Improved drought tolerance of transgenic Zea mays plants that express the glutamate dehydrogenase gene (gdhA) of E. coli
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Genetic modification of nitrogen metabolism via bacterial NADPH- dependent glutamate dehydrogenase (GDH; E.C.18.104.22.168) favorably alters growth and metabolism of C3 plants. The aim of this study was to examine the effect of expression of GDH in the cytoplasmic compartment of Zea mays cells. The gdhA gene from Escherichia coli , that encoded a NADPH-GDH, was ligated to the ubiquitin promoter that incorporated the first intron enhancer and used to transform Z. mays cv. ‘H99’ embryo cultures by biolistics. R0–R3 generations included selfed inbreds, back-crossed inbreds, and hybrids with B73 derivatives. The lines with the highest GDH specific activity produced infertile R0 plants. The highest specific activity of GDH from the fertile Z. mays plants was sufficient to alter phenotypes. Plant damage caused by the phosphinothricin in gluphosinate-type herbicides, glutamine synthetase (GS; EC 22.214.171.124) inhibitors, was less pronounced in Z. mays plants with gdhA pat than in gusA pat plants. Germination and grain biomass production were increased in gdhA transgenic plants in the field during seasons with significant water deficits but not over all locations. Water deficit tolerance under controlled conditions was increased. Crops modified with gdhA may have value in semi-arid locations.
KeywordsAmmonia assimilation Glutamate dehydrogenase Transgenic plants Phosphinothricin Gluphosinate
Plant materials were developed with a grant from the Herman Frasch foundation and the Illinois Maize Marketing Board. Analyses were supported by grants from the Illinois Missouri Biotechnology Alliance and the Illinois Council for Food and Agricultural Research. We thank P. Bullock at Garst Inc., Highway 210 W, PO Box 500, Slater, Iowa 50244.; and D. Hondred, now at Pioneer Hi-Bred International Inc., Trait and Technology Development, 7300 NW 62 nd Ave., PO Box 1004, Johnson, Iowa 50131-1004 for transformation an analysis advice. We thank Dr. J. Preece and Dr. G. Kapusta for advice, E. Cerny and R. Lang for technical assistance.
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