GROUP I INTRONS FOUND IN NUCLEAR SMALL SUBUNIT RIBOSOMAL RNA GENES OF THE BALLISTOCONIDIOGENOUS ANAMORPHIC YEAST BENSINGTONIA CILIATA AND BENSINGTONIA YAMATOANA

Abstract

Four group I introns were found in the nuclear small subunit ribosomal RNA genes (SSU rDNA) of the ballistoconidiogenous anamorphic yeast genus Bensingtonia. Two of them were found in B. ciliata, type species of the genus, with the length of 335nt and 341nt. The remaining two were
found in B. yamatoana with lengths of 454nt and 457nt, respectively. The four introns were located at two different sites within the SSU rDNA. The first insertion site was the same position as group I introns found in the SSU rDNA of Dunaliella parva-5′, Dunaliella sauna, Protomyces inouyei-5′ and Ustilago maydis. The second insertion site was shared among group I introns found in the SSU rDNA of Chlorella ellipsoidea, Hildenbrandia rubra, Pneumocystis carinii and Protomyces inouyei-3′. The putative secondary structures of the introns resembled those of subgroup IC1. Principal coordinate analysis of core regions of 15 group I introns found in SSU rDNA of eukaryotes showed that the sequence of B. ciliata- 5′ intron resembled that of the B. yamatoana-5′ intron, and the sequence of the B. yamatoana-3′ intron resembled that of the Protomyces inouyei-5′ intron. Bensingtonia ciliata-3′ intron had relatively different sequences compared to other group I introns examined. Group I introns in the nuclear SSU rDNA of red and green algae, ascomycetes and basidiomycetes, examined in this study, were scattered on the principal coordinate analysis.