PhD defence: Yang Zhou

Monotreme Genomes Provide Insights into the Evolution of Early Mammal and Monotreme Sex Chromosomes System

Supervisor
Professor Guojie Zhang, Section for Ecology and Evolution, UCPH

Examiners
Anders Albrechtsen (Chair), Wen Wang, and Xin Zhou

Abstract
Egg-laying mammals Ornithorhynchus anatinus and Tachyglossus aculeatus harbor many primitive characters of mammals as well as a complex multiple sex chromosome system. Although platypus genome has been published a decade ago, the assembly quality is relatively poor which hinder us from deeper understanding of the evolution of early mammals and sex chromosome system. Here we utilized multiple types of technologies and performed extensive curation to obtain a chromosome-level male platypus assembly with great improvement, and the first male echidna assembly where most X-linked sequences anchored onto chromosomes. These new monotremes assemblies enable us to reconstruct mammalian ancestral karyotype for the first time, revealing mammalian evolution in a macro view. Moreover, these male assemblies also provided detailed evolutionary trajectory of monotreme sex chromosome evolution and revealed an unexpected interchromosomal interaction among sex chromosomes. In addition, the comparison between platypus and echidna also revealed some molecular basis of the adaptation to their different ecological niches.