Genome Sequence of an Australian Kangaroo, Macropus eugenii

Janine E Deakin, Australian National University, Canberra, Australia

Published online: March 2013

DOI: 10.1002/9780470015902.a0023980

The tammar wallaby (Macropus eugenii) is a model marsupial species that has been intensively used for research into various aspects of marsupial biology. Recently, it became one of only three marsupial species to have its genome sequenced. Comparisons of genome sequence from all three marsupials with those of other vertebrates have made it possible to begin identifying marsupial-specific genome features. Our knowledge of the biology of the tammar wallaby has informed the interpretation of these unique features and provided insight into their evolution. Among these unique features are genes involved in the sophisticated marsupial lactation system and genes encoding for potent antimicrobial peptides. Comparisons of genome organisation have also provided insight into marsupial genome evolution.

Key Concepts:

  • Uncovering the genetic basis of unique marsupial features is now possible due to the availability of genome sequences for three marsupial species.
  • The tammar wallaby is a model species used for studies into marsupial biology, making it possible to link genomic features with the biological characteristics.
  • As the tammar wallaby genome was only lightly sequenced, other genomic resources such as transcriptome sequences and genome maps have enhanced the genome assembly.
  • A number of novel genes are associated with the complex marsupial lactation system and immunity.
  • Five novel genes have been identified on the marsupial Y chromosome.
  • The organisation of the tammar wallaby major histocompatibility complex is vastly different to that of any other species studied to date.
  • A decades old debate over chromosome number in the ancestral marsupial has been resolved by comparing genome organisation among the sequenced marsupials species and the outgroup species human and chicken.
  • The wallaby genome assembly in combination with other genomic resources are proving valuable for the discovery of marsupial-specific features.

Keywords: marsupial; genome evolution; mammals; comparative genomics; lactation

Figure 1. The phylogenetic relationship and estimated divergence times of the three marsupial species for which genome sequence is available and representative outgroups of the eutherian, monotreme and avian clades.
Figure 2. Lactation stages in the tammar wallaby. The timing of changes in milk composition and mammary gland gene expression are indicated; solid colour corresponds to the highest concentration of the specified component or gene. CATH refers to cathelcidin genes (only 6 of the 14 detected in the wallaby genome were tested for expression in Wang et al., 2011c).
Figure 3. Comparative organisation of the MHC region in representatives of different vertebrate lineages. The organisation of the wallaby MHC is very different to that of the opossum, its closest relative depicted on this phylogeny. Class II genes are found on either side of the Class III region and Class I genes have been localised to nine other regions of the genome, in addition to the core MHC. Modified from Deakin (2012).
Figure 4. FISH mapping of two genes (one labelled in red and the other in green) from the ends of an opossum–human conserved block of genes onto tammar wallaby chromosome 4.
Figure 5. Genes located on the long arm of chicken chromosome 3 remain together on a single chromosome in the devil, a species with a conserved 2n = 14 chromosome complement, but has been subject to independent fission events to distribute these genes across two chromosomes in the wallaby and opossum. Lines have been drawn between chromosomes to reflect changes in gene order. Vertical bars indicate conserved blocks of genes. Modified from Deakin (2012).
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Diversification of Plants and Animals | Evolutionary Genomics
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Article Title: Genome Sequence of an Australian Kangaroo, Macropus eugenii
 
How to Cite close
Deakin, Janine E(Mar 2013) Genome Sequence of an Australian Kangaroo, Macropus eugenii. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0023980]