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[Organization of ribosomal DNA from the phytoflagellates Astasia longa and Euglena gracilis: comparison of the structure of 19S and 28S rRNA genes].

Restriction maps of Astasia longa and Euglena gracilis var. bacillaris were built and localization of 5.8S, 19S and 28S rRNA genes was established on them by blot-hybridization method. In the A. longa and E. gracilis plasmid rDNA three intergeneous regions were found, two of which were intergeneous transcribed spacers flanking 5.8S RNA gene, and the third region seems to be an untranscribed spacer. Localization of 9 primers from E. gracilis was established on A. longa 19S rRNA gene by PCR; it was similar to E. gracilis. Using amplified A. longa 19S rRNA gene (2300 bp) we have determined the sequence of its 3'-region, which showed 87% homology with the same region of E. gracilis. Using plasmid pA1 S3-H1 containing S3-H1 fragment of A. longa rDNA the sequence of 28S rRNA gene 3'-region was determined. This sequence includes regions homologous to corresponding regions of E. gracilis Z: 6 nucleotides of 12/13 internal spacer, complete 13/14 internal spacer (86 bp), genes for 13th and 14th 28S rRNA components (56 and 86 bp) with approximately 90% of homology with E. gracilis Z, and fragment of untranscribed spacer (136 bp) with approximately 70% homology. It was shown that 28S rRNA genes of A. longa and E. gracilis have similar structure. Our data allow to conclude that these phytoflagellats are closely related.

Animals↗
PubMed2006

Tobacco plastid ribosomal protein S18 is essential for cell survival.

Plastid genomes contain a conserved set of genes most of which are involved in either photosynthesis or gene expression. Among the ribosomal protein genes present in higher plant plastid genomes, rps18 is special in that it is absent from the plastid genomes of several non-green unicellular organisms, including Euglena longa and Toxoplasma gondii. Here we have tested whether the ribosomal protein S18 is required for translation by deleting the rps18 gene from the tobacco plastid genome. We report that, while deletion of the rps18 gene was readily obtained, no homoplasmic Deltarps18 plants or leaf sectors could be isolated. Instead, segregation into homoplasmy led to severe defects in leaf development suggesting that the knockout of rps18 is lethal and the S18 protein is required for cell survival. Our data demonstrate that S18 is indispensable for plastid ribosome function in tobacco and support an essential role for plastid translation in plant development. Moreover, we demonstrate the occurrence of flip-flop recombination on short inverted repeat sequences which generates different isoforms of the transformed plastid genome that differ in the orientation a 70 kb segment in the large single-copy region. However, infrequent occurrence of flip-flop recombination and random segregation of plastid genomes result in the predominant presence of only one of the isoforms in many tissue samples. Implications for the interpretation of chloroplast transformation experiments and vector design are discussed.

Cell Survival↗
PubMed1990

Genes for ribosomal proteins are retained on the 73 kb DNA from Astasia longa that resembles Euglena chloroplast DNA.

The nucleotide sequence of a 6.7 kb segment of the circular 73 kb DNA from 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, almost exclusively, genes for a plastid-type translational (and presumably transcriptional) apparatus.

Amino Acid Sequence↗
PubMed2001

Physiological characterization of gravitaxis in Euglena gracilis and Astasia longa studied on sounding rocket flights.

Euglena gracilis is a photosynthetic, unicellular flagellate found in eutrophic freshwater habitats. The organisms control their vertical position in the water column using gravi- and phototaxis. Recent experiments demonstrated that negative gravitaxis cannot be explained by passive buoyancy but by an active physiological mechanism. During space experiments, the threshold of gravitaxis was determined to be between 0.08 and 0.12 x g. A strong correlation between the applied acceleration and the intracellular cAMP and Ca2+ was observed. The results support the hypothesis, that the cell body of Euglena, which is denser than the surrounding medium exerts a pressure onto the lower membrane and activates mechanosensitive Ca2+ channels. Changes in the membrane potential and the cAMP concentration are most likely subsequent elements in a signal transduction chain, which results in reorientation strokes of the flagellum.

Animals↗
PubMed2003

Gravitactic signal transduction elements in Astasia longa investigated during parabolic flights.

Euglena gracilis and its close relative Astasia longa show a pronounced negative gravitactic behavior. Many experiments revealed that gravitaxis is most likely mediated by an active physiological mechanism. The goal of the present study was to examine elements in the sensory transduction by means of inhibitors of gravitaxis and the intracellular calcium concentration during short microgravity periods. During the course of six parabolic flights (ESA 31th parabolic flight campaign and DLR 6th parabolic flight campaign) the effects of trifluoperazine (calmodulin inhibitor), caffeine (phosphodiesterase inhibitor) and gadolinium (blocks mechano-sensitive ion channels) was investigated. Due to the extreme parabolic flight maneuvers of the aircraft alternating phases of 1.8 x g(n) (about 20 s) and microgravity (about 22 s) were achieved (g(n): acceleration of Earth's gravity field). The duration of the microgravity periods was sufficient to detect a loss of cell orientation in the samples. In the presence of gadolinium impaired gravitaxis was found during acceleration, while caffeine-treated cells showed, compared to the controls, a very precise gravitaxis and faster reorientation in the 1.8 x g(n) period following microgravity. A transient increase of the intracellular calcium upon increased acceleration was detected also in inhibitor-treated samples. Additionally, it was found that the cells showed a higher calcium signal when they deviated from the vertical swimming direction. In the presence of trifluoperazine a slightly higher general calcium signal was detected compared to untreated controls, while gadolinium was found to decrease the intracellular calcium concentration. In the presence of caffeine no clear changes of intracellular calcium were detected compared to the control.

Acceleration↗