Transposable Element Mobilization in Interspecific Yeast Hybrids.

Area of Science:

• Genetics
• Molecular Biology
• Yeast Genetics

Background:

• Barbara McClintock's "genomic shock" hypothesis suggests interspecific hybridization mobilizes transposable elements (TEs) by disrupting their regulation.
• Previous studies on this hypothesis have produced inconsistent results.
• The regulation of Ty elements (a type of TE) in Saccharomyces uvarum and their loss in this species remain poorly understood.

Purpose of the Study:

• To investigate if hybridization increases TE transposition rates and facilitates TE colonization in Saccharomyces cerevisiae × Saccharomyces uvarum hybrids.
• To determine if Ty elements can insert into the S. uvarum genome within hybrids.
• To directly measure transposition rates in hybrids and assess the impact of hybridization and mitochondrial inheritance.

Main Methods:

• Inducing transposition in yeast hybrids (S. cerevisiae × S. uvarum).
• Developing a sequencing technique to detect TE insertions in the S. uvarum sub-genome.
• Utilizing an in vivo reporter construct to quantify transposition rates.

Main Results:

• Ty elements readily insert into the S. uvarum genome within hybrids, exhibiting non-random insertion patterns.
• Hybridization itself does not alter the rate of Ty element mobilization.
• Species-specific mitochondrial inheritance was found to significantly alter transposition rates, by up to an order of magnitude.

Conclusions:

• Hybridization can facilitate the introduction of TEs across species boundaries.
• Mitochondrial transmission plays a crucial role in modulating TE transposition rates.
• The "genomic shock" theory's prediction of unrestrained TE proliferation following hybridization is not supported by these findings.