| | 1 | Author
| BenjaminF. Matthews, JackM W Idholm | Requires cookie* | | | Title
| Expression of Aspartokinase, Dihydrodipicolinic Acid Synthase and Homoserine Dehydrogenase During Growth of Carrot Cell Suspension Cultures on Lysine-and Threonine-Supplemented Media  | | | | Abstract
| Reduction in the amounts o f activity o f the first enzyme, aspartokinase (EC 2.7.2.4) and two branch-point enzymes, dihydrodipicolinic acid synthase (EC 4.2.1.52) and homoserine dehydrogen ase (EC 1.1.1.3), located in the pathway for the synthesis o f aspartate-fam ily am ino acids, oc curred when cell suspension cultures of Daucus carota L. var. Danvers were grown in media contain ing 2 m M threonine or 2 m M lysine, endproducts of the pathway. Activity o f the lysine-sensitive form of aspartokinase was decreased when cells were grown in medium containing lysine and the ac tivity of the threonine-sensitive form was decreased when cells were grown in m edium containing threonine. Activity o f the branch-point enzyme leading to threonine synthesis, hom oserine dehy drogenase, was decreased up to 70% in specific activity (units/m g protein) and relative activity (units/g fresh weight) when cells were grown in m edia containing lysine or threonine. Threonine had no effect on the relative activity of dihydrodipicolinic acid synthase, but decreased its specific activity. Lysine decreased the relative activity of the synthase by up to 40%, but had little effect on its specific activity. The decreased activities o f the enzymes were apparently not due to binding of the inhibitory amino acids to the enzymes since homogenization of cells in buffer with 2 m M lysi ne and threonine did not decrease the m easurable enzyme activities. These and other results pres ented suggest that both forms of the aspartokinase activity and homoserine dehydrogenase activi ty can be altered by supplementing the growth medium with lysine or threonine. | | | |
Reference
| Z. Naturforsch. 34c, 1177—1185 (1979); received June 18 1979 | | | |
Published
| 1979 | | | |
Keywords
| Daucus carota, Suspension Cultures, Amino Acids, Enzyme Regulation | | | |
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| default:Reihe_C/34/ZNC-1979-34c-1177.pdf | | | | Identifier
| ZNC-1979-34c-1177 | | | | Volume
| 34 | |
| 3 | Author
| Jonathan Gressel | Requires cookie* | | | Title
| A Review of the Place of in vitro Cell Culture Systems in Studies of Action, Metabolism and Resistance of Biocides Affecting Photosynthesis | | | | Abstract
| The hom ogeneity, density and axenic nature of cell culture system s have made them an am e nable tool for studying many aspects of biocide research; screening, m etabolism , m ode of action and resistance. Cell cultures are "m ulti-hom ogeneous" and each hom ogeneous state may be analog ous to different plant parts. Cultures can be hom ogeneously green, hom ogeneously w hite in either a hom ogeneously exponential or stationary phase of growth. Exam ples are be presented showing why no sin gle hom ogeneous state should be envisaged to be analogous to a whole plant in biocide studies. Because of the possibility of more uniform herbicide application, culture systems have a use in isolatin g resistant crop strains, at higher selection pressures and much higher "p lan t" densities than is possib le in the field, with recent successes. Protoplast fusion techniques may allow the transfer of gen etic resistance between related but genetically incom patible crop species. | | | |
Reference
| Z. Naturforsch. 34c, 905—913 (1979); received M ay 24 1979 | | | |
Published
| 1979 | | | |
Keywords
| Callus Cultures, Suspension Cultures, H erbicide Action, H erbicide M etabolism, H erbicide R esistance | | | |
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| default:Reihe_C/34/ZNC-1979-34c-0905.pdf | | | | Identifier
| ZNC-1979-34c-0905 | | | | Volume
| 34 | |
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