Minisatellite telomeres occur in the family Alliaceae but are lost in Allium.
Minisatellite telomeres occur in the family Alliaceae but are lost in Allium.
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DOI：
10.3732/ajb.93.6.814
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发表时间：
2006-06
影响因子：
3
通讯作者：
E. Sýkorová;J. Fajkus;M. Mezníková;K. Y. Lim;K. Neplechová;F. Blattner;M. Chase;A. Leitch
中科院分区：
文献类型：
--
作者：
E. Sýkorová;J. Fajkus;M. Mezníková;K. Y. Lim;K. Neplechová;F. Blattner;M. Chase;A. Leitch
虽然端粒序列被认为是高度保守的，但在植物端粒进化中存在着与物种遗传一致的开关点。当天门冬目分化时，拟南芥型端粒小卫星重复序列（TTTAGGG）（n）首先被人类型（TTAGGG）（n）重复序列取代，两者在洋葱（葱科）中丢失。我们的目的是发现（1）当这种损失发生在葱科的分歧，（2）如果（TTAGGG）（n）重复被替换为其他已知的端粒小卫星。采用狭缝印迹杂交、荧光原位杂交、BAL31消化、不对称PCR和克隆等方法对假蕨属、Miersia、Ipheion、Tulbaghia、Gethyum、Gillionum、Leucocoryne、Tristagma和三个主要葱属分支的代表物种中的候选端粒序列进行了鉴定和定位。除葱属之外的葱科属具有形成端粒的人类（TTAGGG）型端粒重复序列。在葱属植物中，只有四膜虫型（TTGGGG）重复序列普遍存在于基因组中，但它们不定位于端粒。同样，拟南芥、人、拟南芥（TTAGG）、衣原体（TTTTAGGG）和尖毛藻（TTTTGGGG）中的共有端粒重复序列在葱端粒中不存在。具有人型端粒的葱科与相关的天冬目物种共享端粒结构。我们证明，在葱属祖先中，人类型端粒重复序列从端粒中丢失，并且没有被任何研究的替代小卫星重复序列取代。然而，人类和其他类型的小卫星端粒重复散布在一些葱基因组和他们的基因组签名与葱分支相吻合。
Although telomere sequences are considered to be highly conserved, there are switch-points in plant telomere evolution that are congruent with species' phylogenies. When Asparagales diverged, the Arabidopsis-type telomeric minisatellite repeat (TTTAGGG)(n) was first replaced by a human-type (TTAGGG)(n) repeat, and both were lost in Allium cepa (Alliaceae). We aimed to discover (1) when this loss occurred during divergence of Alliaceae and, (2) if (TTAGGG)(n) repeats were replaced by other known telomeric minisatellites. Slot-blot hybridization, fluorescent in situ hybridization, BAL31 digestion, asymmetric PCR, and cloning were used to identify and localize candidate telomeric sequences in species of Nothoscordum, Miersia, Ipheion, Tulbaghia, Gethyum, Gilliesia, Leucocoryne, Tristagma, and representatives of the three major Allium clades. Alliaceae genera other than Allium have human (TTAGGG)-type telomeric repeats that form telomeres. In Allium, only Tetrahymena-type (TTGGGG) repeats were ubiquitous in the genome, but they were not localized to telomeres. Likewise, the consensus telomeric repeats in Arabidopsis, human, Bombyx (TTAGG), Chlamydomonas (TTTTAGGG), and Oxytricha (TTTTGGGG) are absent in Allium telomeres. Alliaceae with human-type telomeres share telomere structures with related Asparagales species. We demonstrate that in the Allium ancestor human-type telomeric repeats were lost from telomeres and were not replaced by any investigated alternative minisatellite repeats. However, human and other types of minisatellite telomeric repeats are interspersed in some Allium genomes and their genomic signatures coincide with Allium clades.