RNA editing in plants

Abstract

Higher plant mitochondrial RNAs undergo predetermined modifications which involve differences of splicing and trimming of the primary transcripts. These post‐transcriptional modifications are specific C‐to‐U changes occurring mostly in the coding regions of mRNAs without changing the reading frame. Editing of mRNAs can lead to the formation or initiation of stop codons. Plant mitochondrial proteins issued from edited mRNAs are more similar to non‐plant homologous proteins suggesting that this process is involved in the production of functional polypeptides. RNA editing in non‐coding regions are also observed and may represent a new mechanism for modulating gene expression. Three possible biochemical mechanisms can account for RNA editing in plant mitochondria: nucleotide replacement, base exchange and deamination. Although some evidence shows that RNA editing proceeds by a deamination mechanism, several questions remain to be solved: What are the signals recognised by the biochemical machinery for such a specific process? What are the reasons that make an additional process acquired by land plant mitochondria for faithful gene expression?

Transgenic male-sterile plant induced by an unedited atp9 gene is restored to fertility by inhibiting its expression with antisense RNA.

“…RNA editing in plant mitochondria involves the substitution of some C residues present in the initial transcript for U residues. The mitochondrial protein sequences predicted from edited transcripts are more similar to homologous proteins from other organisms than are proteins predicted from unedited mRNAs (16,17). This observation suggests that the editing process assures the synthesis of functional mitochondrial proteins.…”

RNA editing in wheat mitochondria proceeds by a deamination mechanism

“…Plasmid pG300 containing the complete coding region of subunit 9 of mitochondrial ATP synthase gene (atp9), pHNED3'-S carrying an insert of 66 nucleotides bearing codons 61 75 ofatp9 [9] and pNADC2 containing the sequence from -8 to 17 ofnad3 [12] were used for in vitro synthesis of unedited RNA substrates. In vitro transcription was catalyzed by T7 RNA polymerase.…”

“…Contrary to the mammalian system where RNA editing seems tissue-specific and is restricted to a very limited number of transcripts, RNA editing in plant mitochondria is produced in most plant tissues and involves almost all the protein coding transcripts and some structural RNAs ( [9] and references therein). RNA editing in plant organelles is characterized by C-to-U conversion of some residues in the transcript.…”

RNA editing in plant mitochondria, cytoplasmic male sterility and plant breeding

“…After that, RNA editing has been found in mitochondria and chloroplasts from land plants, in the mitochondria of some fungi, in the nuclear-cytoplasmic compartments from animal cells and in the genomes of some viruses. The RNA editing process involves in some cases the modification of residues in RNA or, in other cases, the insertion and/or deletion of nucleotides in messenger RNA (for some reviews see Adler and Hadjuk, 1994;Araya et al, 1994;Schuster and Brennicke, 1994;Scott, 1995;Smith et al, 1997;Stuart et al, 1997). The consequences of the RNA editing process are either the modification of the coded information for some amino acids or the generation of new initiation and/or termination codons.…”

“…Different types of RNA editing. More details which are not described in the text can be found in the reviews by (Araya et al, 1994;Schuster and Brennicke, 1994;Scott, 1995;Hanson et al, 1996;Smith et al, 1997;Stuart et al, 1997). This table has been adapted from Smith et al, 1997. Two different types of RNA editing have been described.…”