Blue light receptor cryptochrome determines primordia formation, fruiting body development and pileus opening in macro mushroom Flammulina filiformis

Blue light, as a crucial environmental factor, can regulate the morphological development of macro fungi. The receptor WCC (white collar complex) has been found to play a role in controlling fruiting body elongation, but another important receptor, cryptochrome, was easily overlooked its important role. In this study, we investigated the overall impacts of cryptochrome gene (FfCry) knockdown on the morphological development of fruiting bodies and its downstream regulation of metabolic activities in Flammulina filiformis. Two knockdown strains FfCry-kd8 and FfCry-kd13 were constructed to explore the morphological changes after FfCry knockdown. The results showed that the number of primordia of FfCry-kd8 and FfCry-kd13 was reduced by 33.6 % and 38.0 %. Obviously, FfCry-kd8 and FfCry-kd13 showed much shorter and finer stipes (With stipe lengths reduced by 51.8 % and 55.1 %, and stipe diameters by 43.4 % and 34.6 %), compared with wild type (WT). Especially, two FfCry-kd transformants showed much smaller pileus than WT (diameter was decreased by 52.6 % and 55.9 %), meaning that FfCry knockdown inhibited the pileus opening. RNA Sequencing (RNA-Seq) analysis identified that 216 genes were up-regulated and 164 genes were down-regulated after FfCry knockdown. The FfCry gene knockdown primarily activated the glucan 1,3-β-glucosidase, peptide receptor, and β-alanine metabolic pathways; while mainly inhibiting starch and sucrose metabolism, as well as various N-polymer biosynthesis and sphingolipid metabolism, etc. These metabolic pathways played important roles in the formation of cell walls and the fluidity of cell membranes. The results clearly demonstrate the significant changes in the fruiting body morphology of F. filiformis in the case of partial loss of FfCry function. This finding holds guiding significance for the scientific utilization of blue light to regulate the commercial characteristics of mushrooms.