Unravelling the barley genetic control of the rhizosphere microbiota

近年来，越来越明显的是，植物和动物不是自主的生物体，而是由无数不同的微生物（统称为微生物群）定殖的。例如，一克紧紧附着在植物根部的土壤，称为根际，承载着数百万种不同的细菌。我们想了解植物是如何与根际的细菌交流的。这是一个关键的研究领域，因为根际细菌可以促进植物从土壤中吸收矿物质，保护植物免受疾病的侵害。然而，其他根际细菌可能是致病性的，并导致产量损失。了解这种通讯的分子基础意味着我们将能够为了植物的利益而重新连接它。最终，这可以帮助农民获得有利可图的产量，同时减少农用化学品对环境的投入和负面影响。在这个项目中，我们将使用作物大麦，这是全球第四大种植谷物，主要用于动物饲养以及酿造和蒸馏过程。我们以前证明了，通过现代育种选择的对化学输入做出反应的栽培“精英”品种，以及在边缘土地上进化的野生大麦植物，都有不同的微生物。我们还证明了塑造微生物群的能力是由大麦基因组中的基因编码的。我们最近发现，其中一些基因位于基因组的特定部分，科学家称之为基因座。在这里，我们想通过追求以下目标来进一步研究这种生物学现象。找出形成根际微生物的基因我们将利用遗传学的力量来研究数千种植物，这些植物是由一种优良的大麦品种和一种野生祖先杂交而成的。我们将使用非常强大的工具来跟踪这些后代植物中所有大麦基因组中基因的自然版本（称为等位基因）的独立遗传。通过研究来自大麦基因组的所有等位基因与每种植物支持的微生物群组成之间的相关性强度，我们将能够识别形成根际微生物群的实际基因。了解这些基因在分子水平上是如何工作的。植物释放大量分子到土壤中与细菌相互作用。我们将研究这些分子是否在精英大麦和野生大麦之间存在差异。同样，我们将研究根的性质，如它们的重量和长度，因为这些影响根探索土壤和与细菌相互作用的方式。最后，我们将确定有多少其他大麦基因表达的根之间的差异调节相同的线对，不同的基因组上的位点，支持不同的根际微生物群。总之，这将提供由我们正在研究的可能影响根际微生物增殖的位点调节的生物过程的图片。了解这些基因是否以及何时促进作物产量。我们将测试携带野生大麦基因座的优良材料是否会产生更多的谷物。我们将测试两种类型的土壤。在一种类型中，我们将模仿当前的农艺实践，并为植物提供化学肥料。在另一种类型中，我们将省略氮，一种主要的植物营养素。由于细菌在土壤中的氮循环中起着至关重要的作用，我们的假设是，野生大麦基因招募的细菌将为在有限供应下生长的植物提供优势。无论这是否会被证明，我们的研究结果将提供关于植物如何与根际细菌交流的关键信息。

In recent years it has become increasingly evident that plants and animals are not autonomous organisms but rather they are colonised by a myriad of different microorganisms, collectively referred to as the microbiota. For example, a single gram of soil tightly adhering to plant roots, and called rhizosphere, host millions of different bacteria. We want to understand how plants communicate with bacteria in the rhizosphere. This is a key area of research because bacteria in the rhizosphere can promote plant mineral uptake from soil and protect plants from diseases. However, other rhizosphere bacteria can be pathogenic and cause yield losses. Understanding the molecular basis of this communication means that we would be in the position to rewire it for the benefit of plants. Ultimately, this can help farmers to achieve profitable yields while reducing the input, and the negative impact, of agrochemicals in the environment. In this project we will use the crop plant barley, the fourth most cultivated cereal worldwide used mainly for animal feeding and in the processes of brewing and distilling. We previously demonstrated that cultivated 'elite' varieties, selected by modern breeding to respond to chemical inputs, and wild barley plants, which have evolved in marginal lands, host distinct microbiotas. We also demonstrated that the capacity to shape the microbiota is encoded by genes in the barley genome. We recently found out that some of these genes reside in a specific portion of the genome, which scientists call a locus. Here we want to investigate this biological phenomenon further by pursuing the following objectives.1. Find out the genes shaping the rhizosphere microbiotaWe will use the power of genetics to study thousands of plants derived from a cross between an elite barley variety and a wild ancestor. We will use fantastically powerful tools for following the independent inheritance of natural versions of genes (called alleles) from all over the barley genome in each of these progeny plants. By investigating the strength of correlation between alleles from all over the barley genome and microbiota composition supported by each of the plants we will be able to identify the actual gene(s) that shape the rhizosphere microbiota.2. Find out how these genes work at the molecular level.Plants release a lot of molecules into the soil to interact with bacteria. We will investigate whether these molecules differ between elite and wild barleys. Likewise, we will study properties of the roots, such as their weight and length, since these influence the way roots explore the soil and interact with bacteria. Finally, we will determine how many other barley genes expressed in the roots are differentially regulated between identical pairs of lines that differ only at the locus on the genome that supports different populations of rhizosphere microbiota. Together, this will provide a picture of the biological processes modulated by the locus we are investigating which may influence microbial proliferation in the rhizosphere.3. Find out if and when these genes promote crop yield. We will test whether elite material carrying the wild barley locus will produce more grain. We will test two types of soil. In one type, we will mimic current agronomic practices and plants will be provided with chemical fertilisers. In another type, we will omit nitrogen, a major plant nutrient. Owing to the fact that bacteria play a crucial role in recycling nitrogen in soil, our hypothesis is that bacteria recruited by wild barley genes will provide an advantage to plants grown under limiting supplies. Whether or not this will be proved, our results will provide key information on how plants communicate with bacteria in the rhizosphere.