Metabolomics to elucidate the mechanisms of resistance in plants against biotic stress

植物对病原菌攻击的抗性可以是完全的(垂直的或主要是单基因的)，也可以是部分的(水平的或主要是多基因的)。后者由于数量遗传和缺乏合适的筛选基因类型的工具，没有被育种者很好地利用来进行生物胁迫管理。然而，代谢组学的最新发展呈现出光明的前景。真正的抗性机制从结构和生化两个方面进行了探索。在分子/代谢水平上了解植物的防御机制可能会导致新的策略来管理破坏性的作物病害。代谢组学是一个不断发展的系统生物学领域，它可以揭示基因的功能，而且代谢物往往是植物抵御逆境的最终产物，因此它也可以独立用于筛选抗性。用气相色谱-质谱法(GC/MS)鉴定了200多种抗性相关(RR)代谢产物(抗性的丰度高于敏感的)。然而，GC/MS只检测挥发性物质，对于非挥发性代谢物，需要使用高精度的质量色谱和质谱仪(LC/MS)。本研究的目的是利用LC/MS技术更好地了解小麦对赤霉病的抗性机制。本研究将建立小麦代谢组学数据库。通过代谢谱分析、接种抗性基因型的小穗及其丰度的多变量分析来鉴定RR代谢物，将研究抗性入侵的机制。通过分解毒素(DON)，通过接种产生和不产生DON的病原菌菌株的抗性基因型的代谢谱，以及根据不同生长阶段的轴节的代谢谱，研究病原菌在穗部内传播的抗性机制。本文所建立的小麦对赤霉病抗性机理的知识库，将被用来开发高通量的代谢组学技术，用于小麦抗赤霉病育种系的筛选。

Resistance in plants against pathogen attack can be complete (vertical or mainly monogenic) or partial (horizontal or mainly polygenic). The latter, because of quantitative inheritance and for lack of suitable tools to screen genotypes, is not well exploited by breeders for biotic stress management. However, the latest developments in metabolomics present a bright future. The mechanisms of true resistance are groped into structural or biochemical. Understanding of plant defense mechanisms at the molecular/metabolic level could lead to novel strategies to manage destructive crop diseases. Metabolomics is an evolving field of systems biology that can shed some light on the functions of genes, and furthermore, metabolites are often the end products of plant defense against stresses, thus it can also be used independently to screen for resistance. Using gas chromatography and mass spectrometry (GC/MS) we have identified more than 200 resistance related (RR) metabolites (higher abundance in resistant than in susceptible). However, GC/MS detects only volatiles and for non-volatile metabolites the use of high accurate mass liquid chromatography and mass spectrometry (LC/MS) is needed. The objective of the present study is to use LC/MS to better understand the mechanisms of resistance in wheat to fusarium head blight (FHB, Fusarium graminearum). In this study a wheat metabolome database will be established. The mechanisms of resistance to invasion will be investigated by metabolic profiling inoculated spikelets of resistant genotypes and multivariate analyses of their abundances to identify RR metabolites. The mechanisms of resistance to spread of pathogen within spike, through degradation of toxin (DON), will be investigated by metabolic profiling of resistant genotypes inoculated with pathogen strains producing and non-producing DON, and through containment of pathogen within rachis nodes based on metabolic profiles of rachis nodes at different growth stages. The knowledgebase generated here on the mechanisms of resistance in wheat to FHB, the biomarker RR metabolites identified, will be exploited to develop a high throughput metabolomics technology for screening wheat breeding lines for resistance to FHB.