In a background paper, the UK's Advisory Committee on Releases to the Environment suggests that GM crops modified to reduce gene flow should be the aim of biotechnologists.
In a background paper, the UK's Advisory Committee on Releases to the Environment suggests that GM crops modified to reduce gene flow should be the aim of biotechnologists. "Looking to the future, there are a number of existing and emerging technologies that will help to reduce or prevent gene flow, such as modifying plants so that they do not produce pollen, do not flower or reproduce asexually," says ACRE in the paper. "ACRE has recently produced guidance on these technologies and highlighted their importance in simplifying risk assessment. It is hoped that those responsible for the production of GM crops will embrace these developments wherever possible."
In its paper "Gene Flow From Genetically Modified Crops" ACRE stresses the need to look at gene flow when considering biosafety of transgenic plants. "Evaluating the likelihood and, more importantly, the consequences of gene flow from GM crops is a major component of the risk assessment process," it says. However, the committee points out that there is more knowledge and practical experience about the likelihood of gene flow than there is about its consequences. "Where there are gaps in scientific understanding, particularly as more diverse genetic modifications come forward, then risk management will permit safe testing in a step by step process at the R&D stage. This will inform risk assessment for applications for commercial cultivation, but the onus is on the notifiers to provide robust data in support of their applications."
The paper considers the possibility of horizontal gene transfer (HGT), pointing out that researchers have found it hard to create even under favourable laboratory conditions. ACRE says is not aware of any work that has been able to show HGT from GM plants to bacteria in the field. However, ACRE says it takes the precautionary view that HGT will occur and thus concentrates on assessing the possible consequences. "As with gene flow via more accepted routes, the consequences of HGT will depend on what DNA sequences are transferred and whether they are active in the recipient bacteria. Most of the promoter sequences used to direct transgene expression in plants show little or no activity in bacteria. Gene sequences are also often optimised for codon usage in plants and express poorly in bacteria. Further, even if the transgenes were to be active in bacteria then without selection pressure they will disappear or remain at a very low frequency in the population."
ACRE has advised previously that the transfer of antibiotic resistance genes from GM crops to bacteria would be insignificant compared to the levels of antibiotic resistance that already exist in nature, particularly due to the over use of antibiotics in medicine and as prophylactics/growth enhancers in intensive animal husbandry. However, ACRE has cautioned against the marketing of GM plants and products containing genes that confer resistance to antibiotics of clinical importance. "The very small risk that the use of such crops could compromise the clinical value of important antibiotics is a risk not worth taking," says the committee.