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.

Heterologous expression of a lectin from Pleurocybella porrigens (PPL) in Phanerochaete sordida YK-624.

Pleurocybella porrigens is a mushroom-forming fungus, which had been consumed as a traditional food in Japan. However, in 2004, 55 people got poisoned by eating the mushroom and 17 people among them died of acute encephalopathy. We have already reported the purification, characterization, and cDNA cloning of a lectin from the mushroom (PPL) which might have caused the poisoning. Here, we report the heterologous expression of recombinant PPL by basidiomycete Phanerochaete sordida YK-624. The glyceraldehyde 3-phosphate dehydrogenase gene promoter was used to drive the expression of the PPL gene (ppl) in P. sordida YK-624. Furthermore, the signal peptide of lignin peroxidase which is an extracellular protein was used to secrete rPPL into extracellular region. Fifteen regenerated clones were cultured on Kirk HNHC broth, and the presence of lectin activity in the culture broth was checked by agglutination assays. The results indicated that the culture broth of rPPL-6 clone showed the strongest hemagglutination activity, and it was therefore used for subsequent analysis. The heterologous expression of rPPL by P. sordida YK-624 was confirmed by SDS-PAGE, lectin activity by the hemagglutination assay, and mass of rPPL by MALDI-TOF respectively, indicating that the extracellular secretion of rPPL as active form was successful.