THE cultivation of genetically manipulated crops is expected to reap considerable benefits for agriculture, Yet each “new” gene also carries with it possible dangers for the environment and its inhabitants, Consequently, it is vital to identify any possible risks prior to large-scale application by implementing programmers of impact-assessment research.
In plants, nitrogen is an essential building block for protein and genetic material. One of the many enzymes involved in the development of these compounds is glutamine synthetize (GS) which is common in carriers of chlorophyll, GS converts the nitrogen, present in the form of ammonium, into glutamate, which is then converted into glutamine, This reaction is targeted by the herbicide Basta, which has been developed by the pharmaceuticals giant Hoechst AG in Frankfurt. Containing an agent known as phosphinotricine this substance inhibits the GS, which reduces the quantity of glutamine in the cells and increases concentrations of toxic ammonium, leading to the death of the affected cells and eventually of the whole plant.
AS a so-called “blanket herbicide which attacks the plant through its leaves, “Basta” can only be sprayed before the crops have developed leaves. In order to prolong the agents’ effectiveness. The Frankfurt researchers have implanted into the genetic material of the crop a gene extracted from the soil bacteria Streptomyces viridochromogenes. Known as the phosphinotricine acetyltransferase gene (PAT) this gene triggers the formation of an enzyme which while rendering the herbicidal agent harmless to the transgenic crop, does not impair its effectiveness against no modified plants. Dr. Inge Broer from the Faculty of Genetics at the University of Bielefeld has recently reported on her research into the impact of genetically manipulated plants, One of the major problems in cultivating transgenic plants is that on being released into nature, the foreign gene could spread uncontrollably as a result of vertical (sexual) or horizontal gene transfer. Sexual gene transfer corresponds to normal reproduction in flowering plants. Horizontal gene transfer, however, in which the genetic material of one organism is transferred to that of another species, is found primarily in microorganisms for example, in bacteria which absorb free deoxynbose nucleic acids, DNA, the carrier of genetic material. Under certain conditions, a number of viruses are capable of transferring DNA from one bacterium to another, ‘This raises the question of
Whether genetic material from genetically modified plants could be transferred to non-related species or be released during the decomposition of plants and taken up by soil bacteria Theoretically. this PAT gene could eventually be transferred to-some species of wild plant, rendering it resistant to her bicidal agents such as “Basta’’ However, Dr Broer. and Professor Alfred Puhler have concluded that although “horizontal gene transfer from a plant into another organism cannot be ruled out, it is extremely improbable.”
Against general expectations, a number of scientists observed some years ago that freely avail-‘ able DNA remains stable in the! soil for a long period, suggesting’ that a bacterium could accidentally absorb a piece of DNA. This could bestow upon the bacteria a resistance to antibiotics which commonly serve as markers in genetic engineering for accurately tracing the modified organism. According to Dr. Broer, it is therefore essential to analyze the impact of the plant’s phosphinotricine metabolites on the quality and integrity of newly-created nutrients. Environmental organizations was that the “cultivation of transgenic crops is precipitating a rapid reduction in the diversity of both cultivated and wild I crops” Cultivated crops, because this technology only uses the easily modified variety of a particular species; wild crops, because blanket herbicides indiscriminately kill all nonresistant flora, expense has shown that irrespective of the impact of gene transfer herbicides ” only remain active for a limited time: Sooner or later, the process” of natural genetic mutations produce a new variety of, weeds which is resistant against the agent.
The gene transfer is not the only grave danger. Equally lethal is the indiscriminate use of chemicals.
to be continued
Article extracted from this publication >> July 22, 1994
