A trans-splicing model for the expression of the tripartite nad5 gene in wheat and maize mitochondria.

Abstract

The mitochondrial single-copy gene nad5 of wheat and maize consists of 5 exons located on three widely separated regions of the genome that are independently transcribed. The first region contains exons I and II separated by an atypical group II intron; in the second region is exon III (only 22 bp long), which is flanked upstream by a maturaserelated open reading frame (ORF) and exon e of the nadl gene, and downstream by a previously unidentified ORF (ORF143); in the third region are exons IV and V separated by a group II intron. In maize, this last domain is flanked upstream by the genes rps72, nadd, and tRNASer and downstream by a chloroplast tRNACys. RNA editing occurs in wheat exons IV and V as C -t o 4 changes. A detailed analysis of the transcription of the nad5 gene in wheat and maize reveals that the exons are assembled into a 2.4-kb mRNA after two cis-splicing (between exons I and II and exons IV and V) and two trans-splicing events. The trans-splicing process involves the sequences flanking exons II, 111, and IV that feature group II introns. A model is proposed for the assembly and maturation of the nad5 transcripts.

Trans‐splicing of organelle introns – a detour to continuous RNAs

“…(54) In D. papillatum, a member of diplonemids, which are a sister group of kinetoplastids, a fragmented cox1 gene encoded on two different chromosomes was found. Interestingly, the flanking regions do not exhibit any characteristics of organelle or nuclear introns nor contain trans IIB, tri, D4 Oenothera berteriana (49) nad5-i4 cis IIA, bi Arabidopsis thaliana, Brassica napus, Oenothera berteriana, Triticum aestivum, Vicia faba, Zea mays (49,105,111,112) This list contains examples that have thoroughly been analysed by cDNA and/or Northern or sequence analyses. A complete list of all organelle introns predicted to be trans-spliced is given in the supplemental material (Table S2).…”

The wheat mitochondrial genome contains an ORF showing sequence homology to the gene encoding the subunit 6 of the NADH-ubiquinone oxidoreductase

“…S1 mapping experiments were performed as described by Pereira de Souza et aI. [27]. The anchored PCR procedure in the 5' direction [ 18] was used to amplify the different batches of single-stranded cDNA.…”

“…Conserved sequences present in evolutionarily distant angiosperms may then reciprocally represent genes or part of genes [27]. That these sequences are functional genes must be confirmed by studying their expression.…”

Using 5′-PTMs to repair mutant β-globin transcripts

“…Trans-splicing is a naturally occurring phenomenon in some viruses, prokaryotes, lower eukaryotes, and possibly even in mammalian cells (Ziff and Evans 1978;Michel and Dujon 1983;Milhausen et al 1984;Blumenthal and Thomas 1988;Kohchi et al 1988;de Souza et al 1991;Finta and Zaphiropoulos 2002). The mechanism varies from the self-catalyzed reaction of the discontinuous group II intron to the spliceosome-driven splice leader approach used by nematodes and trypanosomes (Kohchi et al 1988;de Souza et al 1991).…”

“…The mechanism varies from the self-catalyzed reaction of the discontinuous group II intron to the spliceosome-driven splice leader approach used by nematodes and trypanosomes (Kohchi et al 1988;de Souza et al 1991). Trans-splicing can also be artificially derived by either modifying a natural splicing process, as in the group I ribozyme, or by manipulation of the cis-splicing machinery (Sullenger and Cech 1994;Puttaraju et al 1999).…”