The Fvclp1 gene regulates mycelial growth and fruiting body development in edible mushroom Flammulina velutipes

Fruiting body development in Agaricomycetes represents the most complex and unclear process in the fungi. Mating type pathways (A and B) and transcription factors are important regulators in the sexual development of mushrooms. It is known that clampless1 (clp1) is an additional gene that participate under the homeodomain (HD) genes in the matA pathway and clp1 inactivation blocks clamps formation in Coprinopsis cinerea. In this study we identified and analyzed a homologous Fvclp1 gene in the edible mushroom Flammulina velutipes. The coding sequence of the Fvclp1 was 1011 bp without intron interruption, encoding a protein of 336 amino acids. To exhibit the role of Fvclp1 in clamp development and fruiting body formation, knockdown and overexpression mutants were prepared. No significant difference was observed in the monokaryotic hyphal morphology of overexpression and knockdown transformants. In the dikaryotic hyphae from the compatible crossings between the wild-type L22 strain and Fvclp1 knockdown or overexpression mutants, clamp connections developed. However, knockdown mutants could generate fewer fruiting bodies than the wild-type strain. On the contrary, reduced mycelial growth rate but improved fruiting ability was observed in the dikaryotic Fvclp1 overexpression mutants as compared to the wild-type strain. These results indicate that Fvclp1 is necessary and actively involved in fruiting body development in F. velutipes. Overall, these findings suggest that further studies on the function of Fvclp1 would advance our understanding of sexual reproduction and fruiting body development in edible mushrooms.