[Maturation of Cordyceps sinensis associates with alterations of fungal expressions of multiple Ophiocordyceps sinensis mutants in stroma of Cordyceps sinensis].

Objective: To examine maturational changes in expressions of Ophiocordyceps sinensis (O.sinensis) transition and transversion mutation genotypes in Cordyceps sinensis (C.sinensis) stroma.

Methods: MassARRAY single nucleotide polymorphism (SNP) matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrum genotyping was used, and 8 SNP extension primers were designed based on the scattered, multiple point mutations of known sequences for the O.sinensis mutants within their internal transcribed spacer (ITS) segments. Of the extension primers, 5 (not capable of distinguishing between the 2 AT-biased genotypes) located in rDNA ITS1 and ITS2 regions: 067721-211, 067721-240, 067721-477, 067721-531 and 067721-581. The other 3 extension primers located in 5.8S rDNA region: 067740-324, 067740-328 and 067740-360, to distinguish between the 2 AT-biased genotypes.

Results: MS chromatograms at the 8 SNP sites showed dynamic alterations of mutant alleles in C.sinensis stroma. The allele for the AT-biased genotypes at 067721-211 site showed higher peak height than its GC-biased counterpart in the premature C.sinensis stroma, but disappeared with C.sinensis maturation. Chromatograms displayed not only the transition mutation alleles, but also transversion mutants. Some of the transversion mutation alleles displayed higher peak heights than those for GC- and AT-biased alleles, but their peak heights and detection rates tended to be decreased with C.sinensis maturation. When distinguishing between the 2 AT-biases, AB067744 and AB067740 genotype alleles co-existed in the premature C.sinensis stroma. The allele peak height for AB067744 genotype was greatly decreased with C.sinensis maturation, while that for AB067740 genotype increased.

Conclusion: Co-existence of at least 5 transition and transversion mutant genotypes of O.sinensis and the dynamic changes in their expressions in C.sinensis stroma along with C.sinensis maturation may be of extreme importance in C.sinensis stroma germination and maturation, enabling C.sinensis to complete its life cycle.