Genome reduction and relaxed selection is associated with the transition to symbiosis in the basidiomycete genus Podaxis

Benjamin H. Conlon*, Cene Gostinčar, Janis Fricke, Nina B. Kreuzenbeck, Jan Martin Daniel, Malte S.L. Schlosser, Nils Peereboom, Duur K. Aanen, Z.W. de Beer, Christine Beemelmanns, Nina Gunde-Cimerman, Michael Poulsen

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Insights into the genomic consequences of symbiosis for basidiomycete fungi associated with social insects remain sparse. Capitalizing on viability of spores from centuries-old herbarium specimens of free-living, facultative, and specialist termite-associated Podaxis fungi, we obtained genomes of 10 specimens, including two type species described by Linnaeus >240 years ago. We document that the transition to termite association was accompanied by significant reductions in genome size and gene content, accelerated evolution in protein-coding genes, and reduced functional capacities for oxidative stress responses and lignin degradation. Functional testing confirmed that termite specialists perform worse under oxidative stress, while all lineages retained some capacity to cleave lignin. Mitochondrial genomes of termite associates were significantly larger; possibly driven by smaller population sizes or reduced competition, supported by apparent loss of certain biosynthetic gene clusters. Our findings point to relaxed selection that mirrors genome traits observed among obligate endosymbiotic bacteria of many insects.

Original languageEnglish
Article number102680
JournaliScience
Volume24
Issue number6
DOIs
Publication statusPublished - 25 Jun 2021

Keywords

  • Biological sciences
  • Genetics
  • genomics

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