Occurrence and characteristics of group 1 introns found at three different positions within the 28S ribosomal RNA gene of the dematiaceous <it>Phialophora verrucosa</it>: phylogenetic and secondary structural implications

• Main Authors: Hashizume Toko, Takizawa Kayoko, Kamei Katsuhiko
• Format: Article
• Language: English
• Published: BMC 2011-05-01
• Series: BMC Microbiology
• Online Access: http://www.biomedcentral.com/1471-2180/11/94

<p>Abstract</p> <p>Background</p> <p>Group 1 introns (ribozymes) are among the most ancient and have the broadest phylogenetic distribution among the known self-splicing ribozymes. Fungi are known to be rich in rDNA group 1 introns. In the present study, five sequences of the 28S ribosomal RNA gene (rDNA) regions of pathogenic dematiaceous <it>Phialophora verrucosa </it>were analyzed using PCR by site-specific primers and were found to have three insertions, termed intron-F, G and H, at three positions of the gene. We investigated the distribution of group 1 introns in this fungus by surveying 34 strains of <it>P. verrucosa </it>and seven strains of <it>Phialophora americana </it>as the allied species.</p> <p>Results</p> <p>Intron-F's (inserted at L798 position) were found in 88% of <it>P. verrucosa </it>strains, while intron-G's (inserted at L1921) at 12% and intron-H's (inserted at L2563) at 18%. There was some correlation between intron distribution and geographic location. In addition, we confirmed that the three kinds of introns are group 1 introns from results of BLAST search, alignment analysis and Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR). Prediction of secondary structures and phylogenetic analysis of intron sequences identified introns-F and G as belonging to subgroup IC1. In addition, intron-H was identified as IE.</p> <p>Conclusion</p> <p>The three intron insertions and their insertion position in the 28S rDNA allowed the characterization of the clinical and environmental isolates of <it>P. verrucosa </it>and <it>P. americana </it>into five genotypes. All subgroups of introns-F and G and intron-H were characterized and observed for the first time in both species.</p>