Nucleic Acids Research, 1989, Vol. 17, No. 22 9087-9099
© 1989
MOLECULAR BIOLOGY |
A group II intron in the Neurospora mitochondrial col gene: nucleotide sequence and implications for splicing and molecular evolution
Department of Botany and Centre for Plant Biotechnology, University of Toronto Toronto, Ontario M5S 3B2, Canada
*To whom correspondence should be addressed
Received August 14, 1989. Revised October 18, 1989. Accepted October 18, 1989.
The temperature-sensitive Neurospora nuclear mutant cyt18-1 is deficient in splicing many Group I mitochondrial introns when grown at its non-permissive temperature; however, splicing of intron 1 in the col gene of the Adiopodoume (formerly called North Africa) strain is unaffected (R.A. Collins and A.M. Lambowitz, J. Mol. Biol. 184: 413–428, 1985). Here we show that col intron 1 is a typical Group II intron, the only one identified to date in Neurospora. The differential effect of the cyt18-1 mutation suggests that splicing of certain introns could be regulated independently of others by nuclear-encoded proteins. The intron contains a long open reading frame (ORF) resembling that of the Neurospora Mauriceville mitochondrial plasmid. The intron and plasmid ORFs share unusual features of codon usage that suggest both evolved outside of the Neurospora mitochondrial genetic system.
+Present address: Department of Genetics, Hospital for Sick Children, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada