scholarly journals TCA1, a Single Nuclear-Encoded Translational Activator Specific for petA mRNA in Chlamydomonas reinhardtii Chloroplast

Genetics ◽  
2001 ◽  
Vol 159 (1) ◽  
pp. 119-132
Author(s):  
K Wostrikoff ◽  
Y Choquet ◽  
F-A Wollman ◽  
J Girard-Bascou
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Nuclear Gene ◽  
Photosynthetic Electron Transport ◽  
Cytochrome F ◽  
Coding Region ◽  
Reading Frame ◽  
Transport Chain ◽  
Nuclear Loci ◽  
Translational Activator ◽  
B6f Complex

Abstract We isolated seven allelic nuclear mutants of Chlamydomonas reinhardtii specifically blocked in the translation of cytochrome f, a major chloroplast-encoded subunit of the photosynthetic electron transport chain encoded by the petA gene. We recovered one chloroplast suppressor in which the coding region of petA was now expressed under the control of a duplicated 5′ untranslated region from another open reading frame of presently unknown function. Since we also recovered 14 nuclear intragenic suppressors, we ended up with 21 alleles of a single nuclear gene we called TCA1 for translation of cytochrome b6f complex petA mRNA. The high number of TCA1 alleles, together with the absence of genetic evidence for other nuclear loci controlling translation of the chloroplast petA gene, strongly suggests that TCA1 is the only trans-acting factor. We studied the assembly-dependent regulation of cytochrome f translation—known as the CES process—in TCA1-mutated contexts. In the presence of a leaky tca1 allele, we observed that the regulation of cytochrome f translation was now exerted within the limits of the restricted translational activation conferred by the altered version of TCA1 as predicted if TCA1 was the ternary effector involved in the CES process.

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

1994 ◽  
Vol 14 (9) ◽  
pp. 6171-6179 ◽  
Author(s):  
N R Sturm ◽  
R Kuras ◽  
S Büschlen ◽  
W Sakamoto ◽  
K L Kindle ◽  
...  
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Promoter Activity ◽  
Transcriptional Activity ◽  
Transcription Termination ◽  
Cytochrome F ◽  
Direct Repeats ◽  
Wild Type ◽  
Coding Region ◽  
Putative Promoter ◽  
Coding Regions

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.

scholarly journals A ppGpp-mediated brake on photosynthesis is required for acclimation to nitrogen limitation in Arabidopsis.

2021 ◽  
Author(s):  
Shanna Romand ◽  
Hela Abdelkefi ◽  
Cecile Lecampion ◽  
Mohamed Belaroussi ◽  
Melanie Dusenne ◽  
...  
Keyword(s):  
Gene Expression ◽  
Photosynthetic Activity ◽  
Nitrogen Starvation ◽  
Nuclear Gene ◽  
Photosynthetic Electron Transport ◽  
Chloroplast Gene Expression ◽  
Photosynthetic Electron Transport Chain ◽  
Nuclear Gene Expression ◽  
Stress Acclimation ◽  
Transport Chain

Guanosine pentaphosphate and tetraphosphate (together referred to as ppGpp) are hyperphosphorylated nucleotides found in bacteria and the chloroplasts of plants and algae. In plants and algae artificial ppGpp accumulation can inhibit chloroplast gene expression, and influence photosynthesis, nutrient remobilisation, growth, and immunity. However, it is so far unknown whether ppGpp is required for abiotic stress acclimation in plants. Here, we demonstrate that ppGpp biosynthesis is necessary for acclimation to nitrogen starvation in Arabidopsis. We show that ppGpp is required for remodeling the photosynthetic electron transport chain to downregulate photosynthetic activity and for protection against oxidative stress. Furthermore, we demonstrate that ppGpp is required for coupling chloroplastic and nuclear gene expression during nitrogen starvation. Altogether, our work indicates that ppGpp is a pivotal regulator of chloroplast activity for stress acclimation in plants.

