RNA editing in wheat mitochondria results in the conservation of protein sequences

Abstract

RNA editing is a process that results in the production of a messenger RNA with nucleotide sequences that differ from those of the template DNA, and provides another mechanism for modulating gene expression. The phenomenon was initially described in the mitochondria of protozoa. Here we report that RNA editing is also required for the correct expression of plant mitochondrial genes. It has previously been proposed that in plant mitochondria there is a departure from the universal genetic code, with CGG specifying tryptophan instead of arginine. This was because CGG codons are often found in plant mitochondrial genes at positions corresponding to those encoding conserved tryptophans in other organisms. We have now found, however, wheat mitochondrial gene sequences containing C residues that are edited to U residues in the corresponding mRNA sequences. In this way, CGG codons can be changed to UGG codons in the mRNA so that tryptophan may be encoded according to the universal genetic code. Furthermore, for each codon modification resulting from a C----U conversion that we studied, we found a corresponding change in the amino acid that was encoded. RNA editing in wheat mitochondria can thus maintain genetic information at the RNA level and as a result contribute to the conservation of mitochondrial protein sequences among plants.

RNA editing in wheat mitochondria proceeds by a deamination mechanism

“…The functional consequences of RNA editing in plant mitochondria are less understood [3][4][5]. Recent results suggest that mRNA editing plays an important role for the production of functional proteins [6].…”

Origins and evolution of ADAR‐mediated RNA editing

“…Although ADAR-mediated RNA editing is mechanistically very different from other types of editing in mitochondria and chloroplasts, they should have some parallel evolutionary rationale. In plants, it is suggested that RNA editing helps repair otherwise-deleterious genomic mutations (53)(54)(55)(56)(57). The ADAR-mediated RNA editing system is driven by genetic variation to maintain phylogenetic conservation, similar to plant mitochondrial RNA editing.…”

An RNA recognition motif-containing protein is required for plastid RNA editing in Arabidopsis and maize

“…Despite the discovery of plant RNA editing more than 20 y ago (7)(8)(9), only some of the components of the plant editosome are known. Cis-elements needed for recognition of C targets are usually found within 30 nt of the C to be edited (10)(11)(12)(13).…”