No abstract

Genetic modiWcation of nitrogen metabolism via bacterial NADPH-dependent glutamate dehydrogenase (GDH; E.C.4.1.2.1) favorably alters growth and metabolism of C3 plants. The aim of this study was to examine the eVect 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 Wrst 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 speciWc activity produced infertile R0 plants. The highest speciWc activity of GDH from the fertile Z. mays plants was suYcient to alter phenotypes. Plant damage caused by the phosphinothricin in gluphosinate-type herbicides, glutamine synthetase (GS; EC 6.1.3.2) 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 Weld during seasons with signiWcant water deWcits but not over all locations. Water deWcit tolerance under controlled conditions was increased. Crops modiWed with gdhA may have value in semi-arid locations.

No abstract

Parasporal crystals of the recently isolated Bacillus thuringiensis var. tenebrionis are toxic for coleopteran larvae. Unlike those of other strains they are soluble either in aqueous solutions of NaBr at neutral pH or in water after titration to pH values above pH 10.0. The dissolved crystal protein readily forms crystals after removal of the salt or neutralization. The crystal protein was not found to differ much in the amino acid composition from other crystal proteins. The parasporal crystals are composed of subunits of Mr 68 000 which are not linked by disulfide bridges.

This report describes a method for quantifying δ-endotoxin contents in spray-dried preparations ofBacillus thuringiensis strain GC-91. δ-Endotoxin is solubilized in the pro-toxin form and separated from other soluble compounds by ion exchange chromatography. The method does not discriminate between the different δ-endotoxins produced by strain GC-91. It is suitable for quality control, since δ-endotoxin concentrations found in different preparations correlate inversely with the LC 50 in bioassays on artificial diet against freshly hatched larvae ofSpodoptera littoralis. A typical batch of spray-dried material contains 1.22%±0.08% δ-endotoxin. The method is most accurate with preparations containing 0.5 to 2.0% toxin, for which triplicate estimations give standard errors close to±0.2%.