Genome Analysis of Hypomyces perniciosus, the Causal Agent of Wet Bubble Disease of Button Mushroom (Agaricus bisporus)

Abstract

The mycoparasitic fungus Hypomyces perniciosus causes wet bubble disease of mushrooms, particularly Agaricus bisporus. The genome of a highly virulent strain of H. perniciosus HP10 was sequenced and compared to three other fungi from the order Hypocreales that cause disease on A. bisporus. H. perniciosus genome is ~44 Mb, encodes 10,077 genes and enriched with transposable elements up to 25.3%. Phylogenetic analysis revealed that H. perniciosus is closely related to Cladobotryum protrusum and diverged from their common ancestor ~156.7 million years ago. H. perniciosus has few secreted proteins compared to C. protrusum and Trichoderma virens, but significantly expanded protein families of transporters, protein kinases, CAZymes (GH 18), peptidases, cytochrome P450, and SMs that are essential for mycoparasitism and adaptation to harsh environments. This study provides insights into H. perniciosus evolution and pathogenesis and will contribute to the development of effective disease management strategies to control wet bubble disease.

Genomic Features of Cladobotryum dendroides, Which Causes Cobweb Disease in Edible Mushrooms, and Identification of Genes Related to Pathogenicity and Mycoparasitism

“…However, sequenced genomes in this genus (Hypomyces/Cladobotryum) are scarce. To date, only the genomes of C. protrusum and H. perniciosa (the sexual morph of M. perniciosa) have been released [17,18]. C. protrusum is the only species of Cladobotryum for which a genome is available [17].…”

“…Associated advances have improved the identification of pathogenicity-related genes and revealed the molecular mechanisms underlying pathogenesis. To date, several pathogenic genomes have been sequenced using Pacific Biosciences (PacBio) Sequel or the RSII platform [17,18,20]. With these available genomic sequences, it is possible to determine the evolutionary relationships among fungi [21][22][23][24], as well as to explore the evolution of nutritional mode.…”

Genetic and Pathogenic Variability of Mycogone perniciosa Isolates Causing Wet Bubble Disease on Agaricus bisporus in China

“…For example, Fletcher et al [4] reported that non-pigmented white isolates of M. perniciosa are less pathogenic than the pigmented isolates. The moderate to high virulence levels of the yellow to brown M. perniciosa isolates may be due to a large amount of conidia production, and production of secondary metabolites (e.g., pigments and mycotoxins) plays an important role in pathogenesis [12,19]. In contrast, Fletcher et al [4] reported that the less aggressiveness of some of the isolates maybe as a result of mycovirus infecting those strains.…”

“…Mutation, gene flow, sexual reproduction (recombination) and the adaptation to diverse fungal hosts might have contributed to the genetic diversity of M. perniciosa from the AFLP analysis. In our previous work [12], the analysis of the genome sequence of M. perniciosa (Hp 10) revealed it is heterothallic species containing MAT 1-2 locus. There is a need for further studies to identify the sexual stages of the isolates to find out whether the sexual stage contributes to the diversity of this pathogen [26].…”

“…The minimum incubation period was 2-3 days for all isolates on the highly susceptible A. bisporus strains and those for highly resistant A. bisporus strains required a maximum incubation period of five days. The wet bubble disease symptoms on A. bisporus include malformation of basidiome, white, fluffy mycelial growth, copious amber droplets, and flocculent mycelia on most substrates [12]. All the isolates produced typical wet bubble disease symptoms with different levels of symptom severity depending on all the A. bisporus strains tested.…”