With the Council for Science and Technology advising that we need to rethink our stance on GM food, we decided to look into some of the science behind genetic engineering to see what all the fuss is about.
Every year the world population increases, as does our need to find new sources of food. Globally malnutrition affects 34 million children across the world- but could GM crops be the cure? A huge proportion of land is simply not good enough to grow food or has problems with pests, but if we could change how crops react to these stresses and give them added genetic protection then we could provide new food sources to those who need it. Some plants could be enhanced in certain vitamins, such as Golden Rice which provides additional vitamin A, essential for human development, vision and immunity. There is even the possibility to use these plants medically as a delivery system for vaccinations.
The majority of GM crops are grown in the USA, Brazil, Argentina, Canada and India. But why is Europe so opposed to engineered crops? Last year Monsanto (one of the biggest GM seed companies) finally gave up trying to get Europe to approve the growth of new strains of GM crops, and instead decided to focus on importing them instead. At the moment only one strain is actively being grown, MON810 Maize, and even though it is deemed safe very few European countries are allowing its use.
Putting aside the politics and ethics of GM crops, how do we actually generate these plants? Here’s a little information on some of the science behind genetic engineering.
So how do we actually genetically engineer plants? One way in which plants have been adapted is by the use of Agrobacterium. This bacteria in its natural habitat is the cause of crown gall disease, a plant disease characterised by the formation of swellings on plant roots, stems and branches. It does this by transferring its own DNA into the plant cells, meaning its a natural plant engineer! Scientists have used Agrobacterium for years to integrate DNA coding for desired characteristics (pesticide tolerance, insect repellent, etc) into the plant genome. Plants which have taken up the DNA are then selected and the bacteria killed using an antibiotic. Plant hormones and nutrients are provided to help the newly transformed plants grow.
DNA transfer using bacteria isn’t as simple as it sounds as there are a number of things that can interfere with the process. Whilst not as complex as our own, some plants offer up an “immunity” against agrobacterium by variations in their cell wall. For plant species that don’t work well with bacterial DNA transfection (such as cereals and legumes), direct transfer is a way of getting DNA into cells. This method shoots DNA-coated particles into cells using a biolistic particle gun. The main drawback with this method is that it isn’t very efficient. About 1/100 bombarded plant embryos will become GM plants.
RNA interference (RNAi) uses short RNAs that target certain mRNA for degradation via the RNA-induced silencing complex, or RISC. This causes silencing of genes by preventing the proteins they code for from being synthesised, and has been shown to be useful in providing plants with resistance against viruses. This process occurs naturally in a number of different organisms but can be hijacked by scientists to give plants environmental advantages. It’s interesting to note that RNAi is also being looked in to medically as a way of treating diseases, although it’s a lot harder to manipulate humans than it is plants.
Modifying plants is tricky business, and that’s why a huge amount of money is ploughed into researching these new crops, and even more into safety testing them. Plant toxicity is measured, as well as any allergic reaction it may cause. The newly introduced DNA can only code for protein accounting for 0.08% of the total seed protein, which is a tiny fraction. There are still issues with the technology, such as the genes transferring into weeds in the wild which would give them an advantage (such as pesticide resistance) allowing them to outcompete other plants. This has been the case with overuse of the herbicide glyphosate (also known as Roundup) with plants modified to be resistant to the chemical. Weeds eventually gained resistance to the herbicide and destroyed a huge proportion of the crop. These risks can be reduced by rotation of different herbicides in plants with “stacked” resistance to a number of different chemicals.This problem mimics the issues we’re having with antibiotics where bacteria are becoming increasingly resistant to these drugs. Eventually there is the worry that an MRSA like weed may appear that is resistant to all of our common herbicides and that would out-compete crops.
The debate for and against GM crops is huge, and something we should all have an opinion on. All we ask is that before you speak, you read the facts and form your own ideas!
If you want to read more:
20 questions you might ask about GM food. This was written by the World Health Organisation, and may answer some of your questions about GM crops: http://www.who.int/foodsafety/publications/biotech/20questions/en/
Eamens A, Wang MB, Smith NA, & Waterhouse PM (2008). RNA silencing in plants: yesterday, today, and tomorrow. Plant physiology, 147 (2), 456-68 PMID: 18524877
Funke T, Han H, Healy-Fried ML, Fischer M, & Schönbrunn E (2006). Molecular basis for the herbicide resistance of Roundup Ready crops. Proceedings of the National Academy of Sciences of the United States of America, 103 (35), 13010-5 PMID: 16916934
Paine JA, Shipton CA, Chaggar S, Howells RM, Kennedy MJ, Vernon G, Wright SY, Hinchliffe E, Adams JL, Silverstone AL, & Drake R (2005). Improving the nutritional value of Golden Rice through increased pro-vitamin A content. Nature biotechnology, 23 (4), 482-7 PMID: 15793573