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At least 19 recordsLinked to original sources
PubMed1975

Chloroplast genes in Chlamydomonas affecting organelle ribosomes. Genetic and biochemical analysis of analysis of antibiotic-resistant mutants at several gene loci.

Six chloroplast gene mutants of Chlamydomonas reinhardtii resistant to spectinomycin, erythromycin, or streptomycin have been assessed for antibiotic resistance of their chloroplast ribosomes. Four of these mutations clearly confer high levels of antibiotic resistance on the chloroplast ribosomes both in vivo. Although one mutant resistant to streptomycin and one resistant to spectinomycin have chloroplast ribosomes as sensitive to antibiotics as those of wild type in vivo, these mutations can be shown to alter the wildtype sensitivity of chloroplast ribosomes in polynucleotide-directed amino acid incorporation in vitro. Genetic analysis of these six chloroplast mutants and three similar mutants (Sager, 1972), two of which have been shown to affect chloroplast ribosomes (Mets and Bogorad, 1972; Schlanger and Sager, 1974), indicates that in Chlamydomonas at least three chloroplast gene loci can affect streptomycin resistance of chloroplast ribosomes and that two can affect erythromycin resistance. The three spectinomycin-resistant mutants examined appear to be alleles at a single chloroplast gene locus, but may represent mutations at two different sites within the same gene. Unlike wild type, the streptomycin and spectinomycin resistant mutants which have chloroplast ribosomes sensitive to antibiotics in vivo, grow well in the presence of antibiotic by respiring exogenously supplied acetate as a carbon source, and have normal levels of cytochrome oxidase activity and cyanide-sensitive respiration. We conclude that mitochondrial protein synthesis in these mutants is resistant to these antibiotics, whereas in wild type it is sensitive. To explain the behavior of these two chloroplast gene mutants as well as other one-step mutants which are resistant both photosynthetically and when respiring acetate in the dark, we have postulated that a mutation in a single chloroplast gene may result in alteration of both chloroplast and mitochondrial ribosomes. Mitochondrial resistance would appear to be the minimal necessary condition for survival of all such mutants, and antibiotic-resistant chloroplast ribosomes would be necessary for survival only under photosynthetic conditions.

Chlamydomonas↗
PubMed2025

Bundle sheath cell-specific expression of chloroplast genes encoding subunits of the NADH dehydrogenase-like complex in maize.

C4 photosynthesis alleviates the limitation caused by the oxygenase activity of Rubisco by partitioning photosynthetic functions between two distinct cell types: bundle sheath cells (BSCs) and mesophyll cells (MCs). These cell types perform different steps of photosynthesis using specialized machinery, accompanied by differential expression of chloroplast genes. To uncover the underlying molecular mechanisms for this differentiation, we isolated BSCs and MCs and compared their chloroplast transcriptomes, focusing on the chloroplast NADH dehydrogenase-like (NDH) complex, which is enriched in BSCs. To investigate whether RNA stabilization contributes to differential gene expression, we analyzed RNA footprints that reflect the binding of pentatricopeptide repeat (PPR) proteins to their RNA targets. We could not detect cell-type-specific accumulation of footprint RNAs. We then focused on transcriptional regulation, specifically on an operon that starts with the rps15 gene. The operon includes six ndh genes and the psaC gene encoding a photosystem I subunit. Transcript levels of all genes in this operon were higher in BSCs than in MCs, suggesting coordinated regulation as a transcriptional unit. Based on the genomic location of the rps15 gene within inverted repeats near the junctions on both sides of the small single copy region, we demonstrated that rps15, through two distinct promoters, is sufficient to drive preferential accumulation of downstream transcripts in BSCs.

Zea mays↗
PubMed1977

Identification and cloning of the chloroplast gene coding for the large subunit of ribulose-1,5-bisphosphate carboxylase from Chlamydomonas reinhardi.

mRNA coding for the large subunit (LS) of ribulose-1,5-bisphosphate carboxylase [3-phospho-D-glycerate carboxy-lyase (dimerizing), EC 4.1.1.39] from Chlamydomonas reinhardi has been isolated from small polyribosomes immunoadsorbed to column-bound anti-LS antibody. 32P-Labeled LS mRNA was used as a hybridization probe to detect LS genes. The probe hybridized to C. reinhardi chloroplast DNA and at hybridization saturation revealed that there are approximately 75 LS genes per chloroplast. When chloroplast DNA was digested with the restriction endonuclease EcoRI and the fragments were transferred to a nitrocellulose filter, the LS mRNA probe hybridized to a DNA fragment of molecular weight 3.2 X 10(6). This same fragment codes (in part) for 16S and 23S chloroplast rRNAs, which are also coded (in part) by fragments of molecular weights 9.0, 2.3, and 0.4 X 10(6). The restriction fragment containing the LS gene has been cloned in the Escherichia coli plasmid pMB9.

