Abstract Detail

Biochemistry, metabolism, carbon flux

Kambhampati, Shrikaar [1], Marsolais, Frederic [2].

Role of a class I glutamine amidotransferase (GAT1_2.1) in maintaining C/N balance in roots of Arabidopsis thaliana.

Balance between carbon and nitrogen metabolism is a requirement for the sustained growth of organisms. In plant leaves, this balance is achieved by inter-relationships between the processes of photosynthesis, respiration and amino acid metabolism in a photoperiod dependent manner. The GS/GOGAT cycle is one such mechanism and is highly elucidated in plants to serve as a cross-road between C and N metabolism. Non-photosynthetic tissues (e.g., roots, germinating seeds), however, lack a sufficient supply of carbon skeletons under high N conditions and hence may resort to other mechanisms, along with GS/GOGAT cycle, to achieve the aforementioned C/N balance. Our understanding of the pathways involved in this major aspect of plant regulation, to date, is limited. The current research proposes the potential role of an enzyme, GAT1_2.1, in hydrolyzing excess glutamine to Glu which may serve as carbon skeletons for channeling C to the TCA cycle, under high N conditions, using Arabidopsis as a model. GAT1_2.1, a gene coding for a class I glutamine amidotrasferase of unknown substrate specificity, was shown to be highly responsive to N status and has a root specific expression in Arabidopsis. The protein is mitochondrial localized and the gene is found to be highly co-expressed with Glutamate Dehydrogenase 2 (GDH2). Preliminary metabolite profiling data, using gat1_2.1 mutant of Arabidopsis, suggest that in the absence of GAT1_2.1, GABA shunt pathway is activated to replenish the depleted levels of Glu. This Glu may then be deaminated to 2-oxoglutarate by GDH2 and channelled into the TCA cycle thus providing a cross-road between C and N metabolism in root mitochondria.

1 - Western University, Biology, 1151 Richmond street, London, ON, N6A 5B7, Canada
2 - Southern Crop Protection and Food Research Center, 1391, Sandford street, London, ON, N5V 4T3, Canada

Keywords:
Arabidopsis
Roots
C/N balance
Mass Spectrometry
Glutamine amidotransferase
Carbon cycle
Nitrogen Assimilation.

Presentation Type: Oral Paper:Papers for Topics
Session: 27
Location: Hall A/The Shaw Conference Centre
Date: Tuesday, July 28th, 2015
Time: 8:30 AM
Number: 27003
Abstract ID:1027
Candidate for Awards:CSPB President's Award for Best Student Presentation,CSPB Travel Bursary