Poster: Metabolic engineering

Abs # 287: Increased glutamine content in leaves of GS1a transgenic poplar significantly enhances transcription of the anthranilate synthase (AS) α -subunit

Presenter:	Man, Hui-minh , hman@andromeda.rutgers.edu
Authors	Man, Hui-minh  (A)   Minocha, Rakesh  (B)   Kirby, Edward  (A)
Affiliations:	(A): Rutgers University (B): USDA Forest Service, NERS

Transformed hybrid poplar (Populus tremula L. X P. alba L., clone--INRA 7171-B4) expressing the pine cytosolic glutamine synthetase gene (GS1a) show significant improvement in plant growth, enhanced GS activity, and increased levels of free glutamine, compared with non-transformed controls (Gallardo et al, 1999; Fu et al. 2003). Improved growth of transgenic lines prompts us to examine possible roles of glutamine in overall nitrogen metabolism and in the regulation of plant growth. The initial reaction in the pathway leading to production of indole-3-acetic acid (IAA) in plants is the reaction of chorismate and glutamine to produce anthranilate, catalyzed by the enzyme anthranilate synthase (AS). Using RT-PCR and real-time PCR, we have shown that transcription of the α-subunit of AS is enhanced in leaves of GS1a transgenic lines of poplar. Exogenous feeding of amino acids (30 mM) to detached tobacco leaves showed that of the amino acids tested, only glutamine and γ-amino butyric acid (GABA) significantly enhanced transcription of the AS α-subunit. The possible role of glutamate/glutamine ratio in moderating nitrogen/carbon metabolism and the possible function of glutamine in promoting plant growth will be discussed.