Carboxy-Lyases↗
PubMed1977

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

The cellular content of chloroplast DNA in Euglena gracilis has been quantitatively determined. DNA was extracted from Euglena cells at various stages of chloroplast development and renatured in the presence of trace amounts of 3H-labeled chloroplast DNA. From the kinetics of renaturation of the 3H-labeled chloroplast DNA, compared with the kinetics of renaturation of excess nonradioactive chloroplast DNA, the fraction of cellular DNA represented by chloroplast DNA was calculated. The content of chloroplast DNA was found to increase from 4.9 to 14.6% of cellular DNA during light-induced chloroplast development. Correcting for the change in DNA mass per cell, the number of copies of chloroplast DNA is found to vary from 1400 to 2900 per cell. During this developmental transition, the cellular content of the chloroplast ribosomal RNA genes varies from 1900 to 5200 copies per cell. The ratio of the number of copies of rRNA genes to chloroplast genomes per cell remains in the range of 1-2 throughout chloroplast development, ruling out selective amplification of chloroplast rRNA genes as a means of regulation of rRNA gene expression. Direct measurement of the number of rRNA cistrons per 9.2 X 10(7) dalton genome yields a value of 1 or 2.

Animals↗
PubMed1979

Isolation of Euglena gracilis chloroplast 5S ribosomal RNA and mapping the 5S rRNA gene on chloroplast DNA.

Ribosomal RNA (5S) from Euglena gracilis chloroplasts was isolated by preparative electrophoresis, labeled in vitro with 125I, and hybridized to restriction nuclease fragments from chloroplast DNA or cloned chloroplast DNA segments. Euglena chloroplast 5S rRNA is encoded in the chloroplast genome. The coding region of 5S rRNA has been positioned within the 5.6 kilobase pair (kbp) repeat which also codes for 16S and 23S rRNA. There are three 5S rRNA genes on the 130-kbp genome. The order of RNAs within a single repeat is 16S-23S-5S. The organization and size of the Euglena chloroplast ribosomal repeat is very similar to the ribosomal RNA operons of Escherichia coli.

Chloroplasts↗
PubMed1977

Expression of the chloroplast ribosomal RNA genes of Euglena gracilis during chloroplast development.

The cellular content and transcription program of the chloroplast ribosomal RNA genes of Euglena gracilis Z have been determined during the light-induced development of chloroplasts by hybridization of total cell DNA or RNA to purified 3H-labeled chloroplast ribosomal DNA ([3H]ctrDNA). Pancreatic DNase activated, partially purified chloroplast rDNA was enzymatically labeled in vitro by E. coli DNA polymerase I with [3H]TTP as a substrate. The [3H] DNA was denatured and hybridized with a vast excess of purified chloroplast 16 and 23S rRNA. The rRNA-[3H]ct rCNA hybrid was isolated by chromatography on hydroxylapatite. The [3H]ct rDNA was purified and characterized by the kinetics of its renaturation with chloroplast DNA and rRNA, and by the thermal stability of [3H]DNA-DNA and [3H]DNA-RNA hybrids. [3H]ct rDNA was hybridized in trace amounts to cellular RNA or DNA isolated from Euglena cells 0,4,8,12,24,48, and 72 h after the onset of chloroplast development. From a comparison of the kinetics of hybridization with hybridization of standards of known kinetic complexity quantitative estimates of the cellular rRNA and rDNA gene content were made. Chloroplast rRNA increases from 2 to 26% of the cellular RNA during development, while the percentage of cellular DNA represented by ct rDNA increases two- to threefold. Correcting for the change in cellular RNA and DNA content during development, the number of copies of the rRNA gene increases less than twofold, while the number of copies of rRNA per cell increases sixfold. The results are consistent with either a transcriptional activation of the ribosomal genes or an increased rRNA stability during developmental.

Animals↗
PubMed2025

A melon (Cucumis melo) homologue of REPRESSOR OF PHOTOSYNTHETIC GENES prevents chloroplast differentiation in the fruit flesh.

