Identification, characterization and expression of A-mating type genes in monokaryons and dikaryons of the edible mushroom Mycoleptodonoides aitchisonii (Bunaharitake)

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Identifying the mating-type in Mycoleptodonoides aitchisonii is important for enhancing breeding and cultivation of this edible mushroom. To clarify the molecular mechanisms of the bipolar mating system in M. aitchisonii, the homeodomain protein gene 2 (Mahd2) was characterized. A genomic DNA fragment of Mahd2 in M. aitchisonii 50005-18 strain was 1,851 bp long and encoded a protein of 614 amino acids. Transcriptional analysis revealed that the expression of Mahd2 was higher in monokaryotic strains that produced clamp cells than in those that did not. The highest relative expression level of Mahd2 was observed in monokaryon TUFC 50005-4, which was capable of forming a true clamp. These results suggested that the formation of clamp cells is regulated by A-mating type homeodomain proteins, and the frequency of clamp cell formation might be promoted by high expression of the Mahd2 gene.