A Genetic Linkage Map and Improved Genome Assembly of the Termite Symbiont Termitomyces cryptogamus

Author: mycolabadmin
2023-03-16
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Summary

This research provides new insights into the genetic structure and evolution of an important symbiotic fungus that lives in partnership with termites. The study reveals how this fungus maintains genetic diversity while living in a stable environment inside termite nests. Impacts on everyday life: • Helps understand how beneficial partnerships between different species remain stable in nature • Contributes to knowledge about fungi that are important food sources in many regions • Advances our understanding of termite biology, which is relevant for pest control • Demonstrates improved methods for studying complex genetic systems • Provides insights that could help develop better sustainable agricultural practices

Background

The termite-fungus symbiosis is an ancient stable mutualism between two partners that reproduce and disperse independently. With each new termite colony, the symbiotic association must be re-established with a new fungus partner. The stability of this symbiosis despite horizontal symbiont transmission may be due to complementarity in plant substrate breakdown ability or potentially a reduced rate of evolution known as the Red King Effect.

Objective

To explore the concept of reduced evolution rate in symbiotic relationships by producing the first linkage map of a Termitomyces species using genotyping by sequencing of homokaryotic offspring, and constructing a highly contiguous genome assembly to examine the recombination landscape and its potential effect on the mutualistic lifestyle.

Results

The linkage map resulted in a genome-wide recombination rate of 22 cM/Mb, which was lower than that of other related fungi. However, the total map length of 1370 cM was similar to other related fungi. The improved genome assembly consisted of 64 contigs with a total length of 70 Mb, showing significantly better contiguity than the previous version. The study revealed that T. cryptogamus has a bipolar mating system and identified regions of both high and low recombination rates across the genome.

Conclusion

The apparently decreased rate of recombination in Termitomyces cryptogamus is primarily due to genome expansion of islands of gene-poor repetitive sequences rather than an actual reduction in recombination events. The total genetic map length is comparable to free-living fungi, suggesting that this symbiotic species has not evolved reduced recombination rates as might be expected for inhabitants of stable mutualisms.

Published in:BMC Genomics,
Study Type:Genomic Analysis,
Source: 10.1186/s12864-023-09210-x