Nucleotide Sequence and Characterization of the Large Mitochondrial rRNA Gene of Penicillium urticae, and Its Comparison with Those of Other Filamentous Fungi1

Abstract

The nucleotide sequence of a large rRNA gene and its flanking regions in cloned fragments of mitochondrial DNA from a patulin producer, Penicillium urticae NRRL2159A, was determined by dideoxy sequencing, and the 5' end and intron-exon border of the 1-rRNA gene were determined by primer extension analysis and RNA sequencing, respectively. In addition to the extensive sequence homology of the 3' end of the P. urticae mt 1-rRNA gene with those of Aspergillus nidulans and Neurospora crassa, the P. urticae gene had a 1,685 bp intron which separates a 3,307 bp 5' exon and a 583 bp 3' exon. In spite of being closely related Penicillium species, the size of the 5' exon of the P. urticae mt 1-rRNA is 472 bp larger than that of P. chrysogenum, whereas the sizes of the 3' exon and intron of P. urticae are very similar to those of P. chrysogenum (581 bp for the 3' exon and 1,678 bp for the intron). The intron of P. urticae contains a structure similar to the consensus one of the self splicing group IA intron and a large open reading frame suggested to be a gene for ribosomal protein S5. A sequence similar to the I-SceI recognition sequence was found at the exon-intron border. Extensive sequence homology was observed between P. urticae and P. chrysogenum, exceptions being in four regions in the 5' exon. These non-homologous regions were located in the hairpin and variable regions outside of the core structures. Comparison of the mt 1-rRNA sequences of several filamentous fungi revealed that the above four non-homologous regions are greatly expanded, and two other non-homologous regions appear at the 3' ends of the 5' exon and 3' exon.

In vivo expression of the nucleolar group I intron-encoded I-DirI homing endonuclease involves the removal of a spliceosomal intron

“…Host adaptation has been taken to the extreme in several mitochondrial introns which express structural genes that are important for host function. Examples include the ribosomal protein S5 which is encoded by LSU rDNA introns in Neurospora crassa and other fungi (Burke and RajBhandary, 1982; Cummings et al ., 1989; Yamamoto et al ., 1995), and two NADH dehydrogenase subunits which are expressed solely from introns in the ND5 gene of three sea anemone species (Beagley et al ., 1996). We propose that group I intron RNAs, by incorporating characteristic features of cellular transcripts, gain access to the normal mRNA maturation and transport pathways in the different compartments of their host cells.…”

Developments in Fungal Taxonomy

“…The first RFLP technique widely used in taxonomy compared patterns of mitochondrial DNA (mtDNA). However, some authors have sequenced the mtSSU rDNA instead (568,597). mtDNA is generally indicative of differences somewhat below the species level (268), but in groups where microspecies are currently distinguished, such as in the dermatophytes, the differences seem to correspond to teleomorph species (360).…”