The Expression of Subunits of the Mitochondrial Complex I-Homologous NAD(P)H-Plastoquinone-Oxidoreductase during Plastid Development

1997 ◽  
Vol 52 (7-8) ◽  
pp. 481-486 ◽  
Keyword(s):  
Electron Transport ◽  
Complex I ◽  
Electron Transport Chain ◽  
Developmental Stages ◽  
Photosynthetic Electron Transport ◽  
Cytochrome F ◽  
Plastid Development ◽  
Photosynthetic Electron Transport Chain ◽  
Nadh Ubiquinone Oxidoreductase ◽  
Transport Chain

Abstract Plastids contain a NAD(P)H-plastoquinone-oxidoreductase which is homologous to the eubacterial and mitochondrial NADH-ubiquinone-oxidoreductase (complex I), but the meta­bolic function of the enzyme is still not yet understood. The enzyme consists of at least eleven subunits (NDH-A-K), which are all encoded in the plastid chromosome. In this study we have investigated the tissue-specific and light-dependent expression of the subunits NDH-H and NDH-K in maize, rice and mustard by western blot analysis. No NDH-proteins were found in root tissue, indicating that the presence of the enzyme is confined to leaf plastids. Analysis of the expression during the light-dependent development from etioplasts to chloro­plasts showed that high amounts of NDH-H and -K are present in etioplasts. The same result was found for subunits of the ATPase. In contrast, components of the photosynthetic electron transport chain (PSII-B, cytochrome f and PSI-D) accumulated only after illumination. In an second investigation, the expression of NDH-proteins along the natural chloroplast develop­ mental gradient from proplastids to chloroplasts in light-grown maize leaves was analysed. NDH-H and NDH-K as well as the ATPase were present at the youngest stages of chloro­plast development, while the massive accumulation of subunits of the photosystems and the cytochrome b6/f-complex took place in older leaf sections. We conclude from these studies that a functional NAD(P)H-plastoquinone-oxidoreductase is present in etioplasts and devel­oping plastids. We suggest that the enzyme serves the generation of a proton gradient across the prothylakoid membrane that is necessary for protein integration into the membrane at developmental stages where a functional photosynthetic electron transport chain is not yet operating.

scholarly journals Multiple Translational Control Sequences in the 5′ Leader of the Chloroplast psbC mRNA Interact With Nuclear Gene Products in Chlamydomonas reinhardtii

Genetics ◽  
2003 ◽  
Vol 163 (3) ◽  
pp. 895-904
Author(s):  
William Zerges ◽  
Andrea H Auchincloss ◽  
Jean-David Rochaix
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Reporter Gene ◽  
Translational Control ◽  
Nuclear Gene ◽  
Gene Products ◽  
Wild Type ◽  
Translation Initiation Region ◽  
Mrna Stabilization ◽  
In The Wild ◽  
Nuclear Loci

Abstract Translation of the chloroplast psbC mRNA in the unicellular eukaryotic alga Chlamydomonas reinhardtii is controlled by interactions between its 547-base 5′ untranslated region and the products of the nuclear loci TBC1, TBC2, and possibly TBC3. In this study, a series of site-directed mutations in this region was generated and the ability of these constructs to drive expression of a reporter gene was assayed in chloroplast transformants that are wild type or mutant at these nuclear loci. Two regions located in the middle of the 5′ leader and near the initiation codon are important for translation. Other deletions still allow for partial expression of the reporter gene in the wild-type background. Regions with target sites for TBC1 and TBC2 were identified by estimating the residual translation activity in the respective mutant backgrounds. TBC1 targets include mostly the central part of the leader and the translation initiation region whereas the only detected TBC2 targets are in the 3′ part. The 5′-most 93 nt of the leader are required for wild-type levels of transcription and/or mRNA stabilization. The results indicate that TBC1 and TBC2 function independently and further support the possibility that TBC1 acts together with TBC3.

scholarly journals The PET54 gene of Saccharomyces cerevisiae: characterization of a nuclear gene encoding a mitochondrial translational activator and subcellular localization of its product.

Genetics ◽  
1989 ◽  
Vol 122 (2) ◽  
pp. 297-305 ◽  
Author(s):  
M C Costanzo ◽  
E C Seaver ◽  
T D Fox
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Nuclear Gene ◽  
Open Reading Frames ◽  
Gene Encoding ◽  
Reading Frame ◽  
Acid Protein ◽  
Translational Activator ◽  
The Right ◽  
A Minor

Abstract The product of the nuclear Saccharomyces cerevisiae gene PET54 is specifically required, along with at least two other nuclear gene products, for translation of the mitochondrial mRNA encoding subunit III of cytochrome c oxidase (coxIII). We have genetically mapped PET54 (to the right arm of chromosome VII, 4.8 cM centromere-distal to SUF15), and have biochemically characterized the gene and its product. We determined the nucleotide sequence of a 1.6-kb DNA fragment carrying PET54 and identified the PET54 reading frame by determining the sequence of an ochre mutant allele as well as frameshift and frameshift-revertant alleles of the gene. The wild-type PET54 gene encodes a slightly basic 293-amino acid protein. PET54 is expressed from two mRNAs, both with unusual features: a major transcript with an extremely short 5'-untranslated leader, and a minor transcript with a relatively long 5'-leader carrying three short open reading frames. Antiserum raised against a trpE-PET54 fusion protein was used to probe subcellular fractions. These experiments showed that the PET54 protein is specifically associated with mitochondria, suggesting that it is likely to act directly in coxIII translation.

scholarly journals Targeted disruption of the NIT8 gene in Chlamydomonas reinhardtii.

