Polyploidy underlies co-option and diversification of biosynthetic triterpene pathways in the apple tribe

背景+问题：Whole-genome duplication (WGD) plays important roles in plant evolution and function, yet little is known about how WGD underlies metabolic diversification of natural products that bear significant medicinal properties, especially in nonmodel trees. 

主要研究：Here, we reveal how WGD laid the foundation for co-option and differentiation of medicinally important ursane triterpene pathway duplicates, generating distinct chemotypes between species and between developmental stages in the apple tribe. 

结果1-两个苹果族物种的基因组：After generating chromosome-level assemblies of a widely cultivated loquat variety and Gillenia trifoliata, we define differentially evolved, duplicated gene pathways and date the WGD in the apple tribe at 13.5 to 27.1 Mya, much more recent than previously thought. 

结果2-通路鉴定与功能验证：We then functionally characterize contrasting metabolic pathways responsible for major triterpene biosynthesis in G. trifoliata and loquat, which pre- and postdate the Maleae WGD, respectively. 

结论：Our work mechanistically details the metabolic diversity that arose post-WGD and provides insights into the genomic basis of medicinal properties of loquat, which has been used in both traditional and modern medicines.

 摘 要 

全基因组复制（WGD）在植物的演化和功能方面发挥重要的作用，但是关于WGD是如何影响具有重要药用价值的天然产物，尤其是非模式树木中的代谢物多样化还不清楚。本文中，作者揭示了苹果族植物中，具有重要药用价值的乌苏烷类三萜通路因为WGD发生了复制，从而导致该族不同植物物种之间和不同发育阶段形成了不同的化学型。作者通过组装了一个广泛栽培的枇杷品种和阔叶美吐根（Gillenia trifoliata），鉴定了差异演化的、复制的基因通路，并且将苹果族的WGD发生时间定位在了一千三百五十万年到两千七百一十万年前，这个时间点要比之前所认为的更加靠近现代一些。接着，作者对阔叶美吐根和枇杷中主要负责三萜化合物生物合成的代谢通路进行了功能验证，这两个通路一个形成于苹果族WGD之前，一个形成于苹果族WGD之后。本文的工作从机制上详细说明了WGD后产生的代谢多样性，并为已用于传统和现代制药的枇杷其药用特性潜在的基因组基础提供了见解。