Original project summary
Oil crops are one of the most important agricultural commodities. In the U.K. (and Northern Europe and Canada) oilseed rape is the dominant oil crop and worldwide it accounts for about 12% of the total oil and fat production.There is an increasing demand for plant oils not only for human food and animal feed but also as renewable sources of chemicals. This increased demand has shown a doubling every 8 years over the last four decades and is likely to continue at at least this rate in the future. With a limitation on agricultural land, the main way to increase production is to increase yields. This can be achieved by conventional breeding but, in the future, significant enhancements will need genetic manipulation. The latter technique will also allow specific modification of the oil product to be achieved.
In order for informed genetic manipulation to take place, a thorough knowledge of the biosynthesis of plant oils is needed. Crucially, this would include how regulation of oil quality and quantity is controlled.ecently, we made a first study of the overall regulation of lipid accumulation in oilseed rape. Our experiments showed that it was the final assembly of oil that was the most important part of the biosynthetic process. We also highlighted the final enzyme of the pathway, diacylglycerol acyltransferase (DGAT) as being a significant controlling factor. By using a quantitative mathematical modelling method (flux control analysis), we were able to quantify aspects of the regulation.
There are several steps to lipid assembly and we now wish to examine enzymes other than DGAT. This will enable us to quantify different parts of the pathway and, furthermore, will provide information to underpin logical steps in genetic manipulation. We will use rape plants where the activity individual steps in the biosynthetic pathway have been changed and quantify the effects on overall oil accumulation.To begin with we will use transgenic oilseed rape where foreign genes have been expressed and increases in oil yields noted. This is available from our collaborators (Canada, Germany) and will allow initial measurements of the effect on flux. For steps where there are no current transgenics, we will identify and over express the oilseed rape genes in a particular commercial cultivar.
Although our primary focus is on enzymes that increase oil yields, we will also examine the contribution the phospholipid: diacylglycerol acyltransferase (PDAT) makes to lipid production because this enzyme controls the accumulation of unsaturated oil. In the amalogous model plant Arabidopsis, PDAT and DGAT are both important during oil production.
Once we have assembled data from our various transgenic plants we will have a much better idea of the control of lipid production in oilseed rape. Our quantitative measurements will allow specific advice to be given to breeders and growers. In addition, because we will be monitoring oil yields as well as flux control we will be able to correlate these two measures. Moreover, plants manipulated with multiple genes (gene stacking) will reveal if there are synergistic effects of such strategics.
Outcomes
Of the enzymes investigated by over-expression, two showed significant effects, summarised on their respective pages: