Poster: Metabolic Engineering

Abs # 996: Increased glutamine content in leaves of pine-GS1a transgenic poplar significantly enhances transcription of anthranilate synthase (AS) a-subunit

Presenter:	Man, Huimin , hman@andromeda.rutgers.edu
Authors	Man, Huimin  (A)   Kirby, Edward G (A)
Affiliations:	(A): Rutgers University

Transformed hybrid poplar (Populus tremula L.XP.alba L.,clone--INRA 7171-B4) lines expressing the pine cytosolic glutamine synthetase (GS1a) show significant improvement in plant growth, enhanced GS activity,and increased levels of free Glutamine (Gln), compared with controls (Gallardo et al,1999;Fu et al,2003). Improved growth of transgenic lines prompts us to examine possible roles of Gln 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 reaction of Gln and Chorismate to produce anthranilate, catalyzed by the enzyme anthranilate synthase (AS).Using RT-PCR,we have shown that transcription of the a-subunit of AS is enhanced in leaves of GS1a transgenic lines of poplar. Exogenous feeding of Gln to detached tobacco leaves showed that 30 mM Gln alone significantly enhanced the transcription of the AS a-subunit. This finding adds further evidence to the significance of Gln involved in: a) down-regulation of expression of high-affinity nitrate transporters (Nrt2.1/2.2)and the high-affinity ammonium transporter (AMT1.1)(Glass et al.,2002), b)acting as signals of internal N status (Coruzzi and Bush,2001) in plant, c) the reaction of Gln with Chorismate leading to the production of IAA, a possible central point at which products of nitrogen metabolism (Gln)and carbon metabolism (Chorismate) meet, leading to the regulation of growth and development of plant.