Evolutionary genomics of transposable elements in Saccharomyces cerevisiae

Area of Science:

• Genomics
• Evolutionary Biology
• Molecular Biology

Background:

• Saccharomyces cerevisiae is a key model for studying transposable elements (TEs).
• Previous studies on Ty element families (Ty1-Ty5) in S. cerevisiae benefited from genome availability.
• Advances in bioinformatics and yeast genomics necessitate new investigations into Ty evolution.

Purpose of the Study:

• To conduct a comprehensive phylogenetic and population genetic analysis of all Ty families in S. cerevisiae.
• To re-annotate Ty elements in the S288c reference genome and identify novel TE families.
• To investigate the evolutionary dynamics and origins of Ty elements in S. cerevisiae.

Main Methods:

• Systematic re-annotation of Ty elements in the S288c reference genome.
• Phylogenetic analysis of Long Terminal Repeat (LTR) sequences from Ty elements.
• Population genomic analysis using data from 38 additional S. cerevisiae strains.
• Comparative genomic analysis to infer horizontal transfer events.

Main Results:

• Underestimated copy numbers for all known Ty element families were identified.
• A new family of Ty3-like elements, composed of degenerate solo LTRs, was discovered.
• Phylogenetic analyses revealed varying activity levels across Ty families (Ty1, Ty2, Ty3, Ty4, Ty3p, Ty5).
• Population genomic data indicated most S288c Ty insertions are fixed, with active clades being polymorphic and inactive ones fixed.
• Evidence suggests horizontal transfer as the origin for Ty2 and Ty3p families in the S. cerevisiae genome.

Conclusions:

• A single individual's genome provides insights into species-wide TE population dynamics.
• Horizontal transfer may significantly contribute to the genomic diversity of TEs in unicellular eukaryotes.
• This study refines our understanding of Ty element evolution and population dynamics in S. cerevisiae.