The internal transcribed spacers and 5.8S rRNA gene show extensive diversity among isolates of the Cryptococcus neoformans species complex

Abstract

Sequences of the internal transcribed spacer (ITS) region including the 5.8S rRNA gene delineated seven genotypes within the three varieties of Cryptococcus neoformans via specific combinations of eight nucleotide differences located at positions 10, 11, 15, 19, 108 (ITS1), 221 (5.8S), 298 and 346 (ITS2). The ITS types correlated to polymerase chain reaction fingerprint/random amplification of polymorphic DNA (RAPD) molecular types: with ITS type 1 (ATACTAGC)=C. neoformans var. grubii, molecular types VNI+VNII and the serotype A allele of the AD hybrid, VNIIIA; ITS type 2 (ATATAGGC)=the serotype D allele of the AD hybrid, VNIIIB, and C. neoformans var. neoformans, VNIV; and ITS type 3 (GCGCTGGC) and ITS type 7 (ACGCTGGC)=VGI=RAPD type III, ITS type 4 (ACACTGAC)=VGII=RAPD type II, ITS type 5: (ACACTGGG)=VGIII=RAPD type I, ITS type 6 (ACACTGGC)=VGIV=RAPD type IV, all corresponding to C. neoformans var. gattii. Cloned sequences from serotype AD revealed that the hybrid serotype is diploid at the ITS1-5.8S-ITS2 locus carrying the ITS type 1 (ATACTAGC) and the ITS type 2 (ATATAGGC) alleles. ITS sequencing is a useful technique for genotyping the three C. neoformans varieties and for subtyping within C. neoformans var. gattii.