Evolution of a bipolar sexual compatibility system in Marasmius

Area of Science:

• Mycology
• Evolutionary Biology
• Genetics

Background:

• Basidiomycota sexual compatibility relies on one or two loci (HD and P/R).
• Bipolar mating systems can arise from locus linkage or loss of mating-type determination.
• The ancestral basidiomycete mating system is presumed tetrapolar, with documented transitions to bipolarity.

Purpose of the Study:

• Investigate the evolutionary origin of bipolar mating systems in the genus Marasmius.
• Determine the mode of bipolarity evolution within Marasmius.
• Analyze the genomic architecture and nucleotide diversity of mating-type loci in Marasmius.

Main Methods:

• Phylogenetic analysis using concatenated multilocus sequence data.
• Genomic data analysis of Marasmius oreades.
• Comparison of nucleotide diversity at HD and P/R loci.

Main Results:

• Phylogenetic analysis supports a single evolutionary transition to bipolar mating in Marasmius.
• The HD and P/R loci remained unlinked during the evolution of bipolarity in Marasmius.
• The HD locus exhibits high nucleotide diversity, suggesting its role in maintaining sexual identity.

Conclusions:

• Bipolar mating systems in Marasmius likely evolved once from a tetrapolar ancestor.
• The transition to bipolarity in Marasmius involved unlinked mating-type loci.
• The HD locus plays a crucial role in sexual compatibility determination in bipolar Marasmius species.