De fabricage van methanol uit CO2 en H2

Document(en) uit de collectie Chemische ProcestechnologieDelftChemTechApplied Science

De mogelijkheden van het verbeteren van brouwgerst door recombinant DNA-onderzoek

Het recombinant DNA-onderzoek startte omstreeks 1960. Een belangrijk deel van dit onderzoek op het gebied van gerst wordt uitgevoerd door het Carlsberg Research Center in Kopenhagen. In dit artikel worden diverse mogelijkheden van recombinant DNA-technieken belicht. Aangezien recombinant DNA-technieken waarschijnlijk belangrijk kunnen bijdragen aan een verbetering van de kwaliteit van brouw- en voedergerst, zijn extra research-inspanningen gewenst en noodzakelijk

Plant tumors induced by A. tumefaciens: a genetic approach

It is shown that a large plasmid in A. tumefaciens cells, called the TI-plasmid, besides being essential for oncogenicity also determines: (1) the specificity and the activity of the enzyme-system for octopine or nopaline utilisation; (2) the synthesis of either octopine or nopaline in crown gall cells as well as the morphology of the tumors on Kalanchoë stems. A few A. tumefaciens strains give rise to tumors whose cells do not synthesise octopine or nopaline. This indicates that these compounds themselves are not essential for the tumorous nature of the plant cells. Roots induced by the hairy root disease bacteria of two A. rhizogenes strains tested do not contain nopaline or octopine. Although octopine or nopaline could also not be detected in normal tissues of Kalanchoë, teratomata and aberrant looking roots developing from tumors do contain the same type of guanidine derivative as present in the tumor from which they develop. This suggests that once synthesis of the unusual guanidine compounds has started in the plant cells as a result of tumor induction, the control system regulating gene expression in each state of differentiation of a cell does not repress the genes coding for these compounds. For the moment, a mechanism of gene addition, i.e. the acquisition of plasmid genes by the plant cells, seems to be less remote to explain the data obtained. However, no direct biochemical data exist to support this theory. Other possibilities are discussed. The isolation of the Oct mutants of A. tumefaciens might help to distinguish between the different theories. A procedure to enrich for auxotrophic and fermentation mutants of A. tumefaciens has been developed