Molecular Evidence for Natural Hybridization between Cotoneaster dielsianus and C. glaucophyllus.
Molecular Evidence for Natural Hybridization between Cotoneaster dielsianus and C. glaucophyllus.
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栒子与蓝叶栒子自然杂交的分子证据
DOI：
10.3389/fpls.2017.00704
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发表时间：
2017
影响因子：
5.6
通讯作者：
Liao W
中科院分区：
文献类型：
--
作者：
Li M;Chen S;Zhou R;Fan Q;Li F;Liao W
伴随着多倍化和无融合生殖的杂交已经被证明是许多植物进化和物种形成的驱动力。研究与多倍体和无融合生殖相关的杂交进化过程的一个很好的例子是蔷薇科Cotoneaster属，该属约有150种，其中大部分是多倍体无融合生殖。在本研究中，我们调查了分布在云南麻栗坡的所有椰子分类群，中国。根据形态特征，鉴定和取样了4个Cotoneaster分类群：C.dielsianus、C.glucophyllus、C.frchetii和一个可能的杂交种。流式细胞仪分析表明，灰叶锦鸡儿为二倍体，其余3个分类群为四倍体。总共对5个低拷贝核基因和6个叶绿体区域进行了测序，以验证推测的杂交状态。序列分析表明，Dielsianus和Callucophyllus具有较远的亲缘关系，在所研究的11个基因上总共有50个固定核苷酸替换和4个固定inDel，可以很好地将它们分开。所有可能的杂交种的个体都含有相同的序列：它们在5个核基因上与灰叶锦鸡儿在5个核基因上的所有固定差异都显示出层析相加性，在6个叶绿体区域上与灰叶锦鸡儿完全相同。单倍型分析表明，这11个基因有9个单倍型，而蓝藻有10个单倍型，两种之间没有共享的单倍型。推测的杂交种每个核基因都有两个单倍型：一个与Dielsianus共享，另一个与C.glucophyllus共享。它们具有与蓝藻相同的叶绿体单倍型。我们的研究为南方红曲霉和蓝曲霉的自然杂交提供了令人信服的证据，并揭示了所有杂交个体都是通过无融合生殖从一个初始F1衍生而来的。在最初的杂交活动中，青叶锦鸡儿作为母本。我们认为，人类学上的干扰为南方红豆杉和蓝花红豆杉的杂交提供了机会，一个四倍体F1通过无融合生殖成功地培育出了许多相同的后代。在这种情况下，这些Cotoneaster物种的物种完整性可以保持，但对这个新生的杂交种应该保持关注。
Hybridization accompanied by polyploidization and apomixis has been demonstrated as a driving force in the evolution and speciation of many plants. A good example to study the evolutionary process of hybridization associated with polyploidy and apomixis is the genus Cotoneaster (Rosaceae), which includes approximately 150 species, most of which are polyploid apomicts. In this study, we investigated all Cotoneaster taxa distributed in a small region of Malipo, Yunnan, China. Based on the morphological characteristics, four Cotoneaster taxa were identified and sampled: C. dielsianus, C. glaucophyllus, C. franchetii, and a putative hybrid. Flow cytometry analyses showed that C. glaucophyllus was diploid, while the other three taxa were tetraploid. A total of five low-copy nuclear genes and six chloroplast regions were sequenced to validate the status of the putative hybrid. Sequence analyses showed that C. dielsianus and C. glaucophyllus are distantly related and they could be well separated using totally 50 fixed nucleotide substitutions and four fixed indels at the 11 investigated genes. All individuals of the putative hybrid harbored identical sequences: they showed chromatogram additivity for all fixed differences between C. dielsianus and C. glaucophyllus at the five nuclear genes, and were identical with C. glaucophyllus at the six chloroplast regions. Haplotype analysis revealed that C. dielsianus possessed nine haplotypes for the 11 genes, while C. glaucophyllus had ten, and there were no shared haplotypes between the two species. The putative hybrid harbored two haplotypes for each nuclear gene: one shared with C. dielsianus and the other with C. glaucophyllus. They possessed the same chloroplast haplotype with C. glaucophyllus. Our study provided convincing evidence for natural hybridization between C. dielsianus and C. glaucophyllus, and revealed that all hybrid individuals were derivatives of one initial F1 via apomixes. C. glaucophyllus served as the maternal parent at the initial hybridization event. We proposed that anthropological disturbance provided an opportunity for hybridization between C. dielsianus and C. glaucophyllus, and a tetraploid F1 successfully bred many identical progenies via apomixis. Under this situation, species integrity could be maintained for these Cotoneaster species, but attentions should be kept for this new-born hybrid.