This is a controversial subject of course. I attended a symposium sponsored by the OEFFA* here in Ohio on the subject of GMOs. There were actually pro and con presentations made.
My takeaway was to find myself more convinced by the scientists who have actually done some of this work and said that they currently cannot tell what the overall impact on the genome of the altered plants is.
As a plant physiologist with some knowledge of genetics, I know that each plant has a limited capacity for producing photosynthetic products. If precursors are diverted into the pathway to (unnaturally) produce anthocyanins, what other pathway was deprived of its precursors? Anthocyanins are chemically complex. They are soluble because they are highly glycosylated (have many sugar molecules attached). Does that reduce the sweetness of the tomato?
I found a report about the transgenic purple tomatoes compared to normal red. They were actually able to "silence" the transgene(s) in various sectors of individual fruits! Then they compared gene expression in them:
"Two hundred and forty one genes showed significant differences in expression between purple and red sectors over at least two stages (Figure S3A). Functional annotation revealed that many of these genes are involved in primary and secondary metabolism, cell wall modification, oxidative stress, and pathogen resistance."
It appears that at the time they did not know what the 240 genes affected were, exactly.
Various other articles on this subject suggest that production of the naturally occurring anthocyanins in wild tomatoes such as the ones used in breeding'Indigo Rose' could have been stimulated instead of introducing genes from Antirrhinum. My suspicion is that the reason for doing this is so that it could be patented. There are some other economic considerations though such as shelf life which could have been an impetus except I don't think it was found until after the fact:
There is a difference in the expression of the snapdragon anthocyanins - they're produced in the flesh not just the skin as in the wild ones.
One result of this is that the fruits have been found to be much more resistant to decay. So they might be able to sit on the store counter for 50 days instead of 20-30 before they rot. Woohoo? I'm ambivalent.
Ultimately I think ppl will decide whether to eat them or not based on taste and price. There is no nutritional need to eat them because anthocyanins are naturally plentiful in many "blue" and purple fruits and to a lesser extent in vegetables. Red cabbage has anthocyanins, for example.
As to other kinds of transgenic plants- some have caused ecological damage beyond the reduction of diversity mentioned by Jill
@critterologist. A plant called horse weed rapidly developed resistance to RoundUp so completely that it overwhelmed RU-resistant soybean fields.
Next step: GE Soybeans were then "stacked" with the addition of resistance to dicamba, a broadleaf herbicide that (so far) kills horse weed.
This was a highly controversial decision by regulators who permitted it. Dicamba is highly volatile. It easily drifts offsite even in low winds. Manufacturers claimed limits would be placed on its application to prevent that. So, it isn't legal to apply it when it is even slightly windy. The reality is that farmers are growing soybeans in huge fields. They can't spray only during calm days. The result has been dicamba damage to forests, natural areas, and landscapes everywhere soybeans are grown.
When the soybeans across the road from us are sprayed, the leaves on our ginkgo tree are pale and only reach 1/2" across. Development of later flushes is delayed. Growth of the entire tree has been nearly halted. Fortunately it hasn't died. Some of our herbaceous ornamentals have. Redbuds are similarly stunted. Ash and oak are affected depending on how much spray hits them.
Then there's the issue of pollen drift on wind pollinated crops like corn and canola. Organic farmers in Canada were actually sued by manufacturers because GE plants were found in their fields. Did the farmers want them? Not at all! Their organic certification was ruined by unwanted genetic contamination.
So I won't knowingly eat any genetically engineered plants because of the unpredictable consequences, in so many different ways.
Pat
*Ohio Ecological Food and Farm Association
Edited to correct a misspelled word.
