Like with all GMO discussions, it is important to look at this question from a sufficiently broad perspective. In this case we should realize that most of the plant derived food that we eat contains plant viruses, plant virus RNA or DNA and plant viral proteins, usually of course in small quantities. Hence there is nothing new and nothing dangerous to a transgenic plant containing a plant viral sequence: we have been exposed to plant viruses since the beginning of mankind. Moreover plant viruses do not infect humans and human viruses differ substantially from plant viruses. Regarding the comment of David Athuhaire: there is overwhelming scientific evidence that the techniques of genetic modifcation per se do not harm human/animal health nor the environment. Of course there are a few papers and quite a lot of questionable websites that claim the opposite; but please look at the facts and the scientific consensus and not to bogus reports from people with hidden agendas. In this regard, an interesting editorial was published in the Science issue of September 20th 2013, entitled "Standing up for GMOs" and signed by 11 of the most eminent scientists, most of which are not plant biotechnologists (Science, volume 341: p. 1032)

I strongly agree. You need to get the AAEM article and read. “The American Academy of Environmental Medicine (AAEM)* recently released its position paper on Genetically Modified foods stating that "GM foods pose a serious health risk" and calling for a moratorium on GM foods. Citing several animal studies, the AAEM concludes "there is more than a casual association between GM foods and adverse health effects" and that "GM foods pose a serious health risk in the areas of toxicology, allergy and immune function, reproductive health, and metabolic, physiologic and genetic health."

AFAIK, the use of a viral promotor (piece of sequence thats attractive for gene transcription proteins) does not mean that viral proteins will be expressed. In that case the genetic code for the viral protein must be directly adjecent to the viral promotor (which is not the case, its replaced with the gene of interest).

Exactly as Jeroen wrote, just because you use promoter from virus doesn't mean you get virus proteins.

You probably consume more pathogens in your "normal" food than in GMO, so I wouldn't be concerned of this issue.

@david, Those issues are with "foreign" proteins being expressed in foods most likely under the host's (or viral) promotor. If the topic starter meant to voice his concern about that issue...then the question was all wrong imo.

Like with all GMO discussions, it is important to look at this question from a sufficiently broad perspective. In this case we should realize that most of the plant derived food that we eat contains plant viruses, plant virus RNA or DNA and plant viral proteins, usually of course in small quantities. Hence there is nothing new and nothing dangerous to a transgenic plant containing a plant viral sequence: we have been exposed to plant viruses since the beginning of mankind. Moreover plant viruses do not infect humans and human viruses differ substantially from plant viruses. Regarding the comment of David Athuhaire: there is overwhelming scientific evidence that the techniques of genetic modifcation per se do not harm human/animal health nor the environment. Of course there are a few papers and quite a lot of questionable websites that claim the opposite; but please look at the facts and the scientific consensus and not to bogus reports from people with hidden agendas. In this regard, an interesting editorial was published in the Science issue of September 20th 2013, entitled "Standing up for GMOs" and signed by 11 of the most eminent scientists, most of which are not plant biotechnologists (Science, volume 341: p. 1032)

we however are exposed to the viral DNA...the food we eat daily also contains foreign proteins,but we do not mount an immune response against them coz we have developed tolerance towards them..its the same idea behind why vaccines are best when given in a single does and if boosters are required,they are well spaced over a certain period of time..if a vaccine booster was to be given lets say annually,we would develop tolerance to that particular antigen and when we are encountered with the real threat of an infection,our immune system may not respond as an all too frequent encounter with a particular antigen causes tolerance.It is also true that plant viruses may have no effect on human,but what since exist in families within which they share similarities,what happens when a human pathogenic pararetrovirus infects an individual who over time has been developed tolerance to viral DNA...the viral protein may not be there as you have previously explain,no protein is produced from the transcription of the promoter...but the DNA sequence of the promoter in itself can and may be identified as an antigen..right?

