|Samac, Deborah - Debby|
Submitted to: Nitrogen Fixation International Congress
Publication Type: Abstract Only
Publication Acceptance Date: 6/30/1997
Publication Date: N/A
Technical Abstract: Two approaches were used to evaluate the role of phosphoenolpyruvate carboxylase (PEPC, EC 22.214.171.124) in N2 fixation and N assimilation of alfalfa. Transgenic plants were generated containing an antisense cDNA construct of nodule PEPC driven by the nodule enhanced AAT-2 promoter. Compared to the transformed controls, 10 antisense PEPC plants show a clear rreduction in PEPC enzyme activity and protein (Western blot). This reduction ranged from 35 to 90% and was accompanied by a comparable decrease in PEPC mRNA. Individual antisense PEPC plants when clonally propagated were altered in viability. The second approach involved treating nodules with the PEPC competitive inhibitor, 3,3-dichloro-2- dihydroxyphosphinoylmethyl-2-propenoate (DCDP). In vitro DCDP inhibits PEPC but not other enzymes of N metabolism. Results from experiments comparing the impact of DCDP treatment versus antisense PEPC inhibition on N2 fixation, N assimilation, nodule CO2 fixation, amino acids, and organic acid labeling will be presented. Funding source Deutsche Akadamie der Naturforscher Lepoldina (J.S.) and NSF/IBN: 9206890.