MYCOLab Ai Logo - gold and army green

Genetic differentiation in the MAT-proximal region is not sufficient for suppressing recombination in Podospora anserina

Summary

Scientists studied why certain regions of fungal chromosomes don’t allow genetic recombination like normal chromosomes do. By creating a mutant fungus where a previously different genetic region became identical, they found that genetic differences alone don’t explain why recombination stops. Instead, they discovered that other biological mechanisms, possibly involving chemical modifications to DNA or special regulatory proteins, must be responsible for preventing genetic mixing in these special chromosome regions.

Background

Recombination suppression has evolved repeatedly in sex and mating-type chromosomes, but the evolutionary causes and proximal mechanisms are poorly understood. In the ascomycete fungus Podospora anserina, a 0.8-Mbp nonrecombining region exists around the mating-type locus despite being collinear between the two mating types, suggesting mechanisms other than inversions.

Objective

To test the hypothesis that sequence divergence alone is responsible for recombination suppression in the mating-type proximal region of P. anserina. The study investigated whether replacing the mat− idiomorph with mat+ sequence would restore recombination in isogenic strains.

Results

Recombination remained suppressed in the MAT-proximal region even when the region was made homozygous, with only 1 recombination event detected in 221 offspring (0.45%) compared to expected rates of 3.75% in control crosses. Sequencing confirmed the successful replacement of the MAT locus without affecting chromosomal structure.

Conclusion

Sequence divergence alone is not responsible for recombination suppression in P. anserina, indicating that other proximal mechanisms such as trans-acting factors or epigenetic marks are involved. The findings suggest selective mechanisms or epigenetic regulation rather than neutral divergence drive recombination suppression in fungal mating-type chromosomes.
  • Published in:G3 (Bethesda),
  • Study Type:Experimental Study,
  • Source: PMID: 39849944, DOI: 10.1093/g3journal/jkaf015
Scroll to Top