Infection Process and Genome Assembly Provide Insights into the Pathogenic Mechanism of Destructive Mycoparasite Calcarisporium cordycipiticola with Host Specificity

Abstract

Calcarisporium cordycipiticola is the pathogen in the white mildew disease of Cordyceps militaris, one of the popular mushrooms. This disease frequently occurs and there is no effective method for disease prevention and control. In the present study, C. militaris is found to be the only host of C. cordycipiticola, indicating strict host specificity. The infection process was monitored by fluorescent labeling and scanning and transmission electron microscopes. C. cordycipiticola can invade into the gaps among hyphae of the fruiting bodies of the host and fill them gradually. It can degrade the hyphae of the host by both direct contact and noncontact. The parasitism is initially biotrophic, and then necrotrophic as mycoparasitic interaction progresses. The approximate chromosome-level genome assembly of C. cordycipiticola yielded an N50 length of 5.45 Mbp and a total size of 34.51 Mbp, encoding 10,443 proteins. Phylogenomic analysis revealed that C. cordycipiticola is phylogenetically close to its specific host, C. militaris. A comparative genomic analysis showed that the number of CAZymes of C. cordycipiticola was much less than in other mycoparasites, which might be attributed to its host specificity. Secondary metabolite cluster analysis disclosed the great biosynthetic capabilities and potential mycotoxin production capability. This study provides insights into the potential pathogenesis and interaction between mycoparasite and its host.

Dual Transcriptomics Reveals Interspecific Interactions between the Mycoparasite Calcarisporium cordycipiticola and Its Host Cordyceps militaris

“…S3A and Table S4). Among 189 effectors predicted in the genome of C. cordycipiticola ( 16 ), 89 were differentially expressed at 4 or 8 dpi compared with CC (Table S4), among which 76.4% (68/89) were significantly upregulated (Fig. S3B and Table S4).…”

“…Among the 441 predicted genes encoding carbohydrate-active enzymes (CAZymes) in the genome of C. cordycipiticola ( 16 ), 213 (48%) were differentially expressed at 4 or 8 dpi compared with CC (Table S10). The genes were grouped into three main clusters according to their expression patterns ( Fig.…”

“…is an important edible and medicinal fungus, and its annual value has increased year by year, reaching 10 billion renminbi in China in 2016 ( 14 ). However, fungal diseases have become one of the bottlenecks in the large-scale production of fruiting bodies, among which white mildew disease caused by Calcarisporium cordycipiticola has been the most destructive and has resulted in huge economic losses to the C. militaris industry in China ( 15 , 16 ). There has been no effective prevention and control method until now.…”

“…The hyphae of C. cordycipiticola can invade the gaps among hyphae of the fruiting bodies of C. militaris and fill them gradually. They can degrade the hyphae of the host by both direct contact and noncontact ( 16 ). The parasitism is initially biotrophic and then necrotrophic as the mycoparasitic interaction progresses ( 16 ).…”

“…They can degrade the hyphae of the host by both direct contact and noncontact ( 16 ). The parasitism is initially biotrophic and then necrotrophic as the mycoparasitic interaction progresses ( 16 ). Beyond that, there had been no information on the pathogenic mechanism of C. cordycipiticola (pathogen) and the mechanism of the response of C. militaris (host), which is crucial for disease prevention and control.…”