CmLec4, a lectin from the fungus Cordyceps militaris, controls host infection and fruiting body formation.

Fungi belonging to the Ascomycete genus Cordyceps are endoparasitoids and parasites, mainly of insects and other arthropods. Cordyceps militaris has been used as a therapeutic drug for cancer patients. However, the infection, parasitism, and fruiting body formation mechanisms of this fungus are still unknown. Based on our hypothesis that lectin(s) is involved in the interaction between the C. militaris fungi and insects, we partially purified and characterized a new lectin from C. militaris, designated CmLec4. In addition, we searched for substance(s) in the infected silkworm extracts that could bind to CmLec4, and succeeded in purifying the sex-specific storage protein 2 as a specific binding target. To examine function of the binding protein during the process of parasitism, we investigated the effect of recombinant CmLec4 on silkworms by inoculating the protein into silkworm pupae, and found that it significantly delayed emergence compared to the control. Furthermore, cmlec4 gene knockout strains constructed in this study produced markedly lower amounts of fruiting body than the wild-type strain. All the results revealed that the lectin CmLec4 produced by C. militaris would be involved in the infection into silkworm and fruiting body formation from the host.

Genome Sequence of a Novel Iflavirus from mRNA Sequencing of the Pupa of Bombyx mori Inoculated with Cordyceps militaris.

We discovered a novel iflavirus from the transcriptome of the Bombyx mori pupa inoculated with the insect-pathogenic fungus Cordyceps militaris. The assembled iflavirus genome has 10,119 nucleotides, with a 3'-polyadenylated tail, and it encodes a polyprotein composed of 3,004 amino acids.