A hydrophobin gene, Hyd9, plays an important role in the formation of aerial hyphae and primordia in Flammulina filiformis.

Flammulina filiformis is an edible fungus that is largely cultivated and widely consumed around the world. The quantity and quality of the primordia, which gives rise to the fruiting body, affects its production efficiency. Hydrophobins are involved in the formation of the fruiting body of macrofungi. However, functional verification of the hydrophobin genes is limited to date. In this study, we used gene silencing and overexpression analyses to investigate the function of one F. filiformis hydrophobin gene (Hyd9) during the development of the fruiting body. The Hyd9-silenced transformants exhibited sparse aerial hyphae, resulting in fewer primordia and fruiting bodies. In contrast, the Hyd9 overexpression strain displayed denser aerial hyphae and more primordia. The phenotypes of these transgenic lines strongly suggested that Hyd9 plays an important role in the formation of aerial hyphal knots (the primary stage of primordia) and primordia in F. filiformis. These results will be beneficial for developing more efficient methods to induce primordia formation in F. filiformis and other commercially valuable mushrooms.