Multiple molecular mechanisms cause reproductive isolation between three yeast species

Area of Science:

• Evolutionary Biology
• Genetics
• Molecular Biology

Background:

• Nuclear-mitochondrial conflict, or cytonuclear incompatibility, is a known driver of reproductive isolation.
• Previous studies demonstrated this incompatibility in yeast species.

Purpose of the Study:

• To identify new incompatible genes contributing to F2 hybrid sterility in Saccharomyces species.
• To investigate the evolutionary mechanisms of cytonuclear incompatibility.

Main Methods:

• Systematic study of F2 hybrid sterility in three Saccharomyces species.
• Molecular analyses of nuclear genes MRS1 and AIM22.
• Functional complementation assays.

Main Results:

• Identified MRS1 and AIM22 as new incompatible genes.
• Found evidence of coevolution between MRS1 and mitochondrial COX1 introns.
• Determined three nonsynonymous mutations in MRS1 are responsible for functional differences.
• Observed a strong correlation between phylogeny and the evolution of cytonuclear incompatibility.

Conclusions:

• Nuclear-mitochondrial incompatibility, driven by genes like MRS1 and AIM22, is a significant mechanism for reproductive isolation in yeast.
• Coevolution and specific mutations play key roles in the emergence of cytonuclear incompatibility.