Unraveling rice - endophyte interactions: Genome-wide analyses of the endophytic lifestyle of the diazotroph Azoarcus sp. strain BH72

全球气候变化和化石燃料成本的增加要求世界范围内更可持续地利用农业资源，并促进发展需要尽可能少的石化投入的种植制度。内生细菌驻留在植物的活组织中，不会对其造成实质性的伤害。有益细菌和植物之间的内生联系对于农业生物技术的应用具有很高的兴趣，例如用于改善植物生长和健康，甚至作为生物肥料。尤其是大气氮素对粮食作物的补给是固氮草内生植物具有重要的农学和生态潜力。然而，需要更深入地了解内生菌如何与寄主植物相互作用。对不同根际和土壤中微生物群落的调查表明，内生根群落需要大量的细菌适应，比根面或根际土壤微生物群落更具专化性，多样性更低。结合有关细菌功能的知识，可以假设细菌在根内建立自己的过程是一个活跃的过程。由于植物细胞通常可以通过植物的天然免疫调节防御反应来检测细菌分子成分(MAMPs)并对其做出反应，内生菌能否在组织内大量建立是令人困惑的。在分子水平上研究细菌内生菌和单子叶植物的模式系统之一是无菌草(Azoarcus sp.)菌株BH72与水稻的互作。固氮藻Azoarcus sp.菌株BH72是禾本科牧草等牧草的固氮内生菌，能为寄主提供固氮。此外，水稻的根部也有很好的定植。由于这两个配对的基因组序列，水稻和固氮藻。菌株BH72是可用的，这两种生物都为功能基因组分析提供了一个很好的模型系统，以揭开最初的相互作用过程。基于前一个项目阶段的全局转录方法，我们的目标是进一步确定在水稻的定殖和生理上成功互作中起作用的细菌特性，从而揭示内生生活方式的机制。利用尖端技术，新的焦点将是反义RNA和新开发的在植物中进行单个细菌细胞基因表达定量的方法。

Global climate change and increasing costs of fossil fuels demand worldwide a more sustainable use of resources in agriculture and foster the development of cropping systems requiring least possible petrochemical input. Endophytic bacteria reside within the living tissue of a plant without substantively harming it. Endophytic associations between beneficial bacteria and plants are of high interest for agro-biotechnological applications, e.g. for improvement of plant growth and health, or even as biofertilizer. Especially the supply of atmospheric N2 to cereal crops is an agronomically and ecologically important potential of N2-fixing grass endophytes. However, a deeper understanding of how endophytes interact with their host plants is required. Surveys of microbial communities in different root and soil compartments suggest, that the endophytic root community requires numerous bacterial adaptations, is more specialized and less diverse that rhizoplane or rhizosphere soil microbiomes. Together with knowledge on bacterial functions, it can be assumed that it is an active process for bacteria to establish themselves inside the roots. As plant cells can commonly detect and react to bacterial molecular components (MAMPs) by the plant's innate immunity-regulated defense responses, it is puzzling that endophytes can establish in high numbers inside tissues.One of the best-studied model systems at the molecular level for bacterial endophytes and monocotyledonous plants is the Azoarcus sp. strain BH72 - rice interaction. Azoarcus sp. strain BH72 is a nitrogen-fixing endophyte of grasses such as Kallar grass and can contribute fixed nitrogen to its host. Also rice roots are colonized well. Since genome sequences of both partners, Oryza sativa (rice) and Azoarcus sp. strain BH72 are available, both organisms provide an excellent model system for functional genomic analyses to unravel initial interaction processes. Based on the global transcriptomic approach of the previous project phase, we aim to further identify bacterial characteristics that play a role in colonization and physiologically successful interaction with rice, and thus to unravel mechanisms of the endophytic lifestyle. Using cutting-edge technology, new foci will be on antisense RNA and newly developed approaches for single bacterial cell gene expression quantification in planta.