Interviews with scientists:
Omega-3 and health
Teaching Notes
Introduction and context
Omega-3 fatty acids are vital for human health. But how can we source them sustainably? Professor Johnathan Napier talks about the role that Omega-3 fatty acids play in our diets, how we currently source them from algae via fish, and how he hopes to use genetic engineering to breed plants that produce these molecules in their oils.
Teacher summary
http://intobiology.org.uk/transforming-omega-3-fatty-acids/
Fish oils are a vital component of our diet. They contain omega-3 long chain polyunsaturated fatty acids and fish oils in the diet can reduce the risk of cardiovascular disease. In general, the population of the United Kingdom is not eating enough of these omega-3 long chain polyunsaturated fatty acids.
Fish oils are normally provided in the diet by eating oily fish such as mackerel and sardines. The fatty acids found in fish oils aren’t made by the fish, the fish accumulate them by eating phytoplankton, microalgae, in their diet. Humans therefore obtain the fatty acids made by the algae indirectly, through eating oily fish, although some people take them as supplements.
One of the problems, from a nutritional point of view, is that the fatty acids found in fish oils are not the same as the fatty acids found in vegetable oils, so vegetable oils do not act as a direct replacement for fish oils. Although some vegetable oils do contain omega-3 fatty acids, they are not the same omega-3 fatty acids that you find in fish oils. Omega-3-rich oil, such as flax or linseed oil can be included in the diet, but it doesn’t give the reduced risk of cardiovascular disease, which is only obtained from fish oils.
Fish farming is a great way of producing animal protein for human consumption, but it is essential that the diet of the farmed fish contains omega-3 long chain polyunsaturated fatty acids. About 80% of all the fish oil that comes out of the oceans every year (about one million tons), goes to feed other fish in fish farming. If an alternative, sustainable source of these omega-3 long chain polyunsaturated fatty acids could be found, it could perhaps be used that to replace some of the fish oils that are being put into fish farming, leaving more for direct human consumption.
A solution to the problem of sourcing a sustainable supply of omega-3 long chain polyunsaturated fatty acids is to make a genetically modified crop plant that has the capacity to make these fish oils. Vegetable oils do not contain any omega-3 long chain polyunsaturated fatty acids, so if plants can be engineered to make these fatty acids, to give them a completely new capability, then maybe genetically modified plants can be an alternative, sustainable, terrestrial source of fish oils.
The process of making fish oils in a GM plant is counter-intuitive, as genes from the fish are not needed to make the fish oil. Fish oils aren’t made by fish, they are made by algae in the marine environment. Instead, the genes from the algae need to be put into the plants to allow the plant to have the capacity to make these omega-3 long chain polyunsaturated fatty acids. This has been a long-term strategic project at Rothamstead. The idea was first suggested in the mid-1990s, and more than 15 years later, the research can be seen to be reaching the goal that it was set and moving out from the lab and into the field.
Understanding basic lipid metabolism and biochemistry has been key to the success of this project. Thin layer chromatography (TLC) has provided a powerful tool to use in the study of lipid metabolism. The different lipids found in any species can be separated out using TLC, giving the information that is needed to understand the system to be manipulated. In addition to the fairly old technique of TLC, advanced tripole and quadrupole ion trap mass spectrometry is also used to look for lipids.
Initially, most of Professor Napier’s research was carried out using Arabidopsis thaliana as a model system. This was because Arabidopsis is easy to transform, it grows quickly and would provide the information needed to then move forward and translate the research into a crop plant. Model systems are really useful, but if the research is to make a difference, then ultimately it will have to move from a model, into a crop, in this case Camelina.
Professor Napier’s research uses Agrobacterium to introduce the algal genes into their GM crop. Agrobacterium is a natural, soil-borne bacterium that can move DNA from itself into a plant. The algal genes are put under specific promoters that only allow the genes to be expressed in the seed of the Camelina, and Agrobacterium is used to move the algal genes into the Camelina plant. The Camelina plants then take on the algal genes and ultimately they are able to make the omega-3 long chain polyunsaturated fatty acids. The Camelina plants have slightly bettered the levels of omega-3 long chain polyunsaturated fatty acids that are found in fish oils, so the research has now successfully made a terrestrial source of fish oils in the genetically modified Camelina.
This area of research presents huge opportunities. There are many advances in metabolic engineering and synthetic biology, and these emerging technologies will be applicable to trying to engineer plants to make useful and important products for human health and nutrition. There are great opportunities, as there is great deal of exciting research to be done.
Questions
1. Why are fish oils important in the diet of humans?
They contain omega-3 long chain polyunsaturated fatty acids and fish oils in the diet can reduce the risk of cardiovascular disease.
2. Oily fish don’t synthesise the omega-3 long chain polyunsaturated fatty acids found in their oils themselves. Where do they come from?
The fish accumulate them by eating phytoplankton.
3. Why don’t vegetable oils act as a direct replacement for fish oils?
Some vegetable oils do contain omega-3 fatty acids, but they are not the same omega-3 fatty acids found in fish oils. An omega-3-rich oil, such as flax or linseed, doesn’t give the health benefits, the reduced risk of cardiovascular disease, which is only obtained from fish oils.
4. What percentage of fish oil that comes out of the oceans every year is it estimated goes to feeding other fish in fish farming?
About 80%.
5. If GM crops could produce an alternative, sustainable source of omega-3 long chain polyunsaturated fatty acids, what could these fatty acids be used for?
They could perhaps replace some of the fish oils that are being put into fish farming, leaving more for direct human consumption.
6. Why are algal genes put into the plants?
Fish oils aren’t made by fish. The omega-3 long chain polyunsaturated fatty acids are made by algae in the marine environment and accumulate in the fish when the fish eat the algae. Engineering the plants with algal genes allows the plant to have the capacity to make these omega-3 long chain polyunsaturated fatty acids.
7. How long has it taken for the initial idea of the research to reach its goal?
15 years.
8. Why has an understanding of basic lipid metabolism and biochemistry been key to the success of this project?
The researchers have to understand the system that they are trying to manipulate if they are to devise ways of manipulating it.
9. What is the role of Agrobacterium in Professor Napier’s research?
Agrobacterium can move DNA from itself into a plant. It is acting as a vector.
10. Why are the algal genes that are used to transform the Camelina put under specific promoters that only allow the genes to be expressed in the seeds of the Camelina?
This ensures that it is only the seeds of the Camelina that contain the omega-3 long chain polyunsaturated fatty acids, as these will be harvested and the oil extracted from them.
Science & Plants for Schools: www.saps.org.uk
Interviews with scientists – wheat genome and yield: p. 1