Characterization of transgenic poplar with ectopic expression of pine cytosolic glutamine synthetase under conditions of varying nitrogen availability

• Published in: The New phytologist Vol. 167; no. 1; pp. 31 - 39
• Main Authors: Man, H, Boriel, R, El-Khatib, R, Kirby, E.G
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science 01.07.2005; Blackwell Science Ltd; Blackwell
• Subjects: Agronomy. Soil science and plant productions; Amino acids; Amino Acids - metabolism; ammonia; ammonia assimilation; assimilation (physiology); Biological and medical sciences; Economic plant physiology; enzyme activity; forest trees; free amino acids; Fructification, ripening. Postharvest physiology; Fundamental and applied biological sciences. Psychology; gene expression regulation; glutamate-ammonia ligase; Glutamate-Ammonia Ligase - genetics; Glutamate-Ammonia Ligase - metabolism; glutamine; glutamine synthetase (GS); Growth and development; hybrids; Leaves; Metabolism; Nitrates; Nitrogen; Nitrogen - metabolism; nitrogen assimilation; nutrient solutions; Nutrient use efficiency; Pine trees; Pinus - enzymology; Pinus sylvestris; Plant growth; Plant Leaves - metabolism; plant nutrition; Plant physiology and development; plant proteins; Plants; Plants, Genetically Modified; Populus (poplar); Populus - genetics; Populus - metabolism; Populus alba; Populus tremula; Quaternary ammonium compounds; transgenes; Transgenic plants; transgenic poplar; Assimilation; Carbon-nitrogen ligases; Enzyme; Growth; Metabolism; nitrogen assimilation; Salicaceae; ammonia assimilation; glutamine synthetase (GS); Ammonia; transgenic poplar; Ligases; Dicotyledones; Aminoacid; Angiospermae; Hardwood forest tree; Spermatophyta; Transgenic plant; Populus (poplar); Populus; Glutamate-ammonia ligase
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/j.1469-8137.2005.01461.x

$\bullet$ The present study addresses the hypothesis that enhanced expression of glutamine synthetase (GS) in transgenic poplar, characterized by the ectopic expression of pine cytosolic GS, results in an enhanced efficiency of nitrogen (N) assimilation and enhanced growth. $\bullet$ Transgenic and control poplar were supplied with low and high N levels and the role of ectopic expression of the pine GS in growth and N assimilation was assessed by using amino acid analysis, 15N enrichment, biochemical analyses, and growth measurements. $\bullet$ While leaves of transgenic poplar contained 85% less (P < 0.01) free ammonium than leaves of nontransgenic control plants, leaves of transgenics showed increases in the levels of free glutamine and total free amino acids. Transgenic poplar lines also displayed significant increases in growth parameters when compared with controls grown under both low (0.3 mM) and high (10 mM) nitrate conditions. Furthermore, $^{15}N-enrichment$ experiments showed that 27% more (P < 0.05) 15N was incorporated into structural compounds in transgenic lines than in nontransgenic controls. $\bullet$ Using the methods described here, we present direct evidence for increased N assimilation efficiency and growth in GS transgenic lines.