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Metabolic profiling reveals altered sugar and secondary metabolism in response to UGPase overexpression in Populus.

Payyavula RS, Tschaplinski TJ, Jawdy SS, Sykes RW, Tuskan GA, Kalluri UC - BMC Plant Biol. (2014)

Bottom Line: Overexpression of the native gene resulted in increased leaf area and leaf-to-shoot biomass ratio but decreased shoot and root growth.While cellulose and lignin levels in the cell walls were not significantly altered, the syringyl-to-guaiacyl ratio was significantly reduced.These results demonstrate that PdUGPase2 plays a key role in the tightly coupled primary and secondary metabolic pathways and perturbation in its function results in pronounced effects on growth and metabolism beyond cell wall biosynthesis of Populus.

View Article: PubMed Central - PubMed

ABSTRACT

Background: UDP-glucose pyrophosphorylase (UGPase) is a sugar-metabolizing enzyme (E.C. 2.7.7.9) that catalyzes a reversible reaction of UDP-glucose and pyrophosphate from glucose-1-phosphate and UTP. UDP-glucose is a key intermediate sugar that is channeled to multiple metabolic pathways. The functional role of UGPase in perennial woody plants is poorly understood.

Results: We characterized the functional role of a UGPase gene in Populus deltoides, PdUGPase2. Overexpression of the native gene resulted in increased leaf area and leaf-to-shoot biomass ratio but decreased shoot and root growth. Metabolomic analyses showed that manipulation of PdUGPase2 results in perturbations in primary, as well as secondary metabolism, resulting in reduced sugar and starch levels and increased phenolics, such as caffeoyl and feruloyl conjugates. While cellulose and lignin levels in the cell walls were not significantly altered, the syringyl-to-guaiacyl ratio was significantly reduced.

Conclusions: These results demonstrate that PdUGPase2 plays a key role in the tightly coupled primary and secondary metabolic pathways and perturbation in its function results in pronounced effects on growth and metabolism beyond cell wall biosynthesis of Populus.

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Dry weight of different plant parts in control and twoUGPase2transgenic lines. Dry weights corresponding to leaf (A), stem (B), and root (D) and the ratio of leaf to stem dry weight (C) are presented. Data represent means ± SE (n = 3). *indicates statistically significant, p ≤ 0.05 based on Student’s t-tests.
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Fig4: Dry weight of different plant parts in control and twoUGPase2transgenic lines. Dry weights corresponding to leaf (A), stem (B), and root (D) and the ratio of leaf to stem dry weight (C) are presented. Data represent means ± SE (n = 3). *indicates statistically significant, p ≤ 0.05 based on Student’s t-tests.

Mentions: Transgenic Populus deltoides plants overexpressing the PdUGPase2 gene (Potri.017G144700) under the control of a constitutive Polyubiquitin 3 (AtUBQ3, Accession L05363) promoter were maintained and characterized under greenhouse conditions. In an initial transgenic phenotyping study, all PdUGPase2 overexpression lines were found to be consistently shorter in height (20 to 50%) with thinner stems (37 to 47%) compared to control plants (Additional file 3). Assessment of an independently grown second set of transgenic plants confirmed that plant height and stem diameter were consistently smaller relative to controls (Figure 3A and B). Conversely, leaf area (35 to 55%) and petiole length (45 to 55%) were significantly greater in transgenics (Figure 3C and D), though total leaf dry weight was reduced as a result of fewer leaves (Figure 4A). Additionally, reduced plant height and stem diameter resulted in a significant reduction in stem dry weight (Figure 4B). When compared to controls, leaf-to-stem biomass ratio doubled (Figure 4C), whereas root weight and root surface area were reduced (50%) in transgenic plants (Figures 3E, F and 4D). We quantified UGPase2 transcript levels in mature leaf petioles of three selected lines and found that PdUGPase2 expression increased 2-fold (Additional file 4). Our results suggest that modest changes in native UGPase2 levels can have pronounced morphological effects on plant phenotype in woody perennials such as Populus.Figure 3


Metabolic profiling reveals altered sugar and secondary metabolism in response to UGPase overexpression in Populus.

