Mating System of Coprinus comatus

Abstract

Coprinus comatus is known to be a phylogenetically diverse species and multiple mating types have been reported; thus, it is necessary to reconsider the mating system of Japanese C. comatus. Our phylogenetic analysis, based on the ITS region, revealed that this species could be divided into three clades, and Japanese C. comatus was placed into a single clade. Homokaryons isolated from the fruiting body of C. comatus showed that the mating system was bipolar heterothallism. No A incompatibility factor recombinant was found, suggesting that factor A is composed of two extremely close subunits on the same chromosome. On the other hand, heterokaryons and homokaryons can be distinguished by the frequency of clamp formation. The frequency of clamp formation in heterokaryons was 30% or more, while that of homokaryons was 8% or less. Moreover, it was suggested that the ability to form clamp cells in the homokaryons was not genetically linked to mating-type locus.