Cyanelle DNA from Cyanophora paradoxa (original) (raw)
1985, Molecular and General …
Cyanelles which have been found in few eukaryotic organisms are photosynthetically active organelles which strikingly resemble cyanobacteria. The complexity of the cyanelle genome in Cyanophora paradoxa (127 Kbp) is too low to consider them as independent organisms in a symbiotic relationship. In order to correlate cyanelle genome and gene structure with those of plastid chromosomes of other plants, a circular map of the cyanelle DNA from Cyanophora paradoxa (strain LB555 UTEX) has been constructed using the restriction endonucleases Sa/I (generating 6 DNA fragments), BamHI (6), Sinai (5), XhoI (9), and BgllI (19). Besides the rRNA genes (16S, 23S, 5S), genes for 14 proteins have been located on this circular map. Among those are components of several multienzyme complexes involved in photosynthetic electron transport, as well as the large subunit of ribulose-l,5-bisphosphate carboxylase and two ribosomal proteins. All the probes used, were derived from a collection of spinach chloroplast DNA clones. Hybridization experiments showed signals to DNA fragments primarily from the large single-copy region of cyanelle DNA. The arrangement of genes on cyanelle DNA is different from that on spinach chloroplast DNA. However, genes which have been shown to be cotranscribed in spinach chloroplasts are also clustered on cyanelle DNA.
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J Mol Evol, 1986
The 5S ribosomal RNAs from the cell cytoplasm and cyanelle (photosynthetic organelle) of Cyanophora paradoxa have been isolated and sequenced. The cellular and cyanelle 5S rRNAs were 119 and 118 nucleotides in length, respectively. Both RNAs exhibited typical 5S secondary structure, but the primary sequence of the cellular species was clearly eukaryotic in nature, while that of the organellar species was prokaryotelike. The primary sequence of the cyanellar 5S rRNA was most homologous to cyanobacterial 5S sequences, yet possessed secondary-structural features characteristic of higher-plant chloroplast 5S rRNAs. Both sequence comparison and structural analysis indicated an evolutionary position for cyanelle 5S rRNA intermediate between blue-green alga and chloroplast 5S rRNAs.
Mapping of rRNA genes in an inverted repeat in Nicotiana tabacum chloroplast DNA
Nucleic Acids Research, 1980
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Journal of Eukaryotic Microbiology, 2009
The glaucocystophyte Cyanophora paradoxa is an obligatorily photoautotrophic biflagellated protist containing cyanelles, peculiar plastids surrounded by a peptidoglycan layer between their inner and outer envelope membranes. Although the 136-kb cyanelle genome surpasses higher plant chloroplast genomes in coding capacity by about 50 protein genes, these primitive plastids still have to import 42,000 polypeptides across their unique organelle wall. One such protein is transketolase, an essential enzyme of the Calvin cycle. We report the sequence of the pre-transketolase cDNA from C. paradoxa and in vitro import experiments of precursor polypeptides into cyanelles and into pea chloroplasts. The transit sequence clearly indicates the localization of the gene product to cyanelles and is more similar to the transit sequences of the plant homologues than to transit sequences of other cyanelle precursor polypeptides with the exception of a cyanelle consensus sequence at the N-terminus. The mature sequence reveals conservation of the thiamine pyrophosphate binding site. A neighbor-net planar graph suggests that Cyanophora, higher plants, and the photosynthetic protist Euglena gracilis acquired their nuclear-encoded transketolase genes via endosymbiotic gene transfer from the cyanobacterial ancestor of plastids; in the case of Euglena probably entailing two transfers, once from the plastid in the green algal lineage and once again in the secondary endosymbiosis underlying the origin of Euglena's plastids. By contrast, transketolase genes in some eukaryotes with secondary plastids of red algal origin, such as Thalassiosira pseudonana, have retained the pre-existing transketolase gene germane to their secondary host.
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