Payyavula RS, Tschaplinski TJ, Jawdy SS, Sykes RW, Tuskan GA, Kalluri UC - BMC Plant Biol. (2014)

Dry weight of different plant parts in control and twoUGPase2transgenic lines. Dry weights corresponding to leaf (A), stem (B), and root (D) and the ratio of leaf to stem dry weight (C) are presented. Data represent means ± SE (n = 3). *indicates statistically significant, p ≤ 0.05 based on Student’s t-tests.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4197241&req=5

Fig4: Dry weight of different plant parts in control and twoUGPase2transgenic lines. Dry weights corresponding to leaf (A), stem (B), and root (D) and the ratio of leaf to stem dry weight (C) are presented. Data represent means ± SE (n = 3). *indicates statistically significant, p ≤ 0.05 based on Student’s t-tests.
Mentions: Transgenic Populus deltoides plants overexpressing the PdUGPase2 gene (Potri.017G144700) under the control of a constitutive Polyubiquitin 3 (AtUBQ3, Accession L05363) promoter were maintained and characterized under greenhouse conditions. In an initial transgenic phenotyping study, all PdUGPase2 overexpression lines were found to be consistently shorter in height (20 to 50%) with thinner stems (37 to 47%) compared to control plants (Additional file 3). Assessment of an independently grown second set of transgenic plants confirmed that plant height and stem diameter were consistently smaller relative to controls (Figure 3A and B). Conversely, leaf area (35 to 55%) and petiole length (45 to 55%) were significantly greater in transgenics (Figure 3C and D), though total leaf dry weight was reduced as a result of fewer leaves (Figure 4A). Additionally, reduced plant height and stem diameter resulted in a significant reduction in stem dry weight (Figure 4B). When compared to controls, leaf-to-stem biomass ratio doubled (Figure 4C), whereas root weight and root surface area were reduced (50%) in transgenic plants (Figures 3E, F and 4D). We quantified UGPase2 transcript levels in mature leaf petioles of three selected lines and found that PdUGPase2 expression increased 2-fold (Additional file 4). Our results suggest that modest changes in native UGPase2 levels can have pronounced morphological effects on plant phenotype in woody perennials such as Populus.Figure 3

Bottom Line: Overexpression of the native gene resulted in increased leaf area and leaf-to-shoot biomass ratio but decreased shoot and root growth.While cellulose and lignin levels in the cell walls were not significantly altered, the syringyl-to-guaiacyl ratio was significantly reduced.These results demonstrate that PdUGPase2 plays a key role in the tightly coupled primary and secondary metabolic pathways and perturbation in its function results in pronounced effects on growth and metabolism beyond cell wall biosynthesis of Populus.

View Article: PubMed Central - PubMed

ABSTRACT

Background: UDP-glucose pyrophosphorylase (UGPase) is a sugar-metabolizing enzyme (E.C. 2.7.7.9) that catalyzes a reversible reaction of UDP-glucose and pyrophosphate from glucose-1-phosphate and UTP. UDP-glucose is a key intermediate sugar that is channeled to multiple metabolic pathways. The functional role of UGPase in perennial woody plants is poorly understood.

Results: We characterized the functional role of a UGPase gene in Populus deltoides, PdUGPase2. Overexpression of the native gene resulted in increased leaf area and leaf-to-shoot biomass ratio but decreased shoot and root growth. Metabolomic analyses showed that manipulation of PdUGPase2 results in perturbations in primary, as well as secondary metabolism, resulting in reduced sugar and starch levels and increased phenolics, such as caffeoyl and feruloyl conjugates. While cellulose and lignin levels in the cell walls were not significantly altered, the syringyl-to-guaiacyl ratio was significantly reduced.

Conclusions: These results demonstrate that PdUGPase2 plays a key role in the tightly coupled primary and secondary metabolic pathways and perturbation in its function results in pronounced effects on growth and metabolism beyond cell wall biosynthesis of Populus.

Show MeSH