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  • 1
    Electronic Resource
    Electronic Resource
    Blue light adaptation and desensitization of light signal transduction in Neurospora crassa (2001)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 39 (2001), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The ascomycete Neurospora crassa has the capacity of adapting to a given light quantity, leading to transient blue light responses under continuous light conditions. Here, we present an investigation of this photoadaptation phenomenon. We demonstrated previously that two proteins of the Neurospora blue light signal transduction chain, WC1 and WC2, are subject to light-dependent phosphorylation. WC1 was phosphorylated in parallel with the transient increase in transcript levels of light-regulated genes. Using the light-dependent phosphorylation of WC1 as a marker for an active signalling state of WC1, we show that the transiency of Neurospora blue light responses results from desensitization of the photoreceptor and/or the signalling cascade. Furthermore, a Neurospora mutant was characterized that revealed a specific defect in photoadaptation. In this mutant, the transient expression of light-regulated genes under continuous light, the temporary insensitivity after a light pulse and the capability of differentiating between and adapting to low and high light intensities were abolished. The corresponding protein seems to represent a central component of a negative feedback desensitization mechanism. This negative feedback regulation requires continuous and light-dependent protein de novo biosynthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2001.02306.x
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  • 2
    Electronic Resource
    Electronic Resource
    Roles in dimerization and blue light photoresponse of the PAS and LOV domains of Neurospora crassa white collar proteins (1998)
    Oxford BSL : Blackwell Science Ltd, UK
    Molecular microbiology 29 (1998), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The genes coding for white collar-1 and white collar-2 (wc-1 and wc-2 ) have been isolated previously, and their products characterized as Zn-finger transcription factors involved in the control of blue light-induced genes. Here, we show that the PAS dimerization domains present in both proteins enable the WC-1 and WC-2 proteins to dimerize in vitro. Homodimers and heterodimers are formed between the white collar (WC) proteins. A computer analysis of WC-1 reveals a second domain, called LOV, also identified in NPH1, a putative blue light photoreceptor in plants and conserved in redox-sensitive proteins and in the phytochromes. The WC-1 LOV domain does not dimerize with canonical PAS domains, but it is able to self-dimerize. The isolation of three blind wc-1 strains, each with a single amino acid substitution only in the LOV domain, reveals that this region is essential for blue light responses in Neurospora. The demonstration that the WC-1 proteins in these LOV mutants are still able to self-dimerize suggests that this domain plays an additional role, essential in blue light signal transduction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1998.00955.x
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  • 3
    Electronic Resource
    Electronic Resource
    Immunogold localization of phytoene desaturase in higher plant chloroplasts (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 88 (1993), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In situ location of phytoene desaturase, a key enzyme in the carotenoid biosynthesis pathway, has been investigated in chloroplasts from higher plants. For this purpose, an antiserum has been raised against the phytoene desaturase from the cyanobacterium Synechococcus PCC 7942 overexpressed in E. coli. The specifity of this antiserum was demonstrated by inhibition of the enzymatic desaturation reaction in vitro. The antiserum was further purified and immunoabsorbed with E. coli proteins. The resulting IgG-fraction was tested by western blotting against membrane proteins from chloroplasts of tobacco (Nicotiana tabacum L. cv. Samsun) and spinach (Spinacia oleracea L. cv. Atlanta). Apparent molecular masses of immunoreactive proteins were 62 and 64 kDa. A western blot of different membrane fractions of spinach chloroplasts (inner and outer envelopes, and thylakoids) indicated a localization of the phytoene desaturase in thylakoids. A post embedding immunogold microscopy procedure was employed. In these experiments the main labelling (79%) was associated with thylakoid membranes of tobacco chloroplasts. Of the counted colloidal gold particles, 16% were found in the stroma. Only 5% were detected in the envelope membranes. These results give clear evidence that at least the majority of phytoene desaturase molecules is localized within thylakoid membranes of higher plant chloroplasts and that the presence of the enzyme in the envelope is of minor significance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1993.tb05493.x
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  • 4
    Electronic Resource
    Electronic Resource
    Isolation of a carotenoid biosynthesis gene coding for ζ-carotene desaturase from Anabaena PCC 7120 by heterologous complementation (1993)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 106 (1993), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract A screening procedure for carotenoid genes involving heterologous complementation with two different plasmid constructs was developed. The plasmids contained the crtE and crtB genes from Erwinia unredovora together with the phytoene desaturase gene from either Rhodobacter capsulatus or Synechococcus PCC 7942. Transformation in E. coli led to the accumulation of neurosporene and ζ-carotene, respectively. Co-transformation with an Anabaena plasmid library resulted in the isolation of the two plasmids, pZDS1 and pZDS1. Their gene products showed the ability to convert neurosporene and ζ-carotene into lycopene. In contrast, accumulated phytoene could not be converted. We conclude that the cloned gene codes for the carotenoid biosynthesis gene ζ-carotene desaturase (zds).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1993.tb05941.x
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  • 5
    Electronic Resource
    Electronic Resource
    A novel carotenoid biosynthesis gene coding for ζ-carotene desaturase: functional expression, sequence and phylogenetic origin (1994)
    Springer
    Plant molecular biology 24 (1994), S. 369-379 
    Details
    ISSN: 1573-5028
    Keywords: Anabaena PCC 7120 ; carotenoid biosynthesis ; ζ-carotene desaturase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A DNA fragment which has been isolated previously from an Anabaena DNA expression library was subcloned. The corresponding protein was overexpressed in Escherichia coli. The recombinant enzyme was fully active in converting ζ-carotene into lycopene in vitro with neurosporene as an intermediate. A smaller fragment which still contained the active enzyme was sequenced. An open reading frame of 1497 bp was found coding for a protein consisting of 499 amino acids with the calculated molecular weight of 56 740. In a computer search of nucleotide sequences contained in the EMBL nucleotide sequence library, all the best-fitting comparisons were carotenoid desaturases. The highest similarity was found with the crtI phytoene desaturase genes of bacteria and the al-1 gene from Neurospora crassa. A much lower similarity was found with the pds genes coding for phytoene desaturase from cyanobacteria and higher plants. It is shown in protein similarity plots that the amino acid similarity of ζ-carotene desaturase to the latter is mainly limited to the N terminus of the polypeptides. In contrast, the protein similarity plots and a comparison of a conserved region clearly demonstrate that there is a strong relationship between ζ-carotene desaturase and the phytoene desaturases from various bacteria and fungi. Therefore we propose that the ζ-carotene desaturase gene is homologous to the crt I phytoene desaturase genes of bacteria and fungi.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00020174
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