Control of gene expression in rhizosphere bacteria by plant metabolites

随着人口的不断增长，预计到2100年将达到110亿以上，农业必须能够相应增长，以维持这一人口规模。到目前为止，农业产量的增加一直依赖于哈伯博施工艺生产的含氮合成肥料。然而，这在环境和经济上都是不可持续的。在自然界中，生物固氮（BNF）是由原核生物使用固氮酶进行的。有限的一组植物能够与这些原核生物形成共生关系，使它们能够从生物固氮中受益。这方面研究最充分的例子是豆科植物和根瘤菌之间的共生。然而，小麦等主要谷类作物无法形成类似的共生关系，这意味着这些作物主要依赖哈伯-博斯氮。21世纪生物学研究的一个持续挑战是将生物固氮应用于主要谷类作物。该项目旨在通过将植物促生根际细菌（PGPR）的固氮和排泄与天然植物信号联系起来，将生物固氮扩展到谷物。将使用RNA测序、qRT-PCR和lux启动子融合来鉴定响应谷物根分泌物的细菌调节系统，并使用质谱来表征这些根分泌物。控制电路将被设计成将这些调控系统与编码固氮产物的基因联系起来，特别是调控基因nifA。这将导致工程菌株的形成，在谷物根际固定和排泄氮。

With a growing human population expected to reach over 11 billion by 2100, it is vital that agriculture is able to grow correspondingly to sustain this population size. To date, increases in agricultural yield have been supported by reliance on synthetic fertilisers containing nitrogen produced by the HaberBosch process. However, this is neither environmentally nor economically sustainable. In the natural world, biological nitrogen fixation (BNF) is carried out by prokaryotes using the enzyme nitrogenase. A limited group of plants is able to form symbiotic associations with these prokaryotes, allowing them to benefit from BNF. The most well-studied example of this is the symbiosis between legumes and rhizobia. However, staple cereal crops such as wheat are unable to form a similar symbiosis, meaning that these crops are primarily dependent on Haber-Bosch nitrogen. An ongoing challenge in biological research in the 21st century is that of applying BNF to staple cereal crops. This project aims to extend BNF to cereals by linking nitrogen fixation and excretion in plant growth-promoting rhizobacteria (PGPRs) to a natural plant signal. Bacterial regulatory systems that respond to cereal root exudates will be identified using RNA sequencing, qRT-PCR and lux promoter fusions, and these root exudates characterised using mass spectrometry. Control circuits will be engineered to link these regulatory systems to genes encoding products involved in nitrogen fixation; in particular, the regulatory gene nifA. This will result in the formation of engineered bacterial strains that fix and excrete nitrogen in cereal rhizospheres.