Expression of ferredoxin-dependent glutamate synthase in dark-grown pine seedlings

García‐Gutiérrez, Ángel; Cantón, Francisco R.; Gallardo, Fernando; Sánchez‐Jiménez, Francisca; Cánovas, Francisco M.

doi:10.1007/bf00019183

Cited by 33 publications

(49 citation statements)

References 44 publications

(60 reference statements)

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“…It is surprising that two Fd-GOGAT genes were discovered in Arabidopsis, because single genes for Fd-GOGAT have been reported for plants with much larger genomes. These include maize, tobacco, barley, spinach, and Scots pine (Sakakibara et al, 1991;Zehnacker et al, 1992;Avila et al, 1993;Nalbantoglu et al, 1994;García-Gutiérrez et al, 1995). Because the Arabidopsis GLU2 gene was only discovered after sequencing 13 independent cDNAs (only one of which was GLU2), it is likely that other species contain a second gene for Fd-GOGAT that may have been missed in other cDNA screens because of low expression levels.…”

Section: Discussionmentioning

confidence: 99%

Arabidopsis gls Mutants and Distinct Fd-GOGAT Genes: Implications for Photorespiration and Primary Nitrogen Assimilation

et al. 1998

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Ferredoxin-dependent glutamate synthase (Fd-GOGAT) plays a major role in photorespiration in Arabidopsis, as has been determined by the characterization of mutants deficient in Fd-GOGAT enzyme activity ( gls ). Despite genetic evidence for a single Fd-GOGAT locus and gene, we discovered that Arabidopsis contains two expressed genes for Fd-GOGAT ( GLU1 and GLU2 ). Physical and genetic mapping of the gls1 locus and GLU genes indicates that GLU1 is linked to the gls1 locus, whereas GLU2 maps to a different chromosome. Contrasting patterns of GLU1 and GLU2 expression explain why a mutation in only one of the two genes for Fd-GOGAT leads to a photorespiratory phenotype in the gls1 mutants. GLU1 mRNA was expressed at the highest levels in leaves, and its mRNA levels were specifically induced by light or sucrose. In contrast, GLU2 mRNA was expressed at lower constitutive levels in leaves and preferentially accumulated in roots. Although these results suggest a major role for GLU1 in photorespiration, the sucrose induction of GLU1 mRNA in leaves also suggests a role in primary nitrogen assimilation. This possibility is supported by the finding that chlorophyll levels of a gls mutant are significantly lower than those of the wild type when grown under conditions that suppress photorespiration. Both the mutant analysis and gene regulation studies suggest that GLU1 plays a major role in photorespiration and also plays a role in primary nitrogen assimilation in leaves, whereas the GLU2 gene may play a major role in primary nitrogen assimilation in roots. INTRODUCTIONGlutamate synthase (glutamine-oxoglutarate aminotransferase or GOGAT) is a key enzyme involved in the assimilation of inorganic nitrogen in higher plants ( Lea and Miflin, 1974;Keys et al., 1978;Miflin and Lea, 1980;Stewart et al., 1980). Functioning coordinately with glutamine synthetase (GS; EC 6.3.1.2), the GS/GOGAT pair provides the primary port of entry for nitrogen in whole-plant metabolism. Inorganic nitrogen, in the form of ammonia, is assimilated via this glutamate synthase cycle into the organic nitrogen compounds glutamine and glutamate, which are the nitrogen donors in essentially all biosynthetic reactions involving nitrogen (e.g., amino acids, nucleic acids, and chlorophyll). Primary nitrogen assimilation requires cofactors, reducing equivalents, and carbon skeletons generated during photosynthesis. Thus, in most plants, assimilation of inorganic nitrogen into organic form occurs predominantly in leaf chloroplasts where these components are readily available (Sechley et al., 1992). In plant species that are able to efficiently transport photosynthate to roots, such as maize and temperate legumes, nitrogen assimilation also occurs at high rates in root plastids (Oaks, 1992).In addition to its major role in primary nitrogen assimilation, the GS/GOGAT cycle also plays a crucial role in reassimilating the large amount of ammonia released during photorespiration (Somerville and Ogren, 1980;Kendall et al., 1986). The amount of ammonia released during pho...

