Transgenic Approaches to Engineer Nitrogen Metabolism

Cánovas, Francisco M.; Gallardo, Fernando; Jing, Zhong; Pascual, María Belén

doi:10.1007/3-540-32199-3_8

Cited by 5 publications

(6 citation statements)

References 80 publications

(88 reference statements)

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“…These findings suggest that the higher level of expression of these two genes could account for the increased levels of phenylalanine in the PpDof5 transgenics that are required for vascular development. Similar results have been described in other plants overexpressing GS genes [11,13,59]. …”

Section: Discussionsupporting

confidence: 89%

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Overexpression of a pine Dof transcription factor in hybrid poplars: A comparative study in trees growing under controlled and natural conditions

et al. 2017

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In this work, the role of the pine transcriptional regulator Dof 5 in carbon and nitrogen metabolism has been examined in poplar trees. The overexpression of the gene and potential effects on growth and biomass production were compared between trees growing in a growth chamber under controlled conditions and trees growing in a field trial during two growth seasons. Ten-week-old transgenic poplars exhibited higher growth than untransformed controls and exhibited enhanced capacity for inorganic nitrogen uptake in the form of nitrate. Furthermore, the transgenic trees accumulated significantly more carbohydrates such as glucose, fructose, sucrose and starch. Lignin content increased in the basal part of the stem likely due to the thicker stem of the transformed plants. The enhanced levels of lignin were correlated with higher expression of the PAL1 and GS1.3 genes, which encode key enzymes involved in the phenylalanine deamination required for lignin biosynthesis. However, the results in the field trial experiment diverged from those observed in the chamber system. The lines overexpressing PpDof5 showed attenuated growth during the two growing seasons and no modification of carbon or nitrogen metabolism. These results were not associated with a decrease in the expression of the transgene, but they can be ascribed to the nitrogen available in the field soil compared to that available for growth under controlled conditions. This work highlights the paramount importance of testing transgenic lines in field trials.

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Section: Discussionsupporting

confidence: 89%

“…Previous results of our research group have shown that manipulation of the structural and regulatory genes involved in nitrogen metabolism may be a valid approach to increasing biomass production in hybrid poplars ( Populus tremula x P . alba ) and to producing wood with improved pulping attributes [7, 10, 11, 12, 13, 14]. …”

Section: Introductionmentioning

confidence: 99%

Overexpression of a pine Dof transcription factor in hybrid poplars: A comparative study in trees growing under controlled and natural conditions

et al. 2017

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“…Other transcription factors overexpressed in the GS transgenics under high N are NAC‐ (Li et al ., ,b; Zhao et al ., ) and MYB ‐related proteins involved in wood formation in Populus (McCarthy et al ., ; Wang et al ., ; Zhong et al ., ). WRKY proteins implicated in abiotic stress responses (He et al ., ) showed similar profiles, and all these results are consistent with the observed tolerance of GS transgenics to different types of stress (Cánovas et al ., ). Overall, transcription factors were up‐regulated in transgenic plants, particularly at high nitrate levels.…”

Section: Discussionmentioning

confidence: 97%

“…Previous analyses of GS1a transgenic poplars also observed reduced free ammonium amounts and increased glutamine levels in response to nitrate (Man et al ., ). We hypothesized that increased availability of organic nitrogen in the form of glutamine confers metabolic advantages to transgenic plants, resulting in improved growth and biomass (Cánovas et al ., ). Furthermore, it has been suggested that overexpression of cytosolic GS results in enhanced primary assimilation of ammonium and reassimilation of N released in photorespiration, protein remobilization and lignin biosynthesis (Cánovas et al ., ; Man et al ., ; Oliveira et al ., ).…”

Section: Discussionmentioning

confidence: 99%

Poplar trees for phytoremediation of high levels of nitrate and applications in bioenergy