Fruit flesh color in melon can be orange, green or white, depending on the accumulation of the orange carotenoid β-carotene or / and green chlorophylls. The dominant allele of Green flesh (Gf) causes orange melons, but in the absence of this allele the flesh of ripe melon can be white or green depending on the White flesh (Wf) locus, being white dominant over green. The identity of Wf has remained unclear despite several candidates have been proposed. Here we identified Wf by fine mapping of a segregating population derived from the white-fleshed variety Piel de Sapo (PS, gf gf / Wf Wf) and the orange-fleshed Védrantais (VED, Gf Gf / wf wf). Wf corresponds to the gene MELO3C003098, herein referred to as CmRPGE1 as it encodes a fruit-specific homologue of REPRESSOR OF PHOTOSYNTHETIC GENES (RPGE) microproteins. Similar to RPGE homologues from other plants, overexpression of the PS allele (CmRPGE1 PS ) caused a pale green leaf phenotype in Nicotiana benthamiana and Arabidopsis thaliana. By contrast, a 10-nucleotide deletion in the VED allele (CmRPGE1 VED ) resulted in a loss of RPGE function. The active CmRPGE1PS microprotein interacts with a fruit-localized melon homologue of ARABIDOPSIS PSEUDO-RESPONSE REGULATOR2 (APRR2), a GARP family transcription factor. Binding of CmRPGE1PS retains the melon APRR2 homologue in the cytosol, hence preventing the regulation of target genes involved in chloroplast biogenesis. In green fruit cultivars, the non-functional CmRPGE1VED allele allows APRR2 to perform its function, leading to chloroplast development and consequently a green flesh phenotype.

Biological Sciences – Plant Biology↗
PubMed2026

Molecular investigation of the progenitors, origin and domestication patterns of diploid Chinese old garden roses.

BACKGROUND AND AIMS: Chinese old garden roses are major contributors to the genetic development of modern roses. The RoKSN gene is associated with continuous flowering in roses and is proposed to have originated from Chinese wild roses. However, the wild roses that are implicated in the breeding of Chinese old garden roses and the origin of the RoKSN locus remain unidentified. We collected 25 of the most renowned and classic diploid Chinese old garden roses along with all related wild roses from East Asia. These roses were analysed with the aim of identifying the wild species that contributed to the genetic composition of Chinese old garden roses. In addition, we aimed to infer the geographical origin of the RoKSN gene and to develop a schematic overview of hybrid domestication of Chinese old garden roses. METHODS: We compared the haplotypes of internal transcribed spacers (nrITS), six nuclear single-copy genes and three chloroplast genes between Chinese old garden roses and wild roses. Additionally, we assessed genetic organization using 21 expressed sequence tag-simple sequence repeats to identify potential donor species that contributed to the emergence of these cultivars. Primers were designed for RoKSN to allow comparison of the gene across the entire distribution range of Rosa sect. Chinenses. KEY RESULTS: Our findings confirmed that the majority of rose cultivars are descendants of early hybridization events. Rosa chinensis var. spontanea, R. odorata var. gigantea and R. multiflora var. cathayensis were the primary donors for the 25 cultivar roses. Chinese old garden roses were categorized into four groups. Ten cultivars were hybrids between R. chinensis var. spontanea and R. multiflora var. cathayensis, thereby forming the 'Old Blush' group. Five cultivars were hybrids between 'Old Blush' and the R. kwangtungensis species complex, thereby forming the 'Slater's crimson' group. Six cultivars were hybrids between 'Old Blush' and R. odorata var. gigantea, thereby forming the 'Tea Rose' group, and three cultivars were hybrids that evolved from more than three donors. Moreover, we observed relatively close genetic proximity among Chinese old garden roses with an identical RoKSN-copia gene that is responsible for continuous flowering, which indicates a single origin for this retrotransposon-containing allele. Additionally, we determined that the haplotypes of the RoKSN-copia gene predominantly occurred in the Sichuan Basin region. In contrast, R. chinensis cultivated in the Ya'an region showed no markers of hybridization and displayed a genetic composition that was close to that of the wild species R. chinensis var. spontanea. This cultivar may represent the earliest mutated individual that bears the RoKSN-copia gene and may have served as a bridge from wild species to continuous-flowering old rose cultivars. CONCLUSIONS: The study provides crucial evidence that elucidates the origin of cultivated roses and lays the groundwork for further analysis of the breeding history of Chinese old garden roses using genomic data.

