| Summary: | True morels (<i>Morchella</i> spp.) are a group of delicious fungi in high demand worldwide, and some species of morels have been successfully cultivated in recent years. To better understand the sexual reproductive mechanisms of these fungi, we characterized the structure of the mating-type loci from ten morel species, and seven of them were obtained using long-range PCR amplification. Among the studied species, eight were heterothallic, two were homothallic, and four types of composition were observed in the <i>MAT</i> loci. In three of the five black morel species, the <i>MAT1-1-1</i>, <i>MAT1-1-10</i>, and <i>MAT1-1-11</i> genes were in the <i>MAT1-1</i> idiomorph, and only the <i>MAT1-2-1</i> gene was in the <i>MAT1-2</i> idiomorph, while an integration event occurred in the other two species and resulted in the importation of the <i>MAT1-1-11</i> gene into the <i>MAT1-2</i> idiomorph and survival as a truncated fragment in the <i>MAT1-1</i> idiomorph. However, the <i>MAT1-1-11</i> gene was not available in the four yellow morels and one blushing morel species. <i>M. rufobrunnea</i>, a representative species of the earliest diverging branch of true morels, along with another yellow morel <i>Mes-15</i>, were confirmed to be homothallic, and the <i>MAT1-1-1</i>, <i>MAT1-1-10</i>, and <i>MAT1-2-1</i> genes were arranged in a tandem array. Therefore, we hypothesized that homothallism should be the ancestral reproductive state in <i>Morchella.</i> RT-PCR analyses revealed that four mating genes could be constitutively expressed, while the <i>MAT1-1-10</i> gene underwent alternative splicing to produce different splice variants.
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