Cellular content of chloroplast DNA and chloroplast ribosomal RNA genes in Euglena gracilis during chloroplast development

Chelm, Barry K.; Hoben, Patricia; Hallick, Richard B.

doi:10.1021/bi00623a033

Cited by 36 publications

(13 citation statements)

References 19 publications

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“…It can be seen from the analyses listed in Table 1 that the chemical complexity of the high-abundance Pst-A RNA transcripts (14-15 kb, depending on the stage of development) is in agreement with its assignment as rRNA. The abundance of these transcripts is also in agreement with the abundances previously determined by using a hybridization probe specific for chloroplast rRNA (9). It may therefore be concluded that the cellular RNA that hybridizes with Pst-A at low Rot values is chloroplast rRNA.…”

Section: Resultssupporting

confidence: 88%

Transcription program of the chloroplast genome of Euglena gracilis during chloroplast development

Chelm

Hallick

Gray

1979

Proc. Natl. Acad. Sci. U.S.A.

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RNA transcription in Euglena gracifis chloroplasts has been characterized by hybridization of RNA from cells at different stages of chloroplast development to 3H-labeled chloroplast DNA restriction endonuclease fragments. Chloroplast DNA was digested into five fragments of 53,000, 35,000, 25,000, 10,000, and 6900 base pairs with Pst I. The 53,000-base-pair DNA When Euglena is grown in the dark on an oxidizable carbon source the cells lose the photosynthetic pigments and lamellae of the chloroplasts. The chloroplasts also lose the components of photosynthetic electron transport and the ability to fix CO2. In the dark, chloroplasts are replaced by proplastids, an organelle containing chloroplast DNA surrounded by a double membrane (1, 2). When dark-adapted cells are shifted to the light, chloroplast development begins whether the cells are dividing or not. Development is a temporal process, marked by the acquisition of properties of mature chloroplasts at specific intervals after the onset of light-induced development. The process is complete after 72 hr. with each cell having a full complement of mature chloroplasts (1, 2).We have been studying the changes in RNA transcription in the chloroplasts during light-induced development. Euglena chloroplast DNA, which has a genome size of 130,000-140,000 base pairs (130-140 kbp) (3, 4), is extensively transcribed at all developmental stages (5, 6). However, the extent of transcription varies significantly with both the developmental stage and the culture conditions. In exponentially growing cells on a phototrophic medium, there is an initial decrease in the fraction of the genome transcribed during the first 4 hr of growth in the light. Subsequently an induction of RNA synthesis occurs, reaching a maximum value 72 hr after the onset of development. At this time 23-26% of the DNA is transcribed, yielding RNA of 60-65 kilobase (kb) complexity (5, 7).Since these results were reported, a detailed restriction endonuclease map of the Euglena chloroplast genome has been published (4,8). With the map as reference, it has been possible to locate regions of the genome containing developmentally regulated transcription units. Specific restriction fragments from chloroplast DNA were purified, radioactively labeled to high specific activity in vitro, and utilized as hybridization probes for specific regions of the chloroplast genome. The restriction fragments used in this study were of known position on the chloroplast genome, and in aggregate represent the entire DNA sequence content. By using these hybridization probes, transcription was quantitatively studied at three stages: before induction of chloroplast development in dark-adapted cells, early during chloroplast development, and at a late stage of chloroplast development. From the results it can be concluded that the chloroplast genome contains several different types of transcription units, which can be characterized by their pattern of regulation. METHODSPreparation of RNA. The preparation of dark-adapted cultures ...

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Section: Resultssupporting

confidence: 88%

Transcription program of the chloroplast genome of Euglena gracilis during chloroplast development

Chelm

Hallick

Gray

1979

Proc. Natl. Acad. Sci. U.S.A.

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“…The latter case might be detected because of the fewer copies of plastid DNA molecules in the dark in comparison to the light conditions. It was shown that after transition from dark to light, the number of plastid DNA molecules and plastid rRNA genes in E. gracilis increases from 200 to 1400-2900 and from 1900 to 5200 per cell, respectively [10,37].…”

Section: Discussionmentioning

confidence: 99%

A small portion of plastid transcripts is polyadenylated in the flagellate Euglena gracilis

