Engineering root architecture using a predictive integrative systems biology approach

粮食安全是一个重大的全球问题。这也是上个世纪中期的一个主要问题，当时粮食生产跟不上人口增长的步伐。在后一种情况下，植物育种者能够开发出新的高产矮秆水稻和小麦品种，这些品种对高投入的肥料有反应。所谓的“绿色革命”带来了50年的粮食安全。然而，西方社会越来越要求农业通过减少化学投入变得更加可持续;而在发展中国家，农民几乎无法获得化肥，需要可以在贫瘠土壤中生长的作物。在这两种情况下，开发提高养分利用效率的作物将提供解决方案。根构型严重影响养分和水分的吸收效率。例如，生根深度影响土壤氮（和水）的有效获取，因为硝酸盐渗入土壤深处。与此相反，磷酸盐利用效率可以显着提高，而不增加根深，通过操纵根生长的角度，以更好地探索这种大量营养素积累的表土。尽管有这些知识，但植物育种家在主要谷类作物中并没有选择根构型作为性状。然而，通过操纵根构型来提高作物养分利用效率的需求变得越来越迫切。它对世界农业的影响是如此之大，以至于作物科学家乔纳森·林奇呼吁进行一场以根系结构为重点的“第二次绿色革命”，这应该成为“21世纪植物生物学的优先事项”。这项研究计划旨在首先确定简单植物拟南芥中调节根结构的基因，然后利用这些信息操纵谷物中的等效基因，最终目标是改变其根结构并提高养分利用效率。这项雄心勃勃的研究计划依赖于一种新的基于X射线的技术（称为Micro-CT），可以对土壤中活根的3D排列进行成像。我们将使用Micro-CT技术来鉴定具有改变的根排列的拟南芥突变体（缺少特定基因）。这将使我们能够准确地确定哪些基因调节根结构。在谷类作物中鉴定等同基因相对简单，因为大麦和水稻与拟南芥是远亲。然后，我们将使用先进的遗传技术来克隆这些大麦和水稻基因，然后研究它们对根结构和养分利用效率的影响。有前途的水稻和大麦品系将提供给IRRI和SCRI的专业育种者，最终目标是将其改良的根系性状渗入到优秀的作物品种中。

Food security represents a major global issue. This was also a major problem in the middle of the last century when food production failed to keep pace with population growth. In this latter case, plant breeders were able to develop new high yielding dwarf varieties of rice and wheat that responded to high inputs of fertilisers. The so-called 'Green Revolution' has delivered 50 years of food security. However, western societies are increasingly demanding that agriculture becomes more sustainable, through reductions in chemical inputs; whilst in the developing world, farmers with little access to fertilisers, need crops that can grow in infertile soils. In both cases, developing crops with improved nutrient use efficiency would provide the solution. Root architecture critically influences nutrient and water uptake efficiency. For example, rooting depth impacts the efficient acquisition of soil nitrogen (and water) since nitrate leaches deep into the soil. In contrast, phosphate use efficiency could be significantly improved without increasing root depth by manipulating the angle of root growth to better explore the top soil where this macronutrient accumulates. Despite this knowledge, root architecture has not been a trait selected for by plant breeders in major cereal crops. However, the need to improve nutrient use efficiency in crops through manipulating root architecture is becoming increasingly urgent. Its impact on world agriculture would be such that the crop scientist Jonathan Lynch has called for a 'Second Green Revolution' focussing on root architecture, and that this should be made 'a priority for plant biology in the 21st century'. This research proposal aims to first identify the genes that regulate root architecture in the simple plant Arabidopsis thaliana, then use this information to manipulate equivalent genes in cereals, with the ultimate goal of altering their root architecture and improving nutrient use efficiency. The ambitious programme of research relies on a new X-ray based technique (called Micro-CT) that can image the 3D arrangement of living roots in soil. We will use the Micro-CT technique to identify Arabidopsis mutants (which lack a specific gene) with an altered arrangement of roots. This will enable us to pinpoint exactly which genes regulate root architecture. Identifying equivalent genes in cereal crops is relatively straight forward since barley and rice are distantly related to Arabidopsis. We will then use advanced genetic techniques to inactivate these barley and rice genes and then examine their consequences on root architecture and nutrient use efficiency. Promising rice and barley lines will be made available to professional breeders at IRRI and SCRI with the ultimate aim to introgress their modified root traits into elite crop varieties.