Examining the genetics of mushroom development in the cultivated edible mushroom Flammulina velutipes

Abstract

Flammulina velutipes is a cultivated edible mushroom with two distinct growth forms: highly pigmented and umbrella-shaped in the wild, but pale and thread-like under cultivation conditions. Recent studies using F. velutipes to study gene expression changes during mushroom development have largely ignored tissue-level differences and the normal (wild) growth form. The present study extracted and sequenced F. velutipes mRNA from four tissues (mycelium, stipe, pileus, and gills) at four growth stages (primordia, young mushrooms, mature cultivated mushrooms, and mature normal mushrooms) to assemble a transcriptome of 20,909 transcripts from 14,416 potential genes. Analyses identified 2,183 differentially expressed genes (q < 0.05), 1,456 of which matched named proteins in the UniProtKB Agaricales database. Tissue had a much larger impact on gene expression than growth stage did and analysis revealed a stipe-specific hydrophobin (UniProtKB accession G8A517), four stipe-specific cytochrome p450 genes, and one cytochrome p450 specific to the pileus and gills. Genes previously known to be involved in the fruiting process (including fds, fvfd16, MAPK, and WD40 repeat- containing genes) tended to be most highly expressed in actively growing tissues, suggesting that regulating cell growth is a key mechanism during mushroom formation. These results augment existing knowledge of developmental genetics of mushroom- forming fungi.