Diversity of the ribosomal structures in the Euglena gracilis chloroplast genome: description of a mutant with two ribosomal operons and possible mechanism for its production (original) (raw)
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Processing of chloroplast ribosomal RNA transcripts in Euglena gracilis bacillaris
Current Genetics, 1989
The ribosomal RNA operons (rrn operons) of Euglena gracilis chloroplasts contain genes for (in order) 16S rRNA, tRNA ne, tRNA Ala, 23S rRNA and 5S rRNA. Major sites of cleavage of the primary rrn transcript were identified by Northern blot hybridization and S 1-mapping. The presumptive termini of all of the mature products have now been identified. During initial processing in the chloroplast, the primary transcript is cleaved between the two tRNAs and between the 23S and 5S rRNAs so as to separate the sequences found in the different mature rRNAs. Subsequently the tRNAs are separated from the rRNAs, further trimming provides the remaining proper ends, and the 3'ends of the tRNAs are added.
Complete sequence of Euglena gracilis chloroplast DNA
Nucleic Acids Research, 1993
We report the complete DNA sequence of the Euglena gracilis, Pringsheim strain Z chloroplast genome. This circular DNA is 143,170 bp, counting only one copy of a 54 bp tandem repeat sequence that is present in variable copy number within a single culture. The overall organization of the genome involves a tandem array of three complete and one partial ribosomal RNA operons, and a large single copy region. There are genes for the 16S, 5S, and 23S rRNAs of the 70S chloroplast ribosomes, 27 different tRNA species, 21 ribosomal proteins plus the gene for elongation factor EF-Tu, three RNA polymerase subunits, and 27 known photosynthesis-related polypeptides. Several putative genes of unknown function have also been identified, including five within large introns, and five with amino acid sequence similarity to genes in other organisms. This genome contains at least 149 introns. There are 72 individual group 1I introns, 46 individual group Ill introns, 10 group 11 introns and 18 group Ill introns that are components of twintrons (introns-within-introns), and three additional introns suspected to be twintrons composed of multiple group 11 and/or group Ill introns, but not yet characterized. At least 54,804 bp, or 38.3% of the total DNA content is represented by introns.
Nucleic Acids Research, 1984
We characterize a DNA segment of the Euglena gracills chloroplast DNA fragment Eco-N by nucleotlde sequencing and SI nuclease analysis. We show that this region, which is upstream of the previously sequenced tuf A gene, contains the genes for the ribosomal proteins S12 and S7. The gene arrangment is 5'-rps 12-80 bp spacer-rps 7-174 bp 3pacer-tuf A, somewhat similar to the str operon of E. coll. The chloroplast S12 and S7 proteins contain 124 and 155 aminoacids, respectively, and are to 68% and 38% homologous with the corresponding E. coll proteins. The region is transcribed into a distronic mRNA of about 1.1 to 1.2 kb. The rps 12 and rps 7 genes, contrary to the tuf A gene, are not split.
Current Genetics, 1981
Chloroplast DNAs from six different laboratory collections of Euglena gracilis "strain Z" and var. bacillaris were analyzed with restriction endonucleases EcoRI and Barn HI. The most variable portion of the organelle genome is the region containing the ribosomal cistrons. Intraspecific differences occur in both ribosomal DNA cistron number (one or three) and structural organization among those strains designated as "strain Z" and bacillaris. One culture previously designated as "Z" is most likely bacillaris.
Nucleic Acids Research, 1984
We characterize a DNA segment of the Euglena gracills chloroplast DNA fragment Eco-N by nucleotlde sequencing and SI nuclease analysis. We show that this region, which is upstream of the previously sequenced tuf A gene, contains the genes for the ribosomal proteins S12 and S7. The gene arrangment is 5'-rps 12-80 bp spacer-rps 7-174 bp 3pacer-tuf A, somewhat similar to the str operon of E. coll. The chloroplast S12 and S7 proteins contain 124 and 155 aminoacids, respectively, and are to 68% and 38% homologous with the corresponding E. coll proteins. The region is transcribed into a distronic mRNA of about 1.1 to 1.2 kb. The rps 12 and rps 7 genes, contrary to the tuf A gene, are not split.
Isolation of Mutants of Euglena gracilis With Impaired Photosynthesis
PLANT PHYSIOLOGY, 1968
A bstract. Four mutant strains of Euglena gracilis have been isolated after treatment of wild type cells with ultraviolet light or the chemtical mutagen nitrosoguanidine. None of the mutants is capable of autotrophic growth or photosynthetic carbon dioxide fixation. The mutant strains contain normal amounts of the enzymes of the reductive pentose phosphate cycle and are qualitatively similar to the wild type in pigment composition, but are unable to carry out the Hill reaction (light induced reduction of 2,6-dichlorophenol indophenol). Isolated mutant plastids cannot photoreduce NADP with water as the electron donor but can carry out this reaction when the electron donating system is ascorbate and 2,6-dichlorophenol indophenol. Whole cells of the mutants show the light induced oxidation of cytochrome f by light reaction I but are unable to bring about cytochrome t reduction by light reaction II. The mutants appear to be blocked at or near light reaction II in the photosynthetic electron transport chain. The mutants may represent alterations of the chloroplast genome since the mutation isolation was carried out under conditions where chloroplast viability was severely impaired. but cell viability was unaffected.
Current genetics, 1990
Astasia longa has been determined. We identified genes for a tRNA-Ile (CAU), a tRNA-Phe (GAA), a tRNA-Cys (GCA) and the ribosomal proteins CS8, CL36, CS14 and CS2, that are normally encoded by plastid genomes. In addition, a gene for the chloroplast ribosomal protein CL5 was found that is not encoded by the plastome in either higher plants or a liverwort, but has recently been identified in Euglena chloroplast DNA. Transcripts of these protein genes, and of an unidentified open reading frame (ORF50), were detected. These results support our previous suggestion that the 73 kb DNA from Astasia is a truncated form of plastid DNA. The 73 kb DNA resembles the chloroplast DNA of Euglena gracilis but contains, ahnost exclusively, genes for a plastid-type translational (and presumably transcriptional) apparatus.