et al. 2014

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Edited by Ulf-Ingo FlüggeKeywords: Plastid EST Euglenozoa Polyadenylation Quantitative PCR Trans-splicing a b s t r a c t Euglena gracilis possesses secondary plastids of green algal origin. In this study, E. gracilis expressed sequence tags (ESTs) derived from polyA-selected mRNA were searched and several ESTs corresponding to plastid genes were found. PCR experiments failed to detect SL sequence at the 5 0 -end of any of these transcripts, suggesting plastid origin of these polyadenylated molecules. Quantitative PCR experiments confirmed that polyadenylation of transcripts occurs in the Euglena plastids. Such transcripts have been previously observed in primary plastids of plants and algae as low-abundance intermediates of transcript degradation. Our results suggest that a similar mechanism exists in secondary plastids. Ó 2014 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved. IntroductionEuglena gracilis is a fresh-water photosynthetic flagellate belonging to the order Euglenida and to the protist phylum Euglenozoa [1,2]. This phylum includes also the orders Kinetoplastida, Diplonemida and Symbiontida [3,4], which comprise exclusively heterotrophic species. Most euglenid species are free-living heterotrophic flagellates, but some of them possess secondary plastids that arose via secondary endosymbiosis of a green alga [5]. Phylogenetic analysis of plastid genome sequences revealed that euglenid plastids are derived from a Pyramimonas-related prasinophyte alga [6].A common euglenozoan feature is the processing of primary nuclear transcripts by spliced leader (SL) RNA-mediated trans-splicing [7]. This process includes replacement of the 5 0 -end of premRNA by the 5 0 -end of SL-RNA, donating identical 5 0 -termini to the mRNA molecules. Similar to nuclear cis-splicing, trans-splicing process is also mediated by spliceosomes, but a Y-branch intron structure is formed instead of a lariat [8]. The only currently known nuclear mRNA lacking the SL sequence in E. gracilis is that of the fibrillarin gene [9]. Since SL-trans-splicing does not occur in organelles (mitochondria, plastids), the presence (or absence) of an SL sequence at the 5 0 -end of a euglenozoan mRNA is diagnostic for its synthesis in the nucleus (or organelles, respectively).E. gracilis cell possesses approximately eight secondary plastids bounded by three membranes [10,11]. The plastid genome of this species is circular and comprises 143.17 kb. It contains 96 protein and RNA gene loci [12], group II and III introns, and twintrons (i.e. introns within introns) [13].The evolutionary transition from an endosymbiont to the plastid organelle was accompanied by a loss of many genes and gene transfer from the endosymbiont genome(s) to the host genome [14]. Gene transfer from plastids and mitochondria is an ongoing process, as it has been demonstrated in animals, plants, fungi as well as protists [15,16].Nuclear copies of plastid DNA (NUPT) can be found in a variety of species [17]. However, some species, e.g. the ...

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“…The synthesis of chloroplast nucleic acids, nucleic acid metabolizing enzymes and components of the chloroplast protein synthetic machinery are light regulated. The amount of chloroplast DNA per cell (Chelm et al 1977a;Hussein et al 1982;Rawson and Boerma 1976a;Srinivas and Lyman 1980) increases two to threefold after exposure of dark grown Euglena to light. Alkaline DNAse, a nuclear encoded cytoplasmically synthesized enzyme that hydrolyzes both single stranded DNA and RNA (Egan and Carell 1972;Egan et al 1975;Small and Sturgen 1976) is induced by light.…”

Section: Photocontrol Of Chloroplast Developmentmentioning

confidence: 99%

“…The relative amount of specific transcripts, ratio of one transcript to another transcript, did not appear to change upon light exposure (Geimer et al 2009) indicating that the transcription rate of specific genes is not photoregulated but the transcription rate of all genes is increased to the same extent by light exposure. Chloroplast copy number increases two to threefold after exposure of dark grown Euglena to light (Chelm et al 1977a;Hussein et al 1982;Rawson and Boerma 1976a;Srinivas and Lyman 1980). If transcript abundance is limited by template availability rather than the transcription machinery, the nonselective light induced increase in transcript abundance of most chloroplast genes could be due to the increased chloroplast copy number.…”

Section: Does Light Regulate Chloroplast Gene Expression At the Transmentioning

confidence: 99%

Photo and Nutritional Regulation of Euglena Organelle Development

Schwartzbach

2017

Advances in Experimental Medicine and Biology

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Euglena can use light and CO, photosynthesis, as well as a large variety of organic molecules as the sole source of carbon and energy for growth. Light induces the enzymes, in this case an entire organelle, the chloroplast, that is required to use CO as the sole source of carbon and energy for growth. Ethanol, but not malate, inhibits the photoinduction of chloroplast enzymes and induces the synthesis of the glyoxylate cycle enzymes that comprise the unique metabolic pathway leading to two carbon, ethanol and acetate, assimilation. In resting, carbon starved cells, light mobilizes the degradation of the storage carbohydrate paramylum and transiently induces the mitochondrial proteins required for the aerobic metabolism of paramylum to provide the carbon and energy required for chloroplast development. Other mitochondrial proteins are degraded upon light exposure providing the amino acids required for the synthesis of light induced proteins. Changes in protein levels are due to increased and decreased rates of synthesis rather than changes in degradation rates. Changes in protein synthesis rates occur in the absence of a concomitant increase in the levels of mRNAs encoding these proteins indicative of photo and metabolic control at the translational rather than the transcriptional level. The fraction of mRNA encoding a light induced protein such as the light harvesting chlorophyll a/b binding protein of photosystem II, (LHCPII) associated with polysomes in the dark is similar to the fraction associated with polysomes in the light indicative of photoregulation at the level of translational elongation. Ethanol, a carbon source whose assimilation requires carbon source specific enzymes, the glyoxylate cycle enzymes, represses the synthesis of chloroplast enzymes uniquely required to use light and CO as the sole source of carbon and energy for growth. The catabolite sensitivity of chloroplast development provides a mechanism to prioritize carbon source utilization. Euglena uses all of its resources to develop the metabolic capacity to utilize carbon sources such as ethanol which are rarely in the environment and delays until the rare carbon source is no longer available forming the chloroplast which is required to utilize the ubiquitous carbon source, light and CO.

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Cellular content of chloroplast DNA and chloroplast ribosomal RNA genes in Euglena gracilis during chloroplast development

Cited by 36 publications

References 19 publications

Transcription program of the chloroplast genome of Euglena gracilis during chloroplast development

Transcription program of the chloroplast genome of Euglena gracilis during chloroplast development

A small portion of plastid transcripts is polyadenylated in the flagellate Euglena gracilis

Photo and Nutritional Regulation of Euglena Organelle Development

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