Fats and oils – an introduction
Fats and oils (sometimes collectively called “lipids”) are perhaps most familiar to us as a form of energy in our diets, but they also serve a variety of other important roles. Our bodies use lipids to form the structure of our cells and to perform many of the biological processes that are essential to our health.
In plants, particularly oilseeds, lipids provide the energy required to support seed germination -- a kind of energy “reserve” that supports the plant’s early growth. Because this stored energy is so important for survival, oilseed plants have evolved an efficient biochemical system for producing and storing lipids. This also makes oilseeds tremendously useful for humans – as a source of both edible oil and as a raw material for the production of many industrial products that we use every day, such as inks, paints, lubricants, and biofuels.
Before we describe how Phytola is working to modify seed oils for specific nutritional or industrial applications, it may be helpful to first understand more about how seed oils are actually formed.
The biochemistry of seed oil formation
The building blocks of oils and fats are called “fatty acids” – individual chains of carbon that come in various lengths and degrees of “saturation.” A saturated fatty acid is a rigid, linear chain, and it’s this property that makes highly saturated fats (like butter) remain solid at room temperature. “Unsaturated” fatty acids, on the other hand, have a slight kink or bend in the chain that allows them to be more flexible – think of how canola oil is a liquid at room temperature. “Polyunsaturated” fatty acids contain multiple bends or kinks and have many unique properties that are especially important for our health.
All fats and oils are made up of different combinations of saturated and unsaturated fatty acids that are assembled into larger molecules called “triacylglycerols” – literally meaning three (tri) fatty acids (acyl) attached to a glycerol backbone (glycerol). Triacylglycerols (or TAG for short) are the primary form of stored lipids in plants. From a biochemical perspective, it is useful to think of seed oil formation as two processes: 1) fatty acid formation and 2) assembly of fatty acids into TAG. Either or both of these processes can be targeted through biotechnology to modify the quantity and the composition of oil in a plant.
Modifying fatty acid composition
Most common plant oils (e.g., canola, flax, soybean, corn, etc.) contain a limited number of different fatty acids. Although they occur in different proportions within each type of oil, there are only about 5-6 “common” fatty acids that make up the majority of the commodity vegetable oils. Elsewhere in nature, however, there is a much wider diversity of fatty acids – hundreds of different fatty acids, each with their own unique properties. Many of these unusual fatty acids would be ideal for specific industrial or nutritional applications, but their distribution in nature is limited to a few species, which makes it difficult to obtain sufficient and sustainable supplies for human use.
Through biotechnology, we can use oilseed crops as “factories” for the production of unusual fatty acids, thereby providing an abundant and sustainable source of these specialty oils. Although Phytola works on a number of different unusual fatty acids, a good example to illustrate this approach is the production of very long chain polyunsaturated fatty acids similar to those found in fish oils.
You may have heard about the health benefits of consuming so-called “omega-3” fatty acids from fish oil. The two fatty acids in fish oil that provide these benefits are eicosapentaenoic acid (EPA for short) and docosahexaenoic acid (DHA for short). EPA and DHA are critical for early infant development, immune system function, and many other biological processes. But our bodies produce limited quantities of EPA and DHA, which means we must consume them as part of our diet – most commonly fish or other products that have been enriched in these fatty acids.
Unfortunately, due to a variety of environmental and management pressures, the world’s fisheries are increasingly being threatened, while demand for fish oil has never been greater. This has created an urgent need to develop a sustainable supply of these high-value fatty acids.
The fatty acids found in fish are actually produced by microorganisms that the fish eat and accumulate in their bodies. The microorganisms that produce EPA and DHA use similar biochemical machinery as oilseeds, but it is highly specialized for the production of these particular fatty acids. By taking the genetic “blueprints” for this machinery and transferring it into oilseed crops, we can engineer oilseeds to begin producing these new fatty acids – more sustainably, and in larger quantities than could be harvested from marine sources.
Phytola’s research currently focuses on increasing the accumulation of unusual fatty acids in oilseed crops, by developing a better understanding of the biochemical “bottlenecks” that limit or block certain steps in the pathway, and then testing new approaches to overcoming those limitations. We also collaborate with other researchers, including human and animal nutritionists, who study the nutritional effectiveness of new specialty oils.
Increasing seed oil content
In addition to creating “designer” oils with specific fatty acid compositions, Phytola is also working toward increasing the overall amount of oil that can accumulate in canola seeds. Increasing seed oil content in canola is important for meeting the rising global demands for vegetable oil, but it also adds significant value to the crop. It has been estimated, for example, that just a 1% increase in the seed oil content would be worth more than $90 million annually for Canada’s canola industry.
Seed oil content is determined by a number of factors, including genetics, environmental conditions, and farming practices. From a biotechnological perspective, increasing seed oil content typically involves targeting the process of TAG assembly – the pathway that packages fatty acids into seed oil.
For more than 20 years, Phytola’s Scientific Director, Dr. Randall Weselake, has specialized in studying the biochemical machinery of TAG assembly, and has been particularly focused on the final step of the pathway. This step, carried out by an enzyme called diacylglycerol acyltransferase (or DGAT), has been shown to limit oil accumulation in canola seeds, and we have found that increasing the amount of DGAT in the seeds results in higher seed oil content. This finding has prompted us to explore other ways of increasing the activity of DGAT and other related enzymes.
Currently, our work focuses on understanding the molecular structure and function of DGAT, and using that knowledge to introduce specific changes to the structure of the enzyme in order to enhance its function. The goal is to produce a highly efficient form of DGAT that can support greater levels of oil accumulation. This research could also be the basis for applying similar approaches to other oil-synthesizing enzymes.
Although Phytola works on a number of different oilseed species, canola improvement continues to be major focus – it is Canada’s most valuable oilseed crop and perhaps the nation’s most familiar agricultural success story. Canola oil is used widely for both edible and industrial applications – its high level of unsaturated fatty acids makes it highly nutritious, and its low levels of saturated fatty acids (the lowest of all commodity vegetable oils) makes it ideal for certain industrial applications, such as biodiesel. The Canadian canola industry has also fully embraced biotechnology as a tool for novel trait development, which allows us to work within a well-established system for introducing new traits to the market.
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