Transposable elements and genome size variations in plants.
Transposable elements and genome size variations in plants.
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DOI：
10.5808/gi.2014.12.3.87
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发表时间：
2014-09
影响因子：
--
通讯作者：
Kim NS
中科院分区：
文献类型：
--
作者：
Lee SI;Kim NS
虽然蛋白质编码基因的数量在植物类群之间变化不大，但它们基因组中的DNA含量变化很大，从0.0648 pg到132.5 pg的1C含量变化高达2，056倍。植物中的平均1C值为2.4 pg，基因组大小的扩展/收缩在植物分类学中具有谱系特异性。植物基因组中的转座因子分数也是可变的，在小基因组中低至~3%，在大基因组中高达~85%，表明基因组大小是转座因子含量的线性函数。在2类转座因子中，第1类长末端重复序列（LTR）反转录转座子的动力学是植物间1C值差异的主要原因。LTR反转录转座子的活性受表观遗传抑制机制的控制。此外，已采用基因组清除机制来平衡基因组大小扩增。随着植物基因组全基因组序列信息的丰富，人们发现，几个基因组清除机制已被采用，这取决于植物类群。百合属和贝母属是被子植物中基因组较大的两个属。在百合科现有属的分化过程中，百合科发生了两次一致的基因组大小进化。除了LTR反转录转座子外，非LTR反转录转座子和卫星DNA可能通过基因组平衡机制的失败而贡献于两个属中的巨大基因组。
Although the number of protein-coding genes is not highly variable between plant taxa, the DNA content in their genomes is highly variable, by as much as 2,056-fold from a 1C amount of 0.0648 pg to 132.5 pg. The mean 1C-value in plants is 2.4 pg, and genome size expansion/contraction is lineage-specific in plant taxonomy. Transposable element fractions in plant genomes are also variable, as low as ~3% in small genomes and as high as ~85% in large genomes, indicating that genome size is a linear function of transposable element content. Of the 2 classes of transposable elements, the dynamics of class 1 long terminal repeat (LTR) retrotransposons is a major contributor to the 1C value differences among plants. The activity of LTR retrotransposons is under the control of epigenetic suppressing mechanisms. Also, genome-purging mechanisms have been adopted to counter-balance the genome size amplification. With a wealth of information on whole-genome sequences in plant genomes, it was revealed that several genome-purging mechanisms have been employed, depending on plant taxa. Two genera, Lilium and Fritillaria, are known to have large genomes in angiosperms. There were twice times of concerted genome size evolutions in the family Liliaceae during the divergence of the current genera in Liliaceae. In addition to the LTR retrotransposons, non-LTR retrotransposons and satellite DNAs contributed to the huge genomes in the two genera by possible failure of genome counter-balancing mechanisms.