Domestication↗
PubMed1977

Cloned ribosomal RNA genes from chloroplasts of Euglena gracilis.

Fragments of Euglena chloroplast DNA generated by endonuclease R-Eco RI were separated by agarose-gel electrophoresis into 24 distinct bands. At least five fragments contain sequences complementary to chloroplast ribosomal RNA, Most of the Eco RI fragments have been cloned in a plasmid of Escherichia coli. Three of the cloned fragments were shown to contain chloroplast ribosomal RNA sequences by DNA-RNA hybridization.

Chloroplasts↗
PubMed1978

Localization of 4S RNA genes on the chloroplast genome of Chlamydomonas reinhardii.

The genes coding for 4S RNA have been localized on the physical map of the chloroplast genome of Chlamydomonas reinhardii by hybridizing 32P-labelled 4S RNA to EcoRI, BamHI, Bg1II and Hind III chloroplast DNA digests and to hybrid plasmids containing EcoRI and Bam HI chloroplast DNA fragments. At least 10 EcoRI and 7 Bam HI fragments carry sequences coding for 4S RNA. These genes are interspersed throughout the genome. The spacer between the 16S and 23S ribosomal RNA genes, which is repeated twice per chloroplast DNA molecule, codes for at least one 4S RNA, shown to be transcribed from the same strand as the ribosomal RNAs.

Chlamydomonas↗
PubMed1979

Structure analysis at the ends of the intervening DNA sequences in the chloroplast 23S ribosomal genes of C. reinhardii.

All of the chloroplast 23S ribosomal genes of C. reinhardii are interrupted by a 0.87 kb sequence (Rochaix and Malnoë, 1978). We have sequenced the DNA across the two ends of this intervening element. In parallel, we have examined the nucleotide sequences in the corresponding part of the 23S ribosomal RNA. This allowed us to locate precisely the boundaries between the coding (that is, transcribed into mature 23S rRNA) and the noncoding DNA. The results show that the intervening sequence is flanked by two identical sets of 3 bp (5'-CGT) oriented as direct repeats. In addition, a sequence of 5 bp (5'-CGTGA) lies exactly next to one end and is found very close (16 bp) to the other end, in the coding part of the gene. These two sets are also oriented as direct repeats. Finally, sequences near one end of the intervening element are found with a few alterations near the other end, but in an inverted orientation. Possible interpretations of these results are discussed.

Base Sequence↗
PubMed2026

The complete Chloroplast Genome of Dianthus Helenae, an Endemic Species with Medicinal Potential from the Nuratau Mountains, Uzbekistan.

Dianthus helenae Vved. is an endemic medicinal species of the Nuratau Mountains, Uzbekistan, and its genomic resources have remained largely unavailable. In this study, we sequenced, assembled, and characterized the complete chloroplast genome of D. helenae and evaluated its phylogenetic position within Dianthus. The plastome exhibited a typical circular quadripartite structure with a total length of 149,567 bp, comprising a large single-copy (LSC) region of 82,856 bp, a small single-copy (SSC) region of 17,105 bp, and a pair of inverted repeats (IRs) of 24,803 bp each. The genome contained the typical set of chloroplast genes, including protein-coding genes, transfer RNAs, and ribosomal RNAs, with duplicated genes located in the IR regions. Phylogenetic analysis based on complete chloroplast genome sequences strongly supported the placement of D. helenae within Dianthus and recovered it as a distinct lineage relative to other sampled species. Sliding window analysis of nucleotide diversity revealed uneven sequence variation across the plastome, with higher variability in the SSC and LSC regions than in the IRs. Several highly variable loci, including trnK-UUU , rps16-trnQ-UUG , rpl32, ycf1, and ndh-associated regions, were identified as potential molecular markers. These results provide an important genomic resource for Dianthus and establish a foundation for future phylogenetic, taxonomic, conservation, and molecular identification studies of this endemic Central Asian species.

Genome, Chloroplast↗
PubMed1979

Mutations in nine chloroplast loci of Chlamydomonas affecting different photosynthetic functions.

