Unravelling the barley genetic control of the rhizosphere microbiota

点击翻译按钮获取中文摘要

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.