Using flux control analysis to improve oilseed rape

油料作物是最重要的农产品之一。在英国（以及北欧和加拿大），油菜是主要的油料作物，在世界范围内，它约占石油和脂肪总产量的12%。对植物油的需求不断增加，不仅用于人类食品和动物饲料，而且还用作化学品和生物燃料的可再生来源。在过去的40年里，这种增长的需求每8年翻一番，并且在未来很可能至少会继续以这种速度增长。在农业用地有限的情况下，增产的主要途径是提高产量。这可以通过传统育种来实现，但在未来，显著的增强将需要基因操作。后一种技术还将允许对石油产品进行特定的改性。为了进行知情的基因操作，需要对植物油的生物合成有全面的了解。至关重要的是，这将包括如何控制对石油质量和数量的监管。在植物种子中合成储存油类似于工厂的生产线，其中原材料的供应，部件的制造和最终组装都可能限制生产速度。最近，我们首次对油菜储油积累的总体调控进行了实验研究，并采用通量控制分析的数学方法对其进行了分析。这表明，最终组装是生物合成过程中最重要的限制。组装过程需要几个酶的步骤，我们已经强调了其中一个，二酰基甘油酰基转移酶（DGAT），作为一个重要的控制因素。我们现在希望检查酶，除了DGAT，参与储存脂质组装和组成部分的供应。这将使我们能够量化该途径中不同酶所施加的限制，此外，将为支持遗传操作的逻辑步骤提供信息，从而提高植物的油合成和储存能力。我们将使用生物合成途径中单个酶的活性被改变的油菜植物，并量化其对总体油积累的影响。首先，我们将使用现有的转基因油菜，随着酶水平的提高，已经注意到石油产量的增加；这些是我们的合作者（加拿大，德国）提供的。对于目前没有转基因植物的酶，我们将制作这些并进行类似的分析。虽然我们的主要重点是增加油脂产量的酶，但我们也将研究磷脂酶：二酰基甘油酰基转移酶（PDAT）对油脂生产的贡献，因为这种酶控制不饱和油脂的积累，这对饮食有重要的影响。在拟南芥中，PDAT和DGAT在产油过程中都起重要作用。一旦我们收集了这些转基因植物的数据，我们将对控制油菜的脂质产生有更好的了解。我们的定量测量将为未来作物改良提供具体目标。此外，由于我们将监测石油产量和通量控制，我们将能够将这两项措施联系起来。此外，对植物进行多基因操作（基因堆叠）将揭示这些策略是否存在协同效应。由于还没有人定量地定义作物中的油合成途径，该项目产生的数据将对基础科学产生根本性影响。通过结合英国三个重要实验室的专业知识。与我们世界领先的国际合作者，这个跨学科项目将确保知识直接应用于农业的重大进步。

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 and biofuels. 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. The synthesis of storage oil in plant seeds is analogous to a factory production line, where the supply of raw materials, manufacture of components and final assembly can all potentially limit the rate of production. Recently, we made a first experimental study of overall regulation of storage oil accumulation in oilseed rape, which we analysed by a mathematical method called flux control analysis. This showed that it is the final assembly that is the most important limitation on the biosynthetic process. The assembly process requires several enzyme steps and we have already highlighted one of these, diacylglycerol acyltransferase (DGAT), as being a significant controlling factor. We now wish to examine enzymes, other than DGAT, involved in storage lipid assembly and in supply of component parts. This will enable us to quantify the limitations imposed by different enzymes of the pathway and, furthermore, will provide information to underpin logical steps in genetic manipulation leading to plants with increased oil synthesis and storage capabilities. We will use rape plants where the activity of individual enzymes in the biosynthetic pathway have been changed and quantify the effects on overall oil accumulation.To begin with we will use existing transgenic oilseed rape, with increased enzyme levels, where increases in oil yields have been noted; these are available from our collaborators (Canada, Germany). For enzymes where there are no current transgenic plants available, we will make these and carry out similar analyses.Although our primary focus is on enzymes that increase oil yields, we will also examine the contribution the enzyme phospholipid: diacylglycerol acyltransferase (PDAT) makes to lipid production because this enzyme controls the accumulation of unsaturated oil, which has important dietary implications. In the analogous model plant Arabidopsis, PDAT and DGAT are both important during oil production.Once we have assembled data from these transgenic plants we will have a much better idea of the control of lipid production in oilseed rape. Our quantitative measurements will provide specific targets for future crop improvements. 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 strategies. Because no one has yet defined quantitatively the oil synthesis pathway in crops, data produced in the project will have a fundamental impact in basic science. By combining the expertise of three important U.K. labs. with our world-leading international collaborators, this cross-disciplinary project will ensure a significant advance in knowledge of direct application to agriculture.