Expression of a conifer glutamine synthetase gene in transgenic poplar

Citation
F. Gallardo et al., Expression of a conifer glutamine synthetase gene in transgenic poplar, PLANTA, 210(1), 1999, pp. 19-26
Citations number
38
Categorie Soggetti
Plant Sciences","Animal & Plant Sciences
Journal title
PLANTA
ISSN journal
00320935 → ACNP
Volume
210
Issue
1
Year of publication
1999
Pages
19 - 26
Database
ISI
SICI code
0032-0935(199911)210:1<19:EOACGS>2.0.ZU;2-3
Abstract
The assimilation of ammonium into organic nitrogen catalyzed by the enzyme glutamine synthetase (GS; EC 6.3.1.2) has been suggested to be the limiting step for plant nitrogen utilization (H-M. Lam et al. 1995, Plant Cell 7. 8 87-898). We have developed a molecular approach to increase glutamine produ ction in transgenic poplar by the overexpression of a conifer GS gene. A ch imeric construct consisting of the cauliflower mosaic virus 35S promoter fu sed to pine cytosolic GS cDNA and nopaline synthetase polyadenylation regio n was transferred into pBin19 for transformation of a hybrid poplar clone ( INRA 7171-B4, Populus tremula x P. alba) via Agrobacterium tumefaciens. Tra nsformed poplar lines were selected by their ability to grow on selective m edium containing kanamycin. The presence of the introduced gene in the popl ar genome was verified by Southern blotting and polymerase chain reaction a nalysis. Transgene expression was detected in all selected poplar lines at the mRNA level. The detection of the corresponding polypeptide (41 kDa) and increased GS activity in the transgenics suggest that pine transcripts are correctly processed by the angiosperm translational machinery and that GSI subunits are assembled in functional holoenzymes. Expression of the pine G S1 gene in poplar was associated with an increase in the levels of total so luble protein and an increase in chlorophyll content in leaves of transform ed trees. Furthermore, the mean net growth in height of GS-overexpressing c lones was significantly greater than that of non-transformed controls, rang ing from a 76% increase in height at 2 months to a 21.3% increase at 6 mont hs. Our results suggest that the efficiency of nitrogen utilization may be engineered in trees by genetic manipulation of glutamine biosynthesis.