ReviewThe transcription machineries of plant mitochondria and chloroplasts: Composition, function, and regulation
Introduction
Mitochondria and plastids possess their own genomes and transcription machineries. Although both organelles preserve features of eubacterial genomes, they have acquired, during their evolution, specialized components for gene expression, which are encoded in the nucleus. During the co-evolution of plastids (cyanobacterial endosymbiont) and the eukaryotic host cell massive losses of genes from the chondrome (mitochondrial genome) and plastome (plastid genome) have occurred (Martin et al., 2002, Dyall et al., 2004, Gray, 2004, Gray, 2010, Knoop, 2004, Richly and Leister, 2004, Brandvain and Wade, 2009). However, the cells did not lose all of those genes, since thousands of them have been transferred to the nucleus, still a relatively frequent and ongoing process (Brennicke et al., 1993, Martin and Herrmann, 1998, Palmer et al., 2000, Herrmann et al., 2003, Martin, 2003, Adams and Daley, 2004, Timmis et al., 2004, Leister, 2005, Stegemann and Bock, 2006). A considerable number of proteins encoded by those genes were rerouted back into the plastids/mitochondria by acquiring plastid and/or mitochondrial targeting sequences. In a similar way, many nuclear-encoded proteins of non-organellar origin also became part of the organellar proteome (eukaryotization; Sato, 2001, Hengeveld and Fedonkin, 2004). This eukaryotization is also reflected by the transcriptional machineries of mitochondria and plastids in higher plants. Considering the small sizes of the chondromes and plastomes of higher plants compared to the genomes of their bacterial ancestors, the transcriptional machineries of mitochondria and even more of plastids are surprisingly complex. Here we describe the different components of the transcriptional machinery in mitochondria and plastids and their roles in transcription and its regulation.
Section snippets
Mitochondrial RNA polymerases are phage-type enzymes
Mitochondrial transcription is performed by nuclear-encoded phage-type RNA polymerase(s) (RNAP(s); reviewed in Tracy and Stern, 1995, Hess and Börner, 1999, Weihe, 2004, Liere and Börner, 2011). The protist Reclinomonas americana is the only known organism which has retained the ancestral bacterial RNAP genes in its chondrome (Lang et al., 1997). While most eukaryotes including also algae and the lycophyte Selaginella moellendorffii (Yin et al., 2009) possess only one nuclear gene for a (in
PEP: the plastid-encoded plastid RNA polymerase
The plastomes of algae and higher plants possess rpoA, rpoB, rpoC1, and rpoC2 genes for core subunits of a cyanobacterial-type RNA polymerase, which is commonly abbreviated as PEP (plastid-encoded plastid RNA polymerase; Lysenko and Kuznetsov, 2005, Shiina et al., 2005, Liere and Börner, 2007a, Liere and Börner, 2007b). PEP ß- and ß′-subunits can functionally substitute homologous subunits of the E. coli RNA polymerase (Severinov et al., 1996). Furthermore, PEP exhibits sensitivity to
Acknowledgements
The work of the authors is supported by Deutsche Forschungsgemeinschaft (SFB 429). We thank Kristina Kühn for providing initial artwork.
References (343)
- et al.
Mitochondrial transcription and its regulation in mammalian cells
Trends Biochem Sci
(2007) - et al.
Participation of nuclear genes in chloroplast gene expression
Biochimie
(2000) - et al.
Transcription initiation sites in mitochondria of Oenothera berteriana
J Biol Chem
(1993) - et al.
A novel pea mitochondrial in vitro transcription system recognizes homologous and heterologous mRNA and tRNA promoters
J Biol Chem
(1995) - et al.
The mitochondrial genome on its way to the nucleus: different stages of gene transfer in higher plants
FEBS Lett
(1993) - et al.
Transcription and processing of the gene for spinach chloroplast threonine tRNA in a homologous in vitro system
Biochem Biophys Res Commun
(1997) - et al.
Continuous primary sequence requirements in the 18-nucleotide promoter of dicot plant mitochondria
J Biol Chem
(1999) - et al.
Complete nucleotide sequence of bacteriophage T7 DNA and the locations of T7 genetic elements
J Mol Biol
(1983) - et al.
Characterization of plastid DNA transcription in ribosome deficient plastids of heat-bleached barley leaves
J Plant Physiol
(1993) - et al.
Compilation and analysis of plant mitochondrial promoter sequences: an illustration of a divergent evolution between monocot and dicot mitochondria
Biochem Biophys Res Commun
(1999)