Single nucleus sequencing reveals evidence of inter-nucleus recombination in arbuscular mycorrhizal fungi

Elife. 2018 Dec 5;7:e39813. doi: 10.7554/eLife.39813.

Abstract

Eukaryotes thought to have evolved clonally for millions of years are referred to as ancient asexuals. The oldest group among these are the arbuscular mycorrhizal fungi (AMF), which are plant symbionts harboring hundreds of nuclei within one continuous cytoplasm. Some AMF strains (dikaryons) harbor two co-existing nucleotypes but there is no direct evidence that such nuclei recombine in this life-stage, as is expected for sexual fungi. Here, we show that AMF nuclei with distinct genotypes can undergo recombination. Inter-nuclear genetic exchange varies in frequency among strains, and despite recombination all nuclear genomes have an average similarity of at least 99.8%. The present study demonstrates that AMF can generate genetic diversity via meiotic-like processes in the absence of observable mating. The AMF dikaryotic life-stage is a primary source of nuclear variability in these organisms, highlighting its potential for strain enhancement of these symbionts.

Keywords: S. cerevisiae; arbuscular mycorrhizal fungi; evolutionary biology; genetics; genomics; meiosis; recombination; sexual reproduction; single nucleus sequencing.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Cell Nucleus / genetics*
  • Cell Nucleus / ultrastructure
  • Cytoplasm / genetics
  • Cytoplasm / ultrastructure
  • DNA, Fungal / genetics*
  • Genetic Variation
  • Genome, Fungal*
  • Genotype
  • Mycorrhizae / genetics*
  • Plants / microbiology
  • Polymorphism, Single Nucleotide
  • Recombination, Genetic*
  • Sequence Analysis, DNA
  • Symbiosis

Substances

  • DNA, Fungal

Grant support

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.