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Section: Discussionmentioning

confidence: 99%

Arabidopsis gls Mutants and Distinct Fd-GOGAT Genes: Implications for Photorespiration and Primary Nitrogen Assimilation

et al. 1998

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“…It occurs as several isozymes located in different subcellular compartments, including the cytosol, chloroplast, mitochondria, and peroxisome (Chen and Gadal, 1990b, and refs. therein;Rasmusson and Moller, 1990;Gálvez et al, 1994;Gallardo et al, 1995;Cornu et al, 1996).…”

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confidence: 99%

“…This hypothesis was based on the findings that (a) plant organs exhibit very low NAD ϩ -IDH activity, (b) NADP ϩ -IDH has a higher affinity for substrates, and (c) cytosolic aconitase is present in plants and may produce isocitrate outside of the mitochondria. In angiosperms NADP ϩ -IDH has been studied in a limited number of species, including pea (Omran and Dennis, 1971;Randall and Givan, 1981;Chen et al, 1989a), several members of the Solanaceae (Gálvez et al, 1994;Fieuw et al, 1995;Gallardo et al, 1995), and cucumber (Canino et al, 1996). It occurs as several isozymes located in different subcellular compartments, including the cytosol, chloroplast, mitochondria, and peroxisome (Chen and Gadal, 1990b, and refs.…”

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Purification and Characterization of NADP+-Linked Isocitrate Dehydrogenase from Scots Pine

et al. 1998

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NADP؉ -isocitrate dehydrogenase (NADP ؉ -IDH; EC 1.1.1.42) is involved in the supply of 2-oxoglutarate for ammonia assimilation and glutamate synthesis in higher plants through the glutamine synthetase/glutamate synthase (GS/GOGAT) cycle. Only one NADP ؉ -IDH form of cytosolic localization was detected in green cotyledons of pine (Pinus spp.) seedlings. The pine enzyme was purified and exhibited molecular and kinetic properties similar to those described for NADP ؉ -IDH from angiosperm, with a higher catalytic efficiency (10 5 M ؊1 s ؊1 ) than the deduced efficiencies for GS and GOGAT in higher plants. A polyclonal antiserum was raised against pine NADP ؉ -IDH and used to assess protein expression in the seedlings. Steady-state levels of NADP ؉ -IDH were coordinated with GS during seed germination and were associated with GS/ GOGAT enzymes during chloroplast biogenesis, suggesting that NADP ؉ -IDH is involved in the provision of carbon skeletons for the synthesis of nitrogen-containing molecules. However, a noncoordinated pattern of NADP ؉ -IDH and GS/GOGAT was observed in advanced stages of cotyledon development and in the hypocotyl. A detailed analysis in hypocotyl sections revealed that NADP ؉ -IDH abundance was inversely correlated with the presence of GS, GOGAT, and ribulose-1,5-bisphosphate carboxylase/oxygenase but was associated with the differentiation of the organ. These results cannot be explained by the accepted role of the enzyme in nitrogen assimilation and strongly suggest that NADP ؉ -IDH may have other, as-yet-unknown, biological functions.

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“…Interestingly, the expression of genes involved in the biosynthesis of phenylpropanoids and SAM is strongly correlated with GS1b expression suggesting that GS1b is directly involved in the recycling of ammonium released by PAL and GDC during secondary growth. Fd-GOGAT levels in pine stems are very low suggesting that NADH-GOGAT is more likely involved in the reassimilation of ammonium in lignifying xylem cells [52].…”

Section: Biosynthesis Of Lignins and Lignansmentioning

confidence: 99%

Nitrogen Economy and Nitrogen Environmental Interactions in Conifers

et al. 2016

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Efficient acquisition, assimilation and economy of nitrogen are of special importance in trees that must cope with seasonal periods of growth and dormancy over many years. The ability to accumulate nitrogen reserves and to recycle N determine to a great extent the growth and production of forest biomass. The metabolic relevance of two key amino acids, arginine and phenylalanine, as well as other processes potentially involved in the nitrogen economy of conifers are discussed in the current review. During their long life cycles, conifers not only cope with cyclical annual and long-term changes in the environment but also interact with other organisms such as herbivores and symbionts. The interactions of biotic and abiotic factors with conifer nitrogen metabolism will also be outlined in this review.

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Expression of ferredoxin-dependent glutamate synthase in dark-grown pine seedlings

Cited by 33 publications

References 44 publications

Arabidopsis gls Mutants and Distinct Fd-GOGAT Genes: Implications for Photorespiration and Primary Nitrogen Assimilation

Arabidopsis gls Mutants and Distinct Fd-GOGAT Genes: Implications for Photorespiration and Primary Nitrogen Assimilation

Purification and Characterization of NADP+-Linked Isocitrate Dehydrogenase from Scots Pine

Nitrogen Economy and Nitrogen Environmental Interactions in Conifers

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