Blue light and its receptor white collar complex (FfWCC) regulates mycelial growth and fruiting body development in Flammulina filiformis

Light is a common environmental factor in nature, which was often used in Flammulina filiformis industrialized cultivation. In this study, we identified white collar photoreceptor (FfWc1 and FfWc2) with conserved PAS domain in F. filiformis. The results of the overall light treatment showed that the transcription levels of FfWc1 and FfWc2 reached the peak under the blue light with 3 symbolscript symbolscript 1 intensity, and increased by 3.3-fold and 10.1 -fold, respectively, at 3 h after the blue light irradiation. During the fruiting body development of F. filiformis, FfWc1 and FfWc2 were significantly up-regulated with the formation of primordia and the rapid elongation of the stipe (around day 8 after primordia formation). Further, we performed the knockdown and overexpression of FfWc1/FfWc2, the results showed that aerial mycelia became denser, the number of fruiting body increased, and the length of the stipe increased in the FfWc1/FfWc2 overexpression strains, while the opposite results were found in the FfWc1/FfWc2 knockdown strains. In addition, total nine genes encoding cell wall-related enzymes, including exo-beta-1, 3-glucanase, beta-1, 6-glucan synthase and chitinase, were up-regulated with varying degrees in FfWc1/FfWc2 overexpression strains, seven of them (except for two chitinases) were down-regulated in FfWc1/ FfWc2 knockdown strains. It suggested that WC may regulate the growth morphology of mycelia and the elongation rate of fruiting body by acting on these cell wall-related enzyme genes, and then affect the morphological development of F. filiformis. The results clearly demonstrate the significant changes in the fruiting body morphology of F. filiformis under the partial loss or increase of WC function, and have guiding significance for scientific use of blue light to regulate the commodity characters of mushroom.