Genetic Determinants of Microbiome Assembly on Plant Roots

植物根系对植物吸收矿物质养分至关重要。此外，它们还与土壤环境和细菌、真菌、单细胞动物细胞、线虫和其他生物的复杂组合相互作用。根周围被这些生物占据的区域被称为根际，这些生物的总称是根际微生物群。微生物也存在于植物的根内，通常在植物细胞之间，被称为内生菌。根际微生物群和内圈微生物群共同构成植物的根微生物群。在过去的几年里已经证明，根部微生物群对植物的健康和生长至关重要，许多微生物被证明是促进植物生长的。细菌是简单的单细胞微生物，缺乏植物和动物高等细胞中的膜结合结构。然而，尽管细菌可能没有那么复杂的细胞组织，但它们可以进行植物和动物所没有的大量化学反应。细菌负责许多营养物质的循环，如N2 （N2也被称为氮气，由两个氮原子由一个强大的三键结合而成），这是一种非常惰性的大气气体。氮气占大气的78%，但非常不活泼，不能直接用作氨基酸、蛋白质和DNA合成所需的氮的来源。然而，少数细菌可以将N2还原（加入氢）并将其转化为氨（NH3），氨很容易被包括细菌和植物在内的各种生物合成为氨基酸和所有其他构成生命的物质。其他细菌对植物获得磷酸盐至关重要，而氮是限制植物生长的两种主要营养物质。然而，我们现在意识到，细菌并不是单独工作的，而是作为一个复杂的群落工作的，也被称为微生物组，其中有数百甚至数千个成员相互作用，并与宿主植物相互作用。就像人类的肠道和身体一样，植物的健康和生长也会被细菌微生物群深刻地改变。最近的一个突破是，我们可以只用6到7个关键成员来研究微生物群是如何发展的，这简化了分析。在这个提议中，我们已经开发了跟踪7种细菌如何相互作用并研究潜在遗传原因的方法。这使我们能够超越对微生物群组成部分的简单描述，从而研究控制微生物群的遗传机制以及微生物群如何稳定地定植于植物根系。这项研究将导致农业关键作物（包括大麦和小麦等谷物）的植物微生物群特征的一个步骤变化。

Plant roots are critical for the uptake of mineral nutrients by plants. In addition, they interact with the soil environment and a complex assemblage of bacteria, fungi, single celled animal cells, nematodes and other organisms. The area directly around roots that is occupied by these organisms is known as the rhizosphere and the collective name for the organisms is the rhizosphere microbiota. Microorganisms also reside inside plant roots, usually between plant cells and are knows as endophytes. Together the rhizosphere and endosphere microbiotas makes up the root microbiota of a plant. It has been shown over the last few years that the root microbiota is critical for the health and growth of plants, with many microorganisms shown to be plant growth promoting. Bacteria are simple single celled microorganisms that lack the membrane bound structures found in higher cells of plants and animals. However, while bacteria may have a less complex cellular organisation they carry out a huge range of chemical reactions not found in plants and animals. Bacteria are responsible for the cycling of many nutrients such as N2 (N2 is also known as nitrogen gas and consists of two nitrogen atoms bound by a strong triple bond), which is a very inert atmospheric gas. N2 makes up 78% of the atmosphere but is very unreactive and cannot be used directly as a source of nitrogen, which is needed for amino acid, protein and DNA synthesis. However, a small number of bacteria can reduce (add hydrogen) to N2 and convert it into ammonia (NH3), which is readily incorporated into amino acids and then all the other building blocks of life, by a wide range of organisms including bacteria and plants. Other bacteria are crucial to make phosphate available to plants which with nitrogen are the two main nutrients limiting plant growth. However, we now realise that bacteria do not work alone but rather they work as complex communities, also known as a microbiome, with hundreds or even thousands of members interacting with each other and host plants. Just as for the human gut and body the health and growth of plants is profoundly altered by the bacterial microbiome. A recent breakthrough is the demonstration that we can study how microbiomes develop using just 6 or 7 key members which simplifies the analysis. In this proposal we have developed ways to track how 7 bacteria interact and to study the underlying genetic causes. This enables us to move beyond simple characterisation of the components of the microbiota to examine the genetic mechanisms of control and how a microbiome stably colonises plant roots. This research will lead to a step change in characterisation of plant microbiota of agriculturally critical crops, including cereals such as barley and wheat.