Molecular Evolution of Pyrrolizidine Alkaloid Biosynthesis in the Tribe Crotalarieae (Fabaceae)

吡咯里西啶生物碱（Pyrrolizidine alkaloids，PAs）是植物在抵抗食草动物时产生的一类毒素。它们存在于被子植物的各个不相关的科中。对PA生物合成的第一个特异性酶--高培脒合酶（HSS）的研究表明，PA生物合成在被子植物进化过程中经历了多次独立的进化。这些谱系之一是豆科（豆科），开花植物的第三大家族，其中只有两个属被描述为包含PA生产物种：猪屎豆属和Lotononis。最近，我们已经能够表明，PA的生物合成，至少在猪屎豆，依赖于与根瘤菌共生。因此，猪屎豆属及其近缘种是研究生物碱生物合成与合成之间联系的生理和进化的独特系统。在这个项目中，我们将研究PA生物合成的定位和调控，并将此数据与相关植物产生喹哪里西啶生物碱（QA）的数据进行比较。分析的生物碱配置文件和序列编码HSS和它的parabolic脱氧羟腐胺赖氨酸合酶将揭示在PA生物合成的演变中的Crotalarieae，一个性状，最有可能有它的起源在QA生产的祖先。

Pyrrolizidine alkaloids (PAs) are a group of toxins that are produced as part of the plants chemical defense against herbivores. They occur in various unrelated families of the Angiosperms. Studies on the first specific enzyme of PA biosynthesis, homospermidine synthase (HSS), suggest that PA biosynthesis evolved several times independently during angiosperm evolution. One of these lineages is the legume family (Fabaceae), the third largest family of flowering plants, in which only two genera are described to contain PA-producing species: Crotalaria and Lotononis. Recently, we have been able to show that PA biosynthesis is, at least in Crotalaria, dependent on symbiosis with Rhizobia. Therefore, Crotalaria and related species are a unique system to study the physiology and evolution of this link between nodulation and alkaloid biosynthesis. In this project we will study the localization and regulation of PA biosynthesis and will compare this data with that of related plants producing quinolizidine alkaloids (QAs). Analyses of alkaloid profiles and sequences encoding HSS and its paralogue deoxyhypusine synthase will shed light in the evolution of PA biosynthesis in the Crotalarieae, a trait that most likely has its origin in QA-producing ancestors.