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

吡咯lizidine alkaloids （PAs）是一组毒素，作为植物对食草动物化学防御的一部分而产生。它们出现在被子植物的不同科中。对PA生物合成的第一个特异性酶——同亚精胺合成酶（HSS）的研究表明，PA生物合成在被子植物进化过程中独立进化了几次。其中一个谱系是豆科（豆科），这是开花植物的第三大科，其中只有两个属被描述含有产生pa的物种：Crotalaria和Lotononis。最近，我们已经能够证明，至少在Crotalaria中，PA的生物合成依赖于与根瘤菌的共生。因此，Crotalaria及其近缘种是研究结瘤与生物碱生物合成这一联系的生理和进化的独特系统。在本项目中，我们将研究PA生物合成的定位和调控，并将这些数据与产生喹诺齐啶生物碱（QAs）的相关植物的数据进行比较。分析编码HSS及其旁联脱氧碱基合成酶的生物碱谱和序列，将有助于揭示crotalaria科PA生物合成的进化过程，这一特征最有可能起源于产生qa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.