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

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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.