Genome-Wide analysis of Marsupial Retroposons: Phylogenetic markers for reconstructing their Evolution

有袋类和胎盘类哺乳动物大约在1.3亿年前从一个共同的祖先分化而来。有袋类动物大约有280种，与大约4500种胎盘哺乳动物相比，它们的数量很少；然而，有袋类动物的物种间关系仍然不清楚。南美负鼠的第一个完全测序的有袋类基因组显示出令人惊讶的高反转录积累量(52%)，这在迄今测序的所有哺乳动物基因组中是无与伦比的。在澳大利亚袋鼠身上也发现了同样高但非常不同的逆转录酶活性，这表明有袋类基因组特别适合于基于逆转录酶的进化研究。我们打算使用现有的基因组数据结合广泛的物种样本，包括已灭绝的标本，以(1)通过追踪数百个特定谱系的逆转录病毒，明确地重建有袋类动物及其生物地理的进化，(2)建立有袋类逆转录病毒的积累和基因组塑造能力的完整历史图景，以及(3)使用高通量cDNA应用程序研究它们对转录组的当前影响。

Marsupial and placental mammals diverged from a common ancestor approximately 130 million years ago. There are about 280 species of marsupials, which are sparsely represented when compared to the roughly 4500 placental mammals; nevertheless, interspecies relationships of marsupials are still obscure. The first completely sequenced marsupial genome of the South American opossum revealed a surprisingly high accumulation of retroposons (52%), which is unrivalled among all mammalian genomes sequenced to date. A similarly high but very different profile of retroposon activity is seen in the Australian kangaroo, indicating that marsupial genomes are exceptionally suitable for retroposon-based investigations of their evolution. We intend to use available genome data in combination with a broad species sampling, including an extinct specimen, to (1) unambiguously reconstruct the evolution of marsupials and their biogeography by tracing hundreds of lineage-specific retroposons, (2) develop a complete historical picture of the accumulation and genome-shaping power of marsupial retroposons, and (3) investigate their current impact on the transcriptome using high-throughput cDNA applications.