Identification and genomic distribution of gypsy like retrotransposons in Citrus and Poncirus
Identification and genomic distribution of gypsy like retrotransposons in Citrus and Poncirus
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DOI：
10.1007/s00122-003-1382-1
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发表时间：
2003-12-01
影响因子：
5.4
通讯作者：
Asíns, MJ
中科院分区：
文献类型：
--
作者：
Bernet, GP;Asíns, MJ
转座元件可能在柑橘遗传不稳定性和基因组进化中发挥重要作用。吉普赛样反转录转座子的存在、它们在柑橘和枳属中的异质性和基因组分布已被研究。从商业品种柑橘中分离出八个含有吉普赛样反转录转座子 POL 编码区部分的克隆，柑橘是柑橘中为数不多的有性物种之一。八个克隆中的四个可能对应于活性元件，因为它们呈现文献中描述的对于活性至关重要的所有保守基序，没有框内终止密码子，也没有移码突变。在这些柑橘元素中的一些和来自马铃薯的抗性基因簇、另一个来自枳实的抗性基因簇以及来自水稻的两种推定的抗性多蛋白之间发现了高度同源性。类似吉普赛元素的嵌套副本散布在柑橘属和枳属基因组中。基因组分布结果表明，这些元件是在两个属分化之前引入的，并在之后分别进化。基于 gypsy 和 copia 类型的逆转录转座子的 IRAP 似乎分布不同，因此基于 gypsy 的 IRAP 证明了柑橘中一组新的、互补的分子标记，可用于研究和绘制遗传变异性，特别是抗病性。与源自科比亚的 IRAP 类似，在枳属中发现的源自吉普赛的 IRAP 的拷贝数和杂合度值低于枳实，而枳实的无融合生殖性较差，是 1970 年之前最常见的柑橘砧木。
Transposable elements might be importantly involved in citrus genetic instability and genome evolution. The presence of gypsy like retrotransposons, their heterogeneity and genomic distribution in Citrus and Poncirus, have been investigated. Eight clones containing part of the POL coding region of gypsy like retrotransposons have been isolated from a commercial variety of Citrus clementina, one of the few sexual species in Citrus. Four of the eight clones might correspond to active elements given that they present all the conserved motifs described in the literature as essential for activity, no in-frame stop codon and no frame-shift mutation. High homology has been found between some of these citrus elements and retroelements within a resistance-gene cluster from potato, another from Poncirus trifoliata and two putative resistance polyproteins from rice. Nested copies of gypsy like elements are scattered along the Citrus and Poncirus genomes. The results on genomic distribution show that these elements were introduced before the divergence of both genera and evolved separately thereafter. IRAPs based on gypsy and copia types of retrotransposons seem to distribute differently, therefore gypsy based IRAPs prove a new, complementary set of molecular markers in Citrus to study and map genetic variability, especially for disease resistance. Similarly to copia-derived IRAPs, the number of copies and heterozygosity values found for gypsy derived IRAPs are lower in Poncirus than in Citrus aurantium, which is less apomictic and the most usual rootstock for clementines until 1970.