Organization and expression of organellar genomes

Protist mitochondrial genomes show a very wide range of gene content, ranging from three genes for respiratory chain components in Apicomplexa and dinoflagellates to nearly 100 genes in Reclinomonas americana. In many organisms the rRNA genes are fragmented, although still functional. Some protist m...

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Bibliographic Details
Published in:Philosophical transactions of the Royal Society of London. Series B. Biological sciences 2010-03, Vol.365 (1541), p.785-797
Main Authors: Barbrook, Adrian C., Howe, Christopher J., Kurniawan, Davy P., Tarr, Sarah J.
Format: Article
Language:English
Subjects:
Algae
Apicoplast
Biological Evolution
Chloroplasts
Gene Expression
Genes
Genome
Genome, Chloroplast
Genome, Mitochondrial
Genomes
Introns
Kinetoplast
Maxi-Circle
Messenger RNA
Mini-Circle
Mitochondria
Mitochondrial DNA
Nucleomorph
Organelles - genetics
Plastid
Reviews
RNA
RNA - genetics
Symbiosis - genetics
Transfer RNA
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Summary:Protist mitochondrial genomes show a very wide range of gene content, ranging from three genes for respiratory chain components in Apicomplexa and dinoflagellates to nearly 100 genes in Reclinomonas americana. In many organisms the rRNA genes are fragmented, although still functional. Some protist mitochondria encode a full set of tRNAs, while others rely on imported molecules. There is similarly a wide variation in mitochondrial genome organization, even among closely related groups. Mitochondrial gene expression and control are generally poorly characterized. Transcription probably relies on a ‘viral-type’ RNA polymerase, although a ‘bacterial-type’ enzyme may be involved in some cases. Transcripts are heavily edited in many lineages. The chloroplast genome generally shows less variation in gene content and organization, although greatly reduced genomes are found in dinoflagellate algae and non-photosynthetic organisms. Genes in the former are located on small plasmids in contrast to the larger molecules found elsewhere. Control of gene expression in chloroplasts involves transcriptional and post-transcriptional regulation. Redox poise and the ATP/ADP ratio are likely to be important determinants. Some protists have an additional extranuclear genome, the nucleomorph, which is a remnant nucleus. Nucleomorphs of two separate lineages have a number of features in common.
ISSN:0962-8436
1471-2970
DOI:10.1098/rstb.2009.0250