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  • 1
    Electronic Resource
    Electronic Resource
    Light-regulated expression of the nitrate-reductase and nitrite-reductase genes in tomato and in the phytochrome-deficient aurea mutant of tomato (1992)
    Springer
    Planta 188 (1992), S. 39-47 
    Details
    ISSN: 1432-2048
    Keywords: Gene expression ; Lycopersicon ; Mutant (tomato, aurea) ; Nitrate reductase ; Nitrite reductase ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The phytochrome-deficient aurea mutant of tomato (Lycopersicon esculentum (L.) Mill) was used to investigate if phytochrome plays a role in the regulation of nitrate-reductase (NR, EC 1.6.6.1) and nitrite-reductase (NiR, EC 1.7.7.1) gene expression. We show that the expression of the tomato NR and NiR genes is stimulated by light and that this light response is mediated by the photoreceptor phytochrome. The red-light response of the NR and NiR genes was reduced in etiolated aurea seedlings when compared to isogenic wild-type cotyledons. The relative levels of NR mRNA and NiR transcripts and their diurnal fluctuations were identical in mature white-light-grown leaves of the wild-type and of the aurea mutant. The transcript levels for cab and RbcS (genes for the chlorophyll-a/b-binding protein of PSII and the small subunit of the enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase, respectively) in aurea leaves grown in white light were indistinguishable from the respective transcript levels in the leaves of the wildtype grown under the same conditions. Despite a severe reduction in the chlorophyll content, the rate of net CO2 uptake by leaves of the aurea mutant was only slightly reduced when compared to the rate of net photosynthesis of wild-type leaves. This difference in the photosynthetic performances of wild-type and aurea mutant plants disappeared during aging of the plants. The increase in zeaxanthin and the concomitant decrease in violaxanthin in leaves of the aurea mutant compared with the same pigment levels in leaves of the wild-type indicate that the activity of the xanthophyll cycle is increased in aurea leaves as a consequence of the reduced CO2-fixation capacity of the mutant leaves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00198937
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  • 2
    Electronic Resource
    Electronic Resource
    Light-regulated expression of the nitrate-reductase and nitrite-reductase genes in tomato and in the phytochrome-deficientaurea mutant of tomato (1992)
    Springer
    Planta 188 (1992), S. 39-47 
    Details
    ISSN: 1432-2048
    Keywords: Gene expression ; Lycopersicon ; Mutant (tomato,aurea) ; Nitrate reductase ; Nitrite reductase ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The phytochrome-deficientaurea mutant of tomato (Lycopersicon esculentum (L.) Mill) was used to investigate if phytochrome plays a role in the regulation of nitrate-reductase (NR, EC 1.6.6.1) and nitrite-reductase (NiR, EC 1.7.7.1) gene expression. We show that the expression of the tomato NR and NiR genes is stimulated by light and that this light response is mediated by the photoreceptor phytochrome. The red-light response of the NR and NiR genes was reduced in etiolatedaurea seedlings when compared to isogenic wild-type cotyledons. The relative levels of NR mRNA and NiR transcripts and their diurnal fluctuations were identical in mature white-light-grown leaves of the wild-type and of theaurea mutant. The transcript levels forcab andRbcS (genes for the chlorophyll-a/b-binding protein of PSII and the small subunit of the enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase, respectively) inaurea leaves grown in white light were indistinguishable from the respective transcript levels in the leaves of the wildtype grown under the same conditions. Despite a severe reduction in the chlorophyll content, the rate of net CO2 uptake by leaves of theaurea mutant was only slightly reduced when compared to the rate of net photosynthesis of wild-type leaves. This difference in the photosynthetic performances of wild-type andaurea mutant plants disappeared during aging of the plants. The increase in zeaxanthin and the concomitant decrease in violaxanthin in leaves of theaurea mutant compared with the same pigment levels in leaves of the wild-type indicate that the activity of the xanthophyll cycle is increased inaurea leaves as a consequence of the reduced CO2-fixation capacity of the mutant leaves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01160710
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  • 3
    Electronic Resource
    Electronic Resource
    Regulation of the subunit composition of tomato plastidic glutamine synthetase by light and the nitrogen source (1996)
    Springer
    Planta 200 (1996), S. 213-220 
    Details
    ISSN: 1432-2048
    Keywords: Gene expression ; Glutamine synthetase ; Nitrogen source ; Phosphinothricin ; Phytochrome ; Solanum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The co-action of light and the N-source in the regulation of the expression of the single-copy gene encoding plastidic glutamine synthetase (GS-2) and of the multigene family encoding cytosolic glutamine synthetase (GS-1) was investigated in the cotyledons of tomato (Lycopersicon esculentum L.). Light, acting at red/far red or at blue regions of the spectrum increased the abundance of the GS-2 gene product and induced a modification of GS-2 subunits, resulting in the appearance of two GS-2 proteins exhibiting different molecular weights. The magnitude of the light stimulation of GS-2 gene expression was independent of the nitrogen source. However, following red- or far-red-light treatment of etiolated tomato cotyledons, two GS-2 proteins were found when nitrate was the N-source, while only one GS-2 protein was present with ammonium as the sole nitrogen source. Thus, light of specific wavelengths and N-substrates seem to act in concert to regulate GS-2 subunit composition. Tomato GS-1 gene expression was unaffected by light. Ammonium provided externally increased the level of the tomato GS-1 protein. Irrespective of the N-source or the light quality, the GS-1 subunits were represented by polypeptides of similar molecular weight in tomato cotyledons. However, phosphinothricin-induced inhibition of GS activity resulted in the appearance of at least one additional GS-1 polypeptide in etiolated or in green tomato cotyledons. In addition, impairment of GS activity in green tomato cotyledons by phosphinothricin was correlated with an increased level of the GS-1 transcript. Taken together, our data suggest a metabolic control of GS-1 gene expression in green tomato cotyledons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00208311
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