Editing site recognition in plant mitochondria: The importance of 5'-flanking sequences

Mark A. Williams, Brenda M. Kutcher, R. Michael Mulligan

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


Cytidine to uridine (C-to-U) editing occurs in plant mitochondria with very high specificity such that only specific cytidines are converted to uridines. The mechanisms for editing site selection in plant mitochondria are unknown. In order to examine the determinants of editing site recognition, repeated mitochondrial DNA sequences that include edited nucleotides have been evaluated as editing substrates. During evolution the maize mitochondrial ribosomal protein subunit 12 (rps12) gene recombined with intron 1 of the ribosomal protein subunit 3 (rps3) gene and a region of the S1-like sequence of the 2.3 kb plasmid. These recombinations created a second copy of an internal portion of the rps12 gene, known as rps12b, which includes the first four editing sites of rps12 transcripts. The duplicated sequence extends seven nucleotides upstream of editing site 1 and six nucleotides downstream from editing site 4. The sequences of rps12 and rps12b are identical between these sites except for a single change at -5 from editing site 1. These modifications did not affect C-to-U conversion at editing sites 2, 3, or 4 in rps12b; however, no editing was detected at editing site 1 in rps12b cDNAs. Thus, the 5' recombination abolished editing at site 1, while the 3' recombination modified the downstream RNA sequence, but did not effect editing at site IV. Secondary structure prediction suggests that changes in editing site recognition do not correlate with differences in secondary structures, and that primary RNA sequence may be responsible for editing site specification.

Original languageEnglish
Pages (from-to)229-237
Number of pages9
JournalPlant Molecular Biology
Issue number2
StatePublished - Jan 1998

Bibliographical note

Funding Information:
The authors wish to thank Dr William Rapp of St. Louis University, Saint Louis, MO for sharing the genomic sequence of the rps12b region. This research was supported by USDA grant 94-37301-0498 and by grant RG-437-94-M from the International Human Frontiers Science Program to RMM. Support for MAW was provided by NIH training grant PHS/NIH 5T32GM07311. Maize seed was a gift from Pioneer Hi-bred Seed Company (Johnston, IA).


  • C-to-U editing
  • Editing site recognition
  • RNA editing
  • Ribosomal protein subunit 12

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Genetics
  • Plant Science


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