Near-Complete De Novo Assembly of Tricholoma bakamatsutake Chromosomes Revealed the Structural Divergence and Differentiation of Tricholoma Genomes

Summary

This research provides the first detailed genetic blueprint of Tricholoma bakamatsutake, an economically important edible mushroom that grows in symbiosis with oak and related trees. The study reveals how this mushroom’s genetic makeup differs from its close relative, the prized matsutake mushroom, despite sharing similar basic chromosome structures. This understanding is crucial for conservation and potentially cultivation efforts. Impacts on everyday life: • Helps understand why certain mushrooms only grow with specific trees, which is important for forest management • Could lead to improved cultivation methods for valuable edible mushrooms • Contributes to conservation efforts of economically important wild mushrooms • May help develop better ways to identify different mushroom species in the wild

Background

Tricholoma bakamatsutake is an edible ectomycorrhizal fungus that forms symbiotic relationships with Fagaceae trees. It is believed to have diverged before other species in the Tricholoma section Caligata. Unlike its relative T. matsutake which associates with Pinaceae trees, T. bakamatsutake colonizes the A0 soil layer containing litter in both deciduous and evergreen broad-leaved forests.

Objective

The study aimed to generate and analyze a highly contiguous whole-genome sequence for T. bakamatsutake SF-Tf05 isolated from an Oak forest in Japan, to better understand the evolution and differentiation of Tricholoma species.

Results

The assembly resulted in 13 chromosome-sized contigs comprising 142,068,211 bases with an average GC content of 43.94%. The chromosomes were predicted to encode 11,060 genes. A circular mitochondrial genome contig of 122,566 bases was also recovered. While the basic number of chromosomes (13) was conserved between T. bakamatsutake and T. matsutake, their chromosome structures showed significant divergence with multiple inversions and translocations. The analysis revealed at least 3 phylogenetic clades in Tricholoma section Caligata, with T. bakamatsutake strains forming a distinct ‘bakamatsutake’ clade.

Conclusion

The study successfully constructed a highly contiguous near telomere-to-telomere genome sequence of T. bakamatsutake, providing a fundamental resource for future research on Tricholoma species evolution and differentiation. The findings revealed significant structural divergence between T. bakamatsutake and T. matsutake genomes, despite conservation in chromosome number.
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