Organization and structure of plastome psbF, psbL, petG and ORF712 genes in Chlamydomonas reinhardtii

Fong, Steven E.; Surzycki, Stefan

doi:10.1007/bf00351664

Cited by 33 publications

(26 citation statements)

References 20 publications

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“…This finding contradicts a general belief that Chlamydomonas has relatively few polycistronic gene clusters (Barkan and Goldschmidt-Clermont, 2000). The second factor contributing to the large transcriptome are three large open reading frames, rpoC2, ORF1995, and ORF2971 (Fong and Surzycki, 1992;Boudreau et al, 1997), although their transcript termini have not been defined. Overall, this global approach revealed a densely transcribed genome in which the extent of polycistronic units resulted in a 20% difference between the approximate amount of DNA transcribed and the DNA that encodes the amino acids of expressed proteins.…”

Section: R E T R a C T E Dmentioning

confidence: 59%

Retracted: The Chlamydomonas reinhardtii Organellar Genomes Respond Transcriptionally and Post-Transcriptionally to Abiotic Stimuli

2002

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The Chlamydomonas reinhardtii plastid and mitochondrial transcriptomes were surveyed for changes in RNA profiles resulting from growth in 12 culture conditions representing 8 abiotic stimuli. Organellar RNA abundance exhibited marked changes during nutrient stress and exposure to UV light, as revealed by both RNA gel blot and DNA microarray analyses. Of particular note were large increases in tufA and clpP transcript abundance during nutrient limitation. Phosphate and sulfur limitation resulted in the most global, yet opposite, effects on organellar RNA abundance, changes that were dissected further using run-on transcription assays. Removal of sulfate from the culture medium, which is known to reduce photosynthesis, resulted in 2-fold to 10-fold decreases in transcription rates, which were reflected in lower RNA abundance. The decrease in transcriptional activity was completely reversible and recovered to twice the control level after sulfate replenishment. Conversely, phosphate limitation resulted in a twofold to threefold increase in RNA abundance that was found to be a post-transcriptional effect, because it could be accounted for by increased RNA stability. This finding is consistent with the known metabolic slowdown under phosphate stress. Additionally, inhibitor studies suggested that unlike those in higher plants, Chlamydomonas chloroplasts lack a nucleusencoded plastid RNA polymerase. The apparently single type of polymerase could contribute to the rapid and genomewide transcriptional responses observed within the chloroplast.

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Section: R E T R a C T E Dmentioning

confidence: 59%

Retracted: The Chlamydomonas reinhardtii Organellar Genomes Respond Transcriptionally and Post-Transcriptionally to Abiotic Stimuli

2002

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“…In some instances, the gene order within clusters can be aligned with operons in the Euglena gracilis chloroplast and Escherichia coli genomes. In the unicellular green alga Chlamydomonas reinhardtii, the genetic content of the chloroplast genome is similar to that of higher plants, but the gene order is different (9,14). In contrast to higher plants, only two instances of cotranscription have been well documented, one in which the psbD gene is cotranscribed with exon II of psaA (8) and the other in which psbB is cotranscribed with a conserved open reading frame, ORF31 (18,28).…”

mentioning

confidence: 99%

The petD gene is transcribed by functionally redundant promoters in Chlamydomonas reinhardtii chloroplasts.