1995 ◽  
Vol 15 (10) ◽  
pp. 5762-5769 ◽  
Author(s):  
J A Nelson ◽  
P A Lefebvre
Keyword(s):  
Homologous Recombination ◽  
Chlamydomonas Reinhardtii ◽  
Marker Gene ◽  
Nuclear Gene ◽  
Genomic Region ◽  
Coding Region ◽  
Targeted Disruption ◽  
Targeted Gene Disruption ◽  
Nitrate And Nitrite ◽  
Endogenous Locus

We have used homologous recombination to disrupt the nuclear gene NIT8 in Chlamydomonas reinhardtii. This is the first report of targeted gene disruption of an endogenous locus in C. reinhardtii and only the second for a photosynthetic eukaryote. NIT8 encodes a protein necessary for nitrate and nitrite assimilation by C. reinhardtii. A disruption vector was constructed by placing the CRY1-1 selectable marker gene, which confers emetine resistance, within the NIT8 coding region. nit8 mutants are unable to grow on nitrate as their sole nitrogen source (Nit-) and are resistant to killing by chlorate. One of 2,000 transformants obtained after selection on emetine-chlorate medium contained a homologous insertion of five copies of the disruption plasmid into the NIT8 gene, producing an emetine-resistant, chlorate-resistant Nit- phenotype. The mutant phenotype was rescued by the wild-type NIT8 gene upon transformation. Seven other mutations at the nit8 locus, presumably resulting from homologous recombination with the disruption plasmid, were identified but were shown to be accompanied by deletions of the surrounding genomic region.

scholarly journals Genetic Analysis of Chloroplast c-Type Cytochrome Assembly in Chlamydomonas reinhardtii: One Chloroplast Locus and at Least Four Nuclear Loci Are Required for Heme Attachment

Genetics ◽  
1998 ◽  
Vol 148 (2) ◽  
pp. 681-692
Author(s):  
Zhiyi Xie ◽  
Duane Culler ◽  
Beth Welty Dreyfuss ◽  
Richard Kuras ◽  
Francis-Andre Wollman ◽  
...  
Keyword(s):  
Genetic Analysis ◽  
Chlamydomonas Reinhardtii ◽  
Nuclear Genome ◽  
Protein Product ◽  
Cytochrome F ◽  
The Other ◽  
Uniparental Inheritance ◽  
Cytochrome C6 ◽  
Nuclear Loci

Abstract Chloroplasts contain up to two c-type cytochromes, membrane-anchored cytochrome f and soluble cytochrome c6. To elucidate the post-translational events required for their assembly, acetate-requiring mutants of Chlamydomonas reinhardtii that have combined deficiencies in both plastid-encoded cytochrome f and nucleus-encoded cytochrome c6 have been identified and analyzed. For strains ct34 and ct59, where the phenotype displays uniparental inheritance, the mutations were localized to the chloroplast ccsA gene, which was shown previously to be required for heme attachment to chloroplast apocytochromes. The mutations in another eight strains were localized to the nuclear genome. Complementation tests of these strains plus three previously identified strains of the same phenotype (ac206, F18, and F2D8) indicate that the 11 ccs strains define four nuclear loci, CCS1–CCS4. We conclude that the products of the CCS1–CCS4 loci are not required for translocation or processing of the preproteins but, like CcsA, they are required for the heme attachment step during assembly of both holocytochrome f and holocytochrome c6. The ccsA gene is transcribed in each of the nuclear mutants, but its protein product is absent in ccs1 mutants, and it appears to be degradation susceptible in ccs3 and ccs4 strains. We suggest that Ccs1 may be associated with CcsA in a multisubunit “holocytochrome c assembly complex,” and we hypothesize that the products of the other CCS loci may correspond to other subunits.

Characterization of Cytochrome f Mutants in the b6f- Complex of Chlamydomonas Reinhardtii

1998 ◽  
pp. 1549-1552
Author(s):  
F. Baymann ◽  
F. Zito ◽  
R. Kuras ◽  
W. Nitschice ◽  
P. Joliot ◽  
...  
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Cytochrome F ◽  
B6f Complex
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