Plant viruses do not infect humans because they lack the mechanisms for entering into mammalian cells. I also disagree that we do not mount an immune response to the food that we eat. Food allergies are a direct result of the immune system recognizing a protein in a given food and mounting a defense reaction (http://nysaap.org/blog/foodallergy.pdf). We also develop antibodies to the plant viruses that we eat which may or may not cause an allergic reaction (http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0010041). It is doubtful that the CaMV 35s promoter DNA would survive the stomach acid to even serve as an antigen. Remember, this is from a plant virus that people have been unknowingly eating for who knows how long and it hasn't caused problems yet.

What are the pararetroviruses that infect humans and how closely related to CaMV are they?

Human (and animal) pararetroviruses belong to the family Hepadnaviridae (such as the Hepatitis B virus) and have dsDNA genomes of about 3.2 kb in size. The virions are icosohedral with a lipid envelope and part of the genome is single stranded (http://viralzone.expasy.org/all_by_species/9.html). Plant pararetroviruses belong to the family Caulimoviridae and have larger dsDNA genomes of 7-8 kb. The virions are either icosahedral or bacilliform (http://viralzone.expasy.org/all_by_species/96.html; http://viralzone.expasy.org/all_by_species/119.html; http://viralzone.expasy.org/all_by_species/120.html)

These two families are very distantly related at best with the only real similarities being the use of a reverse transcriptase, a dsDNA genome, and integration into the host genome. Caulimoviruses also require an arthropod vector to be transmitted while hepadnaviruses require no vector. They are very different and should not really be compared to each other. Besides, if you have ever eaten sugarcane, figs, chocolate from West Africa, or bananas from anywhere other than South America then you have consumed both integrated and episomal plant pararetroviruses.

Look at the otherside of this. Passive immunity. In England we are currently having our yearly scramble to vacinate elderly people against flu. There is a corrilation between elderly isolated people and their suseptabilty to disease. Undoubtedly most of this is down to the deteriorating health that lead them to become isolated from the community, however, what if a lack of exposure to low level semi-deactivated viruses on a day to day basis also contibutes to a higher level of suseptability. What if we need constant exposure to keep our systems strong? there was an interesting study of tube travellers who should have been lousy with disease due to the close confines of people and disease. The infection rates were no higher than the rest of the community. Children have the highest spread hence "bug farms" as a nick name, often the parents of small children with developing immune systems, though they seem to be sick all the time, have the best response in terms of the immune system. Plant virus passive immunity. (sorry about the spelling)

thanx guys, AG Laney,that's a very clear explanation...thanks alot

All DNA and protein we eat is foreign (unless you count self cannibalism).

Our bodies become tolerant to these antigens when we start to eat them at birth and the varying tolerances/intolerance to various molecules is extremely difficult to answer, and is dependent on many variables, age, dosage etc.

Addressing the specific question above, the promoter is the DNA which affects the expression of the gene in question and is not encoded into protein. Therefore it will not be present nearly as much quantity as the protein it encodes for. think of the DNA as the printing press and the proteins are the newspapers.

Our bodies will hardly even notice the 'printing press' template DNA compared to the protein, and as stated in above answers it will be quickly degraded early in the digestive system regardless. The proteins however may survive and cause immune responses leading to tolerance/intolerance.

Therefore the type/source/target and desired response to these proteins need to be addressed before even attempting to answer this question in regards to proteins. But in regards to the DNA it is quite clear from the reasons i gave and others (in particular the argument that most things we eat are made up of viral DNA) there is no cause for concern.

***Also a quick note, that although I said DNA templates are usually ineffectual in terms of tolerance and readily degraded, there is always a possibility of the DNA being taken-up by certain cells and consequently expressing and producing foreign proteins which CAN cause tolerance/intolerance issues, this is the whole basis of gene therapy and immuno-suppression. For this to even work efficiently, the DNA must be targeted to certain cells and it is almost never done by oral consumption. another example is the use of DNA vaccines but that is a whole other kettle of fish.

Should we not consider host specificity in infections. Speculations must lead to constructive answers. lalitha kabilan