Transition and transversion point mutations of Ophiocordyceps sinensis and their maturational alterations in stroma of Cordyceps sinensis

We previously reported the simultaneous detections of rDNA of Paecilomyces hepiali and Hirsutella sinensis (Hs) in Cordyceps sinensis (Cs), a precious Chinese herb, and the alteration of differential expression of Ophiocordyceps sinensis (Os) with changes of their phenotypes during Cs maturation ( J Fungal Research 5:214,2007; Am J BioMed Sci 2:217,2010). The biomass of Hs is much less than its mutant counterparts in Cs stroma. In this study we used MassARRAY SNP MALDI‐TOF MS genotyping to detect point mutations within Cs stroma rDNA. Eight SNP extension primers were designed based on alignment of the GC‐ & AT‐biased ITS sequences. When testing the genomic DNA isolated from premature Cs stroma, we found a GC‐ and 2 AT‐biased genotypes with multiple transition point mutations within Os rDNA and at least 2 transversion mutant genotypes of unknown sequences. Along with Cs maturation, alleles with transition nucleotide substitutes were less detected in genomic DNA isolated from maturing and mature Cs stroma, but those with transversion substitutes were consistently detected. The MS peak heights for the alleles in stroma rDNA were altered with Cs maturation. In conclusion, Cs stroma contains at least 5 transition and transversion mutation genotypes of Os that undergo maturational alterations. The Os mutations may be essential for Cs stroma germination and maturation, the key elements of Cs life cycle.