适宜性，对66个样本进行了完整的SSU序列测定，揭示了六个可以携带第一组内含子的位置。在第1和2a组中，有5个位置被不同的内含子基因所占据，两组之间没有相同的基因。2b组无内含子。在组1和组2a的不同位置发现了可能具有功能或退化的归巢核酸内切酶基因。所有的观察结果(三个标记的基因组合、重组迹象、内含子模式)都很符合三个神秘的生物物种的模式，这些物种繁殖的主要是有性繁殖，但繁殖是孤立的。第一组内含子和插入的归巢内切酶基因的模式越来越多地证据表明，Goddard-Burt内含子生命周期模型适用于自然发生的粘菌种群。
Plasmodial slime molds are members of the class Amoebozoa forming elaborate fruit bodies releasing airborne spores. Two species concepts have been developed independently: a morphological relying on fruit body characters, and a biological relying on crossing studies of a few cultivable species. In an attempt to reconcile both concepts, we obtained for 198 specimens of the common species Trichia varia partial sequences of three independent markers (nuclear small-subunit (SSU) ribosomal RNA gene, extrachromosomal; elongation factor 1 alpha gene, chromosomal; cytochrome oxidase subunit 1 gene, mitochondrial). The resulting phylogeny revealed 21 three-marker genotypes clustering into three groups. Combinations of the single-marker genotypes occurred exclusively within these groups, called 1, 2a, and 2b. To examine the suitability of group I introns to monitor speciation events, complete SSU sequences were generated for 66 specimens, which revealed six positions that can carry group I introns. For each of the groups 1 and 2a, five of these positions were occupied by different intron genotypes; and no genotype was shared by the two groups. Group 2b was devoid of introns. Putatively functional or degenerated homing endonuclease genes were found at different positions in groups 1 and 2a. All observations (genotypic combinations of the three markers, signs of recombination, intron patterns) fit well into a pattern of three cryptic biological species that reproduce predominantly sexual but are reproductively isolated. The pattern of group I introns and inserted homing endonuclease genes mounts evidence that the Goddard-Burt intron life cycle model applies to naturally occurring myxomycete populations.