Pervasive gene conversion in chromosomal inversion heterozygotes

Area of Science:

• Genetics
• Evolutionary Biology
• Molecular Biology

Background:

• Chromosomal inversions influence genome recombination and can reduce gene flow between species.
• Noncrossover gene conversion can mitigate the recombination barrier imposed by inversions.

Purpose of the Study:

• To empirically analyze genomewide gene conversion rates within species and in species hybrids.
• To assess the role of gene conversion in overcoming inversion-mediated reproductive isolation.

Main Methods:

• Experimental crosses within Drosophila pseudoobscura and between D. pseudoobscura and D. persimilis.
• Genomewide empirical analysis of gene conversion rates.
• Estimation of gene conversion rates per base pair per generation.

Main Results:

• Gene conversion rates range from 1 x 10^-5 to 2.5 x 10^-5 converted sites per bp per generation.
• Gene conversion rates in hybrids are as high as or higher than within-species rates.
• Gene conversion occurs within and around inverted regions, even near breakpoints, and can be mitotic or meiotic.
• Gene conversion rates are higher in regions of lower sequence divergence but remain substantial in more divergent inverted regions.

Conclusions:

• Gene conversion actively occurs within chromosomal inversions in species hybrids.
• High gene conversion rates can counteract the barrier to recombination imposed by inversions.
• Gene conversion has the potential to reduce the efficacy of inversions as barriers to gene flow over evolutionary time.