Chardon Report II - Hazards Arising From The Use Of The CaMV Promoter In Genetic Engineering

Report II, May 2002


[PDF version of the full report (62KB)]


In 1999, a paper was published that warned of possible hazards arising from the common use in genetic engineering of a promoter (a gene that switches the functioning of other genes on or off) obtained from the cauliflower mosaic virus (CaMV). Other authors raised objections to this paper; but these objections were countered in a further paper by the first authors. A brief additional paper by these authors followed later. This report quotes each successive objection and then quotes the rebuttal(s). In a few cases, where a rebuttal does not appear in the published papers, we have supplied one from elsewhere.

The papers are:

Paper 1: Mae-Wan Ho, Angela Ryan and Joe Cummins, ‘Cauliflower Mosaic Viral Promoter — A Recipe for Disaster?’, 1999, Microbial Ecology in Health and Disease, 11, 194-197

Paper 2: R. Hull, S.N. Covey and P. Dale, ‘Genetically modified plants and the 35S promoter: assessing the risks and promoting the debate’, 2000, Microbial Ecology in Health and Disease, 12, 1-5

Paper 3: Mae-Wan Ho, Angela Ryan and Joe Cummins, ‘Hazards of transgenic plants containing the cauliflower mosaic viral promoter’, 2000, Microbial Ecology in Health and Disease, 12, 6-11

Paper 4: Mae-Wan Ho, Angela Ryan and Joe Cummins, ‘CaMV 35S promoter fragmentation hotspot confirmed, and it is active in animals’, 2000, Microbial Ecology in Health and Disease, 12, 189.

Relevant concepts from molecular Biology: Definitions relevant to this report are provided.

Paper I: A Recipe for Disaster?

The promoter has three domains, containing subdomains capable of functioning together in ways producing effects greater than the sum of the individual effects. Various pieces of the promoter can be (and have been) manipulated individually to construct hybrid or combination promoters. Thus there is the possibility that elements of the promoter could combine with dormant viruses in host plants to produce new, infectious viruses. The similarity of CaMV to viruses like hepatitis B is of particular concern.

Of especial concern is the removal, in genetic engineering, of the natural viral coating. In its natural state, the CaMV virus is able to enter and infect only a limited range of plants. Without the coat, as in the GM promoter, all species, including animals and human beings, become susceptible. Furthermore, the promoter contains a ‘recombination hotspot’, where interactions with other DNA can readily occur. The strength of the promoter may also result in continuous overactivity of genes, a consequence of which could be cancer. The instability of transgenes [genes inserted by genetic engineering] is also likely to be exacerbated.

The properties of the promoter that make it so useful in genetic engineering also facilitate recombination events and mobilisation of genes out of the host into its environment. This process of horizontal gene transfer could cause unpredictable and large-scale rearrangements of genes. The authors believe that all crops and products containing the CaMV promoter should be withdrawn.

Papers 2 and 3

Objections to Paper 1 are extracted from Paper 2, and rebuttals from Paper 3 (or elsewhere) are quoted in turn. Because these are technical papers, no summary is given here.

Summary of Papers 3 and 4

The arguments given above are re-emphasized. (Paper 4 is very short and nearly the whole of this section comes from Paper 3.)