Al-Quraan, Nisreen , Locy, Robert , Braam, Janet , Singh, Narendra .
Changes in GABA shunt metabolites in calmodulin mutants of Arabidopsis thaliana under abiotic stresses.
Ca2+/calmodulin (CAM) activate plant glutamate decarboxylases (GAD) resulting in the synthesis of GABA. During environmental stresses glutamate (Glu), GABA, and alanine (Ala) all accumulate. Changes in these 3 amino acids were investigated in roots and shoots of 7 cam mutants and in wild-type Arabidopsis given cold, salinity, osmotic, UV, and oxidative stresses. In unstressed control roots, Glu, GABA, and Ala levels were relatively unchanged in all of the cam mutants compared to wild type while in shoots, Glu and Ala levels increased in cam1, 4, 5, 6, & 7 plants. Unstressed shoot GABA levels were higher in cam2, 3, 6, & 7 mutants and lower than wild type levels in cam1, 4, & 5 plants. For all stresses, Glu, GABA and Ala levels increased with time or intensity of the stress. Glu accumulation was higher in roots than in shoots. In some cam mutant/stress combinations Glu increased above control levels, but there was no consistent cam mutant associated with this observation. In general, GABA levels increased by approximately the same fold as Glu, but the GABA levels achieved in maximal treatments were typically 200 to 500-fold lower than for Glu. In some cam mutant/stress combinations GABA levels fell as expected, but surprisingly in other treatment combinations GABA levels increased. The tissue levels of Ala accumulated were in general 1/5 the concentrations of Glu and much higher than the levels of GABA. Taken together the above data suggest that no single cam mutant is specifically associated with GAD in root or shoot tissue, and the effects of CAM paralogs on GABA shunt metabolism are more complex than simply the interaction with GAD. These preliminary mutant characterizations await further experiments to confirm causality between phenotype and gene function.
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More Detailed Abstract
1 - Auburn University, Department of Biological Sciences, 101 Life Sciences Building, Auburn, AL, 36849, USA
2 - Rice University, Department of Biochemistry and Cell Biology, MS-140, 6100 Main Street, Houston, Texas, 77251, USA
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM