Investigating how plants recruit antibiotic-producing Streptomyces bacteria to protect themselves against disease

人类使用抗生素治疗疾病的历史不到100年，但它们在自然界的使用可追溯到数千万年前。我们使用的大多数抗生素都是由一组称为链霉菌的常见土壤细菌制成的，植物和昆虫早在人类之前就开始使用它们。植物包括模式拟南芥和重要的粮食作物，如小麦，马铃薯和水稻，都有链霉菌生活在他们的根。事实上，最近几篇备受瞩目的论文表明，链霉菌细菌在根际（覆盖根部的土壤）中富集，与周围土壤相比，在拟南芥的根内富集程度更高。2015年8月发表在《科学》杂志上的一项研究表明，链霉菌细菌特别被植物产生的水杨酸（SA）吸引，水杨酸是它们一般应激反应的一部分。这表明链霉菌（但不是所有细菌）可以使用SA作为食物来源，因此植物可以从土壤中存在的数万亿细菌中特异性地选择对它们有用的细菌。由这些链霉菌菌株产生的抗生素被认为可以保护植物根部免受真菌感染。在这个项目中，我们将使用拟南芥作为一个模型来测试（1）如果链霉菌细菌在根际和根真的使用植物产生的SA作为食物，（2）如果任何和所有的链霉菌菌株可以生活在植物根内，（3）如果SA代谢是必不可少的根殖民链霉菌和（4）如果链霉菌产生的抗真菌剂确实保护植物免受真菌感染。最终，这项工作将为工程改良链霉菌菌株用于农业奠定基础，从而为全球粮食安全做出贡献。

Humans have been using antibiotics to treat disease for less than 100 years but their use in nature stretches back for tens of millions of years. Most of the antibiotics we use are made by a group of common soil bacteria called Streptomyces and plants and insects started using them long before humans. Plants including the model Arabidopsis thaliana and important food crops like wheat, potato and rice, all have Streptomyces living inside their roots. Indeed, several recent high profile papers have shown that Streptomyces bacteria are enriched in the rhizosphere (the soil coating the roots) and even more greatly enriched inside the roots of Arabidopsis compared to the surrounding soil. Research published in Science in August 2015 suggests that Streptomyces bacteria are specifically attracted by salicylic acid (SA) that is produced by the plants as part of their general stress response. The suggestion is that Streptomyces (but not all bacteria) can use SA as a food source and thus the plants can specifically select bacteria that are useful to them out of the trillions of bacteria present in the soil. The antibiotics made by these Streptomyces strains are thought to protect the plant roots against fungal infection. In this project we will use Arabidopsis as a model to test (1) if Streptomyces bacteria in the rhizosphere and roots are really using plant-produced SA as food, (2) if any and all Streptomyces strains can live inside plant roots, (3) if SA metabolism is essential for root colonisation by Streptomyces and (4) if Streptomyces-produced antifungals do indeed protect the plants against fungal infection. Ultimately this work will lay the foundation for engineering improved Streptomyces strains for use in agriculture and thus contribute to global food security.