Chloroplast components known to be coded by chloroplast DNA include chloroplast rRNAs, tRNAs, and the large subunit of ribulose-bisphosphate carboxylase. Because these components comprise less than 3% of the estimated coding capacity of the chloroplast genome, most chloroplast gene functions have yet to be identified. One approach to this problem is the isolation and characterization of mutations in the chloroplast genome affecting specific photosynthetic functions. Recently we have found that such mutations can be preferentially recovered by using arsenate selection on cells previously grown in 5-fluorodeoxyuridine. Sixteen mutants thus isolated have been localized into nine chloroplast loci, based on their ability to recombine and produce photosynthetically competent progeny. Mutants at two loci show the characteristic syndrome of photosynthetic defects that results from a deficiency in chloroplast protein synthesis. These have been found to lack chloroplast ribosome monomers. Mutants at three loci are missing chlorophyll-protein complex I in their thylakoid membranes. Mutants at three other loci are deficient in membrane polypeptides known to be associated with the chloroplast coupling factor.

Alleles↗
PubMed1978

The non-reciprocality of organelle gene recombination in Chlamydomonas reinhardtii and Saccharomyces cerevisiae: some new observations and a restatement of some old problems.

Organelle recombinant genotype frequencies, derived from analysis of individual mitotic zygote clones of Chlamydomonas reinhardtii and Saccharomyces cerevisiae, were subjected to two types of statistical tests in an attempt to detect the occurrence of reciprocal recombination: (i) calculation of correlation coefficients for the frequencies of two recombinant genotypes (reciprocal or non-reciprocal pairs) within individual zygote clones, and (ii) application of the chi-square test for independence to the frequencies of zygotes yielding one or the other, neither, or both of a given recombinant pair. Applying test (i), the strongest correlations are found for non-reciprocal rather than reciprocal pairs. When the data are analyzed by method (ii), some reciprocal as well as non-reciprocal pairs appear to be produced concurrently in zygote clones. However, such deviations from independence are greatest for non-reciprocal pairs. These tests yield comparable results for yeast mitochondrial and Chlamydomonas chloroplast gene recombination, and provide no convincing evidence for reciprocal genetic exchange. Explanations for the observed lack of reciprocality are discussed with reference both to our present understanding of the molecular events responsible for genetic recombination, and to the problems which may be unique to the analysis of organelle gene recombination.

Chlamydomonas↗
PubMed1978

Uniparental inheritance of mitochondrial genes in yeast: dependence on input bias of mitochondrial DNA and preliminary investigations of the mechanism.

In Saccharomyces cerevisiae, previous studies on the inheritance of mitochondrial genes controlling antibiotic resistance have shown that some crosses produce a substantial number of uniparental zygotes, which transmit to their diploid progeny mitochondrial alleles from only one parent. In this paper, we show that uniparental zygotes are formed especially when one parent (majority parent) contributes substantially more mitochondrial DNA molecules to the zygote than does the other (minority) parent. Cellular contents of mitochondrial DNA (mtDNA) are increased in these experiments by treatment with cycloheximide, alpha-factor, or the uvsp5 nuclear mutation. In such a biased cross, some zygotes are uniparental for mitochondrial alleles from the majority parent, and the frequency of such zygotes increases with increasing bias. In two- and three-factor crosses the cap1, ery1, and oli1 loci behave coordinately, rather than independently; minority markers tend to be transmitted or lost as a unit, suggesting that the uniparental mechanism acts on entire mtDNA molecules rather than on individual loci. This rules out the possibility that uniparental inheritance can be explained by the conversion of minority markers to the majority alleles during recombination. Exceptions to the coordinate behavior of different loci can be explained by marker rescue via recombination. Uniparental inheritance is largely independent of the position of buds on the zygote. We conclude that it is due to the failure of minority markers to replicate in some zygotes, possibly involving the rapid enzymatic destruction of such markers. We have considered two general classes of mechanisms: (1) random selection of molecules for replication, as for example by competition for replicating sites on a membrane; and (2) differential marking of mtDNA molecules in the two parents, possibly by modification enzymes, followed by a mechanism that "counts" molecules and replicates only the majority type. These classes of models are distinguished genetically by the fact that the first predicts that the output frequency of a given allele among the progeny of a large number of zygotes will approximately equal the average input frequency of that allele, while the second class predicts that any input bias will be amplified in the output. The data suggest that bias amplification does occur. We hypothesize that maternal inheritance of mitochondrial or chloroplast genes in many organisms may depend upon a biased input of organelle DNA molecules, which usually favors the maternal parent, followed by failure of the minority (paternal) molecules to replicate in many or all zygotes.

Alleles↗