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Has files: YesSubject: search.filters.subject.glutamate decarboxylase

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    PublicationOpen Access
    Calcium/calmodulin activation of two divergent glutamate decarboxylases from tobacco
    (Oxford University Press, 2003-08-01) Yevtushenko, D. P; McLean, M. D; Peiris, S; Cauwenberghe, O. R. V; Shelp, B. J
    Glutamate decarboxylase (GAD, EC 4.1.1.15) catalyses the α‐decarboxylation of glutamate to produce γ‐aminobutyrate (GABA). The nucleotide sequences of two divergent GADs (designated GAD1 and GAD3) were isolated from a Nicotianatabacum L. cv. Samsun NN leaf cDNA library. Open reading frames indicated that GAD1 encodes a polypeptide of 496 amino acids and has greater than 99% identity with known tobacco GADs, whereas GAD3 encodes a polypeptide of 491 amino acids and has about 14% divergence from known tobacco GADs. Genomic DNA analysis suggested that there are at least four tobacco GAD genes, existing in pairs of highly identical genes. An in vitro assay at pH 7.3 revealed that activities of the recombinant proteins, after isolation from Escherichia coli and partial purification by nickel‐affinity chromatography, are 57–133 times the control levels in the presence of 0.5 mM calcium and 0.2 µM bovine calmodulin.
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    PublicationOpen Access
    Overexpression of glutamate decarboxylase in transgenic tobacco plants deters feeding by phytophagous insect larvae
    (Kluwer Academic Publishers-Plenum Publishers, 2003-09) MacGregor, K. B; Shelp, B. J; Peiris, S; Bown, A. W
    Gamma-aminobutyrate (GABA) is a ubiquitous four-carbon, nonprotein amino acid synthesized by glutamate decarboxylase. Previous research suggests that the endogenous synthesis of GABA, a naturally occurring inhibitory neurotransmitter at neuromuscular junctions, serves as a plant resistance mechanism against invertebrate pests. In this study, two homozygous transgenic tobacco lines constitutively overexpressing a single copy of a full-length chimeric glutamate decarboxylase cDNA and possessing enhanced capacity for GABA accumulation (GAD plants), a homozygous transgenic line lacking the gene insert, and wild-type tobacco were employed. Tobacco budworm larvae were presented with plantattached wild type and transgenic leaves for 4 hr in a feeding preference study. Larvae consumed six to twelve times more leaf tissue from wild-type plants than from GAD plants. These results suggest that leaf GABA accumulation, which is known to occur in response to insect larval walking and feeding, represents a rapidly deployed localresistance mechanism.