GM-free Scotland

News | March '10 | GM plum trees and various unintended consequences

Image of plumsThe US Department of Agriculture (USDA) has been busy in recent years reinventing plum trees. The novel trees have a viral gene inserted to make them generate a protein normally generated by the plum poxvirus (PPV). The hope is that any attempted invasion by this major plum pest will be kept in check by the apparent 'presence' of the virus already in the plant's genome.

Unfortunately, GM trees don't always do what they've been genetically told to do. Some of the experimental plum trees accumulated high levels of PPV protein as planned, and their transgenic DNA produced plenty of the RNA messenger molecules needed to instruct the creation of the PPV protein as planned. But, they still failed to ward off the virus in the field.

One strain of the GM tree, however, was found to be resistant to the virus. Paradoxically, this strain, designated 'C5', doesn't produce any viral protein worth having and its novel DNA generates next to no messenger RNA. The transgenic DNA of C5 could not be characterised because it has become so scrambled during insertion that the neat engineered construct now includes duplicate and inverted genes, sections of the bacterial vector used in its development, and fragments of marker DNA sequences.

What was found to be present in high concentrations in C5 was a small, unplanned, regulatory RNA molecule. It is presumed that this regulatory RNA is acting to suppress the transgene function (hence no transgenic protein and no messenger RNA) while also suppressing the same gene in any invading PPV (hence no viral infection).

This is one messed-up GMO which happens, by accident and certainly not by design, to do what's wanted. Despite its novel, novel DNA, its unknown mode of action, and an unexplained amount of an unusual RNA, US regulators have been happy to approve the GM plum.

How can any regulatory body vouch for the safety of a genetically modified, genetically scrambled, genetically impossible to understand, organism? APHIS (the US Animal and Plant Health Inspection Service) advisers succeeded in approving it by clinging to the belief that “Nucleic acids (i.e. RNA and DNA) are present in all living organisms and are not known to have any toxic properties”. Nucleic acids are “generally recognized as safe (GRAS) by the US FDA (Food and Drug Agency) ... and exempt from the requirement of a tolerance under the Federal Food Drug and Cosmetic Act” (FDA 1992) They also insist that “the safety of nucleic acids is widely accepted” as both RNA and DNA are part of all food products we consume, and “given that plant viruses infect a tremendous amount of the fruits and vegetables that we consume, it is highly likely that humans have been exposed to the same or similar viral RNA that may be expressed in a coat-protein expressing plant.”

The APHIS seems a little confused. The unusual small RNA present in the GM plums is not a viral RNA, it is produced by the plant's own DNA as a direct side-effect of the presence of the transgene. It is certainly not likely we have been exposed to the same or similar before, and it is present in high concentrations. The Institute of Science in Society has pointed out that the GRAS categorisation of nucleic acids goes back primarily to a 1992 FDA notice based on transgenic microbes used to produce animal proteins in contained conditions. This statement is irrelevant to higher organisms grown in the open environment, breathed in as dust, and eaten whole. The notice also predates GM crops, and fails to take a wealth of recent scientific discoveries about RNA into account.

For example, when laboratory mice were injected with a wide variety of small RNA molecules, researchers were surprised when 35 out of 49 (73%) were severely toxic and 23 (47%) killed all the experimental animals within two months. The animals died from liver failure, but whether this was due to a direct toxic effect of the test RNA, or to the suppression of the liver's own vital regulatory RNA system, isn't clear. Chronic exposure to an artificial over-production of small RNA molecules has never been investigated.

OUR COMMENT

Are we going to 'cure' a disease in trees and create a disease in humans?Perhaps we could apply a little scientific testing now and start learning to create health in our trees and in ourselves.

For some more titbits about nucleic acids you never wanted to know, check out 
NEW KNOWLEDGE OF THE GENOME REVEALS GENETIC MODIFICATION AS OUTDATED, AND DANGEROUS 
– News, March 2010

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