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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Current genetics 12 (1987), S. 483-488 
    ISSN: 1432-0983
    Keywords: Chlamydomonas reinhardtii ; Photosystem I mutants ; Chloroplast recombination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In this work seven chloroplast mutations conferring a deficiency in photosystem I reaction centers have been mapped at four chloroplast loci in Chlamydomonas reinhardtii. Recombination frequencies were estimated from diploid progeny of vegetative zygotes. These four loci were scattered throughout the chloroplast genome. The three mutations at locus I were found to be tightly linked to a mutation in the rbcL gene coding for the large subunit of ribulose-1,5-bisphosphate carboxylase (Dron et al. 1983). As the psaA2 gene coding for one apoprotein of the chlorophyll-complex CPI, identified by its homology with the corresponding maize gene (Fish et al. 1985), has been found close to the rbcL gene (Dron et al. 1982), the psaA2 gene could be at locus 1.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0983
    Keywords: Nuclear gene ; Chloroplast gene expression ; psbA ; Chlamydomonas reinhardtii
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effect of the nuclear mutation F34 on the synthesis of chloroplast-encoded photosystem II (PSII) polypeptides has been controversal. While we had concluded that the synthesis of the psbC gene product (P6) was specifically deficient in this mutant, another laboratory has found that the synthesis of the psbA gene product, the herbicide-binding protein D1, was primarily affected. These conflicting results were re-analyzed through genetic and biochemical characterization of the different strains used by the two laboratories in question. While the strain used in our laboratory carries the single F34 mutation responsible for the deficiency of P6, the other strain contains three nuclear mutations: the original F34 mutation, a suppressor mutation of F34 and a second PSII mutation, F35. Mutation F35 does not affect P6 synthesis but is responsible for the deficiency in the synthesis of the herbicide-binding protein D1. Furthermore, since both F34 and F35 mutant strains accumulate wild-type levels of psbC and psbA transcripts, we show that these nuclear mutations affect nuclear genes whose products are involved in the expression of psbC or psbA at a post-transcriptional level.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5028
    Keywords: Chlamydomonas reinhardtii ; chloroplast gene expression ; insertional mutagenesis ; cytochrome b6f complex ; nuclear-encoded factors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The random integration of transforming DNA into the nuclear genome of Chlamydomonas has been employed as an insertional mutagen to generate a collection of photosynthetic mutants that display abnormal steady-state fluorescence levels and an acetate-requiring phenotype. Electron paramagnetic resonance spectroscopy was then used to identify those mutants that specifically lack a functional cytochrome b6f complex. Our analysis of RNA and protein synthesis in five of these mutants reveals four separate phenotypes. One mutant fails to accumulate transcript for cytochrome f, whilst a second displays a severely reduced accumulation of the cytochrome b6 transcript. Two other mutants appear to be affected in the insertion of the haem co-factor into cytochrome b6. The fifth mutant displays no detectable defect in the synthesis of any of the known subunits of the complex. Genetic analysis of the mutants demonstrates that in three cases, the mutant phenotype co-segregates with the introduced DNA. For the mutant affected in the accumulation of the cytochrome f transcript, we have used the introduced DNA as a tag to isolate the wild-type version of the affected gene.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-5028
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have examined 78 chloroplast mutants of Chlamydomonas reinhardii lacking photosystem II activity. Most of them are unable to synthesize the 32 Kdalton protein. Analysis of 22 of these mutants reveals that they have deleted both copies of the psbA gene (which codes for the 32 Kdalton protein) in their chloroplast genome. Although these mutants are able to synthesize and to integrate the other photosystem II polypeptides in the thylakoid membranes, they are unable to assemble a stable functional photosystem II complex. The 32 Kprotein appears therefore to play an important role not only in photosystem II function, but also in stabilizing this complex.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 223 (1990), S. 417-425 
    ISSN: 1617-4623
    Keywords: Chloroplast ; Photosystem I ; RNA processing ; Intron
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In Chlamydomonas reinhardtii the three exons of the psaA gene are widely scattered on the chloroplast genome: exons 1 and 2 are in opposite orientations and distant from each other and from exon 3. The mature mRNA, encoding a core polypeptide of photosystem I, is thus probably assembled from separate precursors by splicing in trans. We have isolated and characterized a set of mutants that are deficient in the maturation of psaA mRNA. The mutants belong to 14 nuclear complementation groups and one chloroplast locus that are required for the assembly of psaA mRNA. The chloroplast locus, tscA, is remote from any of the exons and must encode a factor required in trans. The mutants all show one of only three phenotypes that correspond to defects in one or other or both of the joining reactions. These phenotypes, and those of double mutants, are consistent with the existence of two alternative splicing pathways.
    Type of Medium: Electronic Resource
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