et al. 1994

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FUD6, a nonphotosynthetic mutant of Chlamydomonas reinhardtii, was previously found to be deficient in the synthesis of subunit IV of the cytochrome b6/f complex, the chloroplast petD gene product (C. Lemaire, J. Girard-Bascou, F.-A. Wollman, and P. Bennoun, Biochim. Biophys. Acta 851:229-238, 1986). The lesion in FUD6 is a 236-bp deletion between two 11-bp direct repeats in the chloroplast genome. It extends from 82 to 72 bp upstream of the 5' end of wild-type petD mRNA to 156 to 166 bp downstream of the 5' end. Thus, the deletion extends into the putative promoter and 5' untranslated region of petD. No petD mRNA of the normal size can be detected in FUD6 cells, but a low level of a dicistronic message accumulates, which contains the coding regions for subunit IV and cytochrome f, the product of the upstream petA gene. petD transcriptional activity in FUD6 is not significantly altered from the wild-type level. This transcriptional activity was eliminated by petA promoter disruptions, suggesting that it originates at the petA promoter. We conclude that the petD-coding portion of most cotranscripts is rapidly degraded in FUD6, possibly following processing events that generate the 3' end of petA mRNA. A chloroplast transformant was constructed in which only the sequence from -81 to -2 relative to the major 5' end of the petD transcript was deleted. Although this deletion eliminates all detectable petD promoter activity, the transformant grows phototrophically and accumulates high levels of monocistronic petD mRNA. We conclude that the petD gene can be transcribed by functionally redundant promoters. In the absence of a functional petD promoter, a lack of transcription termination allows the downstream petD gene to be cotranscribed with the petA coding region and thereby expressed efficiently.

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“…Previously, the sequence and location of petG in the C. reinhardtii chloroplast genome were reported (7). To investigate the function of petG, we deleted the gene from the chloroplast, inserting in its place a spectinomycin resistance cassette containing a Chlamydomonas atpA promoter region and the bacterial aadA gene (8).…”

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confidence: 99%

The Deletion of petG in Chlamydomonas reinhardtii Disrupts the Cytochrome bf Complex

Berthold

Schmidt

Malkin

1995

Journal of Biological Chemistry

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The 4-kDa protein encoded by chloroplast petG copurifies with the cytochrome bf complex of spinach and is found in a number of other photosynthetic organisms, including the eukaryotic alga Chlamydomonas reinhardtii. To determine whether petG is involved in the function or assembly of the cytochrome bf complex, the gene was cloned from C. reinhardtii, excised from the DNA fragment, and replaced with a spectinomycin resistance cassette. A petG deletion strain of C. reinhardtii was then obtained by biolistic transformation. The resulting homoplasmic petG deletion strains are unable to grow photosynthetically, and immunoblot analysis shows markedly decreased levels of cytochrome b 6 , cytochrome f, the Rieske iron-sulfur protein, and subunit IV. To verify that this phenotype was due to the removal of petG, we also constructed a strain with a deletion in the open reading frame (ORF56), which is found 25 base pairs downstream of petG. The ORF56 deletion strain grew photosynthetically and had wild-type levels of the four major cytochrome bf subunits. We conclude that the absence of the PetG protein affects either the assembly or stability of the cytochrome bf complex in C. reinhardtii.The cytochrome bf complex, found in green plants, eukaryotic algae, and cyanobacteria, serves to connect photosystem I to photosystem II in the chloroplast or cyanobacterial electron transfer chain. The complex functions as a plastoquinol:plastocyanin/cytochrome c 6 oxidoreductase, the rate-limiting step of the photosynthetic electron transport chain. These redox reactions are coupled to an efficient translocation of protons across the membrane; the resulting proton gradient provides a source of energy for the synthesis of ATP by the chloroplast or cyanobacterial ATP synthase (1-3).The cytochrome bf complex contains four large subunits.

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Organization and structure of plastome psbF, psbL, petG and ORF712 genes in Chlamydomonas reinhardtii

Cited by 33 publications

References 20 publications

Retracted: The Chlamydomonas reinhardtii Organellar Genomes Respond Transcriptionally and Post-Transcriptionally to Abiotic Stimuli

Retracted: The Chlamydomonas reinhardtii Organellar Genomes Respond Transcriptionally and Post-Transcriptionally to Abiotic Stimuli

The petD gene is transcribed by functionally redundant promoters in Chlamydomonas reinhardtii chloroplasts.

The Deletion of petG in Chlamydomonas reinhardtii Disrupts the Cytochrome bf Complex

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