Biosynthesis, transport and exudation of 1,4-benzoxazin-3-ones as determinants of plant biotic interactions

建立合适的生物生态位对植物生存和农业生产力至关重要。植物塑造环境的一个重要机制是释放植物化学物质。尤其是低分子化合物可以启动与土壤中有益微生物的相互作用，并阻止食草动物。然而，同样的信号分子也可能被专门的害虫和病原体利用。对它们的生物合成、运输和释放的详细了解对于理清这些看似相互矛盾的影响和在可持续种植系统中充分利用次生代谢物渗出的潜力至关重要。然而，到目前为止，在作物模型系统中还没有发现次生代谢物输出物。在这里，我们建议联合欧洲不同研究小组的专业知识来研究玉米1，4-苯并恶嗪-3-酮(BX)分泌的分子基础。该联盟成员以前的工作已经确定BXS是玉米和其他牧草的重要抗性因子，并详细阐明了它们的生物合成。我们还表明，BXS是玉米根分泌物和叶质外体中的主要次生代谢物，它们是有益微生物以及玉米最具破坏性的害虫之一--玉米根结线虫的重要补充信号。考虑到它们对作物生产力的明显重要性以及它们强烈参与细胞外信号传递，BXS是研究次生代谢物渗出的分子生态学的理想和相关的模型。BENZEX的总体目标是创建迄今为止在细胞外植物与环境相互作用方面最先进的分子工具包。首先，通过干扰或增强三种重要的生物合成酶的表达，将建立一个在BX生物合成中改变的玉米基因型的综合群体。第二个有针对性的和非有针对性的参考方法，以确定和量化BX的生产、储存、渗出和转化，将使用高效液相色谱-质谱仪和13C标记的BX前体建立。第三，BX转运体将通过蛋白质组学、定量聚合酶链式反应和植物化学指导的QTL定位相结合的方法进行鉴定。第四，所产生的资源将用于分析胞外BXS在与土壤微生物群、植物生长促进菌、丛枝菌根真菌、根部食草动物和食叶蚜虫相互作用中的作用。综上所述，我们的项目将大大增加关于次生代谢物渗出的生物学相关性的知识。它将进一步提高欧洲分子植物科学的竞争力，提供一系列新的工具和资源，包括转基因植物和突变体、分析方法以及作为重要农业模式系统的玉米的分子和微生物标记。

The establishment of a suitable biotic niche is essential for plant survival and agricultural productivity. One important mechanism by which plants shape their environment is the release of phytochemicals. Low molecular weight compounds in particular can initiate the interaction with beneficial microbes in the soil and ward off herbivores. However, the same signalling molecules may also be exploited by specialized pests and pathogens. A detailed understanding of their biosynthesis, transport and release will be essential to disentangle these seemingly contradicting effects and to harness the full potential of secondary metabolite exudation in sustainable cropping systems. Yet to date, no secondary metabolite exporters have been identified in crop model systems.Here we propose to unite the expertise of different research groups across Europe to study the molecular basis of 1,4-benzoxazin-3-one (BX) exudation in maize. Previous work by the consortium members has identified BXs as important resistance factors in maize and other grasses and has elucidated their biosynthesis in detail. We have also shown that BXs are the dominant secondary metabolites in maize root exudates and the leaf-apoplast and that they are important recruitment signals for beneficial microbes as well as for one of the most damaging pests of maize, the western corn rootworm Diabrotica virgifera. Given their obvious importance for crop productivity and their strong involvement in extracellular signalling, BXs are an ideal and relevant model to study the molecular ecology of secondary metabolite exudation. The overall aim of BENZEX is to create the most advanced molecular toolkit in extracellular plant-environment interactions to date. First, a comprehensive population of maize genotypes that are altered in BX biosynthesis will be established by interrupting or enhancing the expression of three important biosynthetic enzymes. Second targeted and untargeted reference methods to identify and quantify BX production, storage, exudation and transformation will be established using HPLC-MS and 13C-labelled BX precursors. Third, BX transporters will be identified by a combination of proteomics, quantitative PCR and phytochemically guided QTL-mapping. Fourth, the generated resources will be used to analyse the role of extracellular BXs in the interaction with the soil microbiome, plant growth promoting bacteria, arbuscular mycorrhizal fungi, root herbivores and leaf-feeding aphids. Taken together, our project will substantially increase knowledge about the biological relevance of secondary metabolite exudation. It will furthermore enhance the competitiveness of European molecular plant sciences by providing an array of new tools and resources, including transgenic plants and mutants, analytical methods as well as molecular and microbial markers for maize as an important agricultural model system.