Yield improvement of oilseed rape through genetic manipulation of rhizosphere exudation

植物利用光合作用将二氧化碳固定为糖，糖用于植物生长和发育。高达50%的碳（C）被植物固定到根部，在那里它通过土壤支持根系的生长，以吸收营养和水分并推动生长。健康生长的根系将它们所吸收的大部分C作为“根沉积物”传递到土壤中。这包括一系列物质，但由有机酸（如柠檬酸）、碳水化合物（如葡萄糖）和氨基酸（如亮氨酸）组成的可溶性渗出物构成了最大的根沉积物组分。根沉积物的总量以及从根中损失的具体类型因植物物种和物种内基因型而异，并受植物发育阶段和环境参数的影响。由于根际沉积和易有效碳的存在，根周围的土壤中有大量的微生物，形成了一个独特的微生物生态位，这被称为根际。栖息在微生物中的微生物以多种方式与植物相互作用-一些是病原体或有益的共生体，另一些则参与作物营养物质（如氮（N）和磷（P））的循环和转化，改变其对植物的可用性。这些过程决定了植物的生产力，即使在农业系统中，肥料被添加到最大限度地提高产量。生长在根际的生物体的类型取决于植物分泌物的数量和类型。在目前的项目中，我们建议阐明植物基因参与确定的数量和类型的基质失去了根沉积物，和植物发育的分泌物的反应。植物散发出非常多样化的有机分子集合，我们将利用尖端的质谱技术首次了解根沉积物的全部复杂性和组成。此外，我们将使用新出现的高通量测序技术来分析根中表达的基因及其与根沉积物释放的关系。此外，我们将调查的方式，改变根沉积物的组成影响的多样性和组成的微生物栖息在根际，并调查这些社区的功能是如何受到不同的渗出物的质量和数量。土壤微生物群落非常丰富和多样，我们将使用最新的高通量测序技术对微生物宏基因组进行测序，使我们能够同时研究根际发生的所有主要过程以及所涉及的群落的特定组成部分。此外，我们还将确定根际沉积对作物产量的影响，这将首次直接量化植物从根际沉积中获得的益处。这项工作将为培育新的作物品种开辟令人兴奋的可能性，其中根沉积被管理以提高作物产量，提高农业可持续性并减少对环境有害的投入。这项工作可以导致基因的鉴定，这些基因可以用于育种计划的许多应用，例如1。减少根际沉积可增加碳在地上部的分配，从而提高作物产量。2.管理根沉积物的数量和数量，可用于定制渗出，以促进溶解和吸收的生长限制养分，如P，S，K和微量金属，并增加耐受性有害的土壤金属，特别是铝3。根际沉积物的质量和数量可以被管理，以工程师在根际特定的微生物群落。这可能有许多优点，例如抑制降低作物生长的土壤传播病原体的生长，并刺激社区，提高作物生长限制营养素如P和N的可用性。

Plants use photosynthesis to fix CO2 to sugars, which are used for plant growth and development. Up to 50 % of carbon (C) fixed by plants is moved to roots, where it supports growth of root systems through the soil, in order to take up nutrients and water and drive growth. Healthy growing roots pass a large proportion of the C they receive to the soil as 'rhizodeposits'. This includes a range of materials, but soluble exudates, consisting of organic acids (e.g. citric acid), carbohydrates (e.g. glucose) and amino acids (e.g. leucine) comprise the largest rhizodeposit component. The total amount of rhizodeposits, and the specific types lost from roots, vary between plant species and genotypes within species, and is influenced by plant developmental stage and environmental parameters. Because of rhizodeposition and the presence of readily available C, the soil surrounding roots has large populations of microbes, forming a distinct microbial niche, which is termed the rhizoshere. Rhizosphere inhabiting microbes interact with plants in many ways- some are pathogens or beneficial symbionts, and others are involved in cycling and transformation of crop nutrients such as nitrogen (N) and phosphorus (P), altering their availability to plants. These processes determine plant productivity even in agricultural systems in which fertilisers are added to maximise production. The types of organisms which grow in the rhizosphere are determined by the amount and types of materials plants exude. In the current project we propose to elucidate plant genes involved in determining the amount and types of substrates lost from roots as rhizodeposits, and the response of exudation to plant development. Plants exude a very diverse collection of organic molecules and we will take advantage of cutting edge mass spectrometry techniques to understand the full complexity and composition of rhizodeposits for the first time. Additionally we will use newly emerging high throughput sequencing techniques to profile the genes expressed in roots and their association with release of rhizodeposits. Furthermore we will investigate the way in which altering the composition of rhizodeposits influences the diversity and composition of microbes inhabiting the rhizosphere, and investigate how the function of these communities is influenced by varying exudate quality and quantity. Soil microbial communities are incredibly abundant and diverse, and we will use the latest high throughput sequencing techniques to characterise the microbial metagenome, allowing us to investigate all the major processes taking place in the rhizosphere simultaneously and the specific components of the community involved. Furthermore we will determine the consequences of rhizodeposition for crop yield, which will provide the first direct quantification of the benefit plants receive from rhizodeposition. The work will open exciting possibilities to breed new crop varieties in which rhizodeposition is managed to enhance crop yields, increase agricultural sustainability and reduce environmentally damaging inputs. This work could lead to the identification of genes which could be used in breeding programmes for a number of applications, for example 1. Reduction of rhizodeposition could be used to increase C allocated to above ground growth, so that crop yields are enhanced. 2.Managing rhizodeposit quantity and quantity could be used to tailor exudation to promote solubilisation and uptake of growth limiting nutrients such as P, S, K and trace metals, and increase tolerance to harmful soil metals, particularly aluminium 3. The quality and quantity of rhizodeposits could be managed to engineer specific microbial communities in the rhizosphere. This could have many advantages, for instance inhibiting the growth of soil-borne pathogens which reduce crop growth, and stimulating communities which enhance the availability of crop growth limiting nutrients, such as P and N.