Castro-Rodríguez

García‐Gutiérrez

Canales

et al. 2015

Plant Biotechnology Journal

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SummaryThe utilization of high amounts of nitrate fertilizers for crop yield leads to nitrate pollution of ground and surface waters. In this study, we report the assimilation and utilization of nitrate luxuriant levels, 20 times more than the highest N fertilizer application in Europe, by transgenic poplars overexpressing a cytosolic glutamine synthetase (GS1). In comparison with the wild-type controls, transgenic plants grown under high N levels exhibited increased biomass (171.6%) and accumulated higher levels of proteins, chlorophylls and total sugars such as glucose, fructose and sucrose. These plants also exhibited greater nitrogen-use efficiency particularly in young leaves, suggesting that they are able to translocate most of the resources to the above-ground part of the plant to produce biomass. The transgenic poplar transcriptome was greatly affected in response to N availability with 1237 genes differentially regulated in high N, while only 632 genes were differentially expressed in untransformed plants. Many of these genes are essential in the adaptation and response against N excess and include those involved in photosynthesis, cell wall formation and phenylpropanoid biosynthesis. Cellulose production in the transgenic plants was fivefold higher than in control plants, indicating that transgenic poplars represent a potential feedstock for applications in bioenergy. In conclusion, our results show that GS transgenic poplars can be used not only for improving growth and biomass production but also as an important resource for potential phytoremediation of nitrate pollution.

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“…This proposal is supported by the increase in growth observed in transgenic poplars overexpressing constitutively a pine GS gene [ 35 ]. Furthermore, enhanced GS expression in poplar resulted in an enhanced efficiency in nitrogen assimilation and stress tolerance [ 36 , 37 ]. All these data indicate that increased levels of GS confer selective metabolic advantages in poplar trees.…”

Section: Discussionmentioning

confidence: 99%

Redundancy and metabolic function of the glutamine synthetase gene family in poplar

et al. 2015

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BackgroundGlutamine synthetase (GS; EC: 6.3.1.2, L-glutamate: ammonia ligase ADP-forming) is a key enzyme in ammonium assimilation and metabolism in higher plants. In poplar, the GS family is organized in 4 groups of duplicated genes, 3 of which code for cytosolic GS isoforms (GS1.1, GS1.2 and GS1.3) and one group that codes for the choroplastic GS isoform (GS2). Our previous work suggested that GS duplicates may have been retained to increase the amount of enzyme in a particular cell type.ResultsThe current study was conducted to test this hypothesis by developing a more comprehensive understanding of the molecular and biochemical characteristics of the poplar GS isoenzymes and by determinating their kinetic parameters. To obtain further insights into the function of the poplar GS genes, in situ hybridization and laser capture microdissections were conducted in different tissues, and the precise GS gene spatial expression patterns were determined in specific cell/tissue types of the leaves, stems and roots. The molecular and functional analysis of the poplar GS family and the precise localization of the corresponding mRNA in different cell types strongly suggest that the GS isoforms play non-redundant roles in poplar tree biology. Furthermore, our results support the proposal that a function of the duplicated genes in specific cell/tissue types is to increase the abundance of the enzymes.ConclusionTaken together, our results reveal that there is no redundancy in the poplar GS family at the whole plant level but it exists in specific cell types where the two duplicated genes are expressed and their gene expression products have similar metabolic roles. Gene redundancy may contribute to the homeostasis of nitrogen metabolism in functions associated with changes in environmental conditions and developmental stages.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-014-0365-5) contains supplementary material, which is available to authorized users.

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Transgenic Approaches to Engineer Nitrogen Metabolism

Cited by 5 publications

References 80 publications

Overexpression of a pine Dof transcription factor in hybrid poplars: A comparative study in trees growing under controlled and natural conditions

Overexpression of a pine Dof transcription factor in hybrid poplars: A comparative study in trees growing under controlled and natural conditions

Poplar trees for phytoremediation of high levels of nitrate and applications in bioenergy

Redundancy and metabolic function of the glutamine synthetase gene family in poplar

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