钩藤花序梗败育机理研究

Uncaria rhynchophylla is one of the most commonly used traditional Chinese medicines, which the main medical parts are the branches bearing hook growing in the leaf axil. The branches bearing double hooks have both the highest medicinal and market value. However, we found that the hooks showed the arrangement of double hooks - single hook on the branches. The hooks and the peduncles of U. rhynchophylla are homologous floral organs, which develop the hooks on the vegetative branches but develop the complete inflorescences on the reproductive branches. There are the great negative effects of the formation of the single hook and the inflorescences on the yield of the double hooks. Therefore, the formation and the development of the peduncles are closely related to the yield and the quality of U. rhynchophylla. It is very important for the formation of the double hooks that promoting the differentiation of inflorescence meristem but inhibiting the differentiation of flower meristem based on the cognition of the floral formation process. In this project, the abortive and the fertile peduncles of the single hook and the double hooks during the different development period will be used as research materials. We aim to determine the mode and the key period of abortion by observing the (ultra) microstructures of different hook types, to reveal the regulation progress of abortion by analyzing the changes of the physiological-biochemical factors in the development process of the peduncles, to excavate the key genes of abortion by performing transcriptome sequencing. Finally, such information is very important in elucidating the formation and the development mechanism of the abortive peduncles (branches bearing hook), the main medicinal parts of U. rhynchophylla from the cellular, the physiological-biochemical and the molecular levels. This project not only provides the theoretical basis for breeding new varieties with high yield and good quality but also provides scientific guidance for the research on the formation and the development mechanism of the medicinal parts of other medicinal plants.

钩藤是我国常用大宗中药材，其主要药用部位为叶腋处的茎钩，以双钩型茎钩的药用和市场价值最高。但茎钩在枝条上以“双钩型-单钩型”依次排列。茎钩与花序梗为同源器官，营养枝条上为败育花序梗形成茎钩，生殖枝条上为可育花序梗形成完整花序。单钩型茎钩和完整花序的形成对双钩型茎钩产量造成不利影响，因此，钩藤花序梗的形成和发育与药材的产量和品质密切相关。基于植物成花过程的认知，促进花序分生组织分化，抑制花分生组织分化是形成双钩型茎钩的关键。本项目以不同发育时期的双钩型、单钩型败育和可育的钩藤花序梗为研究对象，观察其（超）显微结构确定败育方式和时期；分析其生理生化变化揭示败育调控过程；开展其转录组测序挖掘败育关键基因。从细胞形态、生理生化、分子水平综合阐述钩藤主要药用部位败育花序梗（茎钩）的形成与发育机理。不仅为钩藤高产优质新品种的选育提供理论支撑，也将对其他药用植物药用部位的形成与发育机理研究提供科学依据。

钩藤是我国常用大宗中药材，其主要药用部位为叶腋处的茎钩，然而茎钩与花序梗为同源器官，营养枝条上为败育花序梗形成茎钩，生殖枝条上为可育花序梗形成完整花序，花序的形成对钩藤药用部位的产量造成不利影响，因此，钩藤花序梗的形成和发育与药材的产量和品质密切相关。本项目以茎钩和花序梗为研究对象，观察二者的细胞形态结构上的异同点，揭示了植物激素在二者生长发育过程的作用，并应用转录组测序技术挖掘了二者生长发育过程的差异表达基因，从细胞形态、生理生化、分子水平综合阐述钩藤主要药用部位茎钩的形成与发育机理。本项目首先比较了茎钩和花序梗的形态和显微结构特征，发现二者之间虽略有差异，但也具有一定的相关性。茎钩和花序梗均可明显分为表皮、皮层和维管柱，各维管束之间具有相连成环的纤维，说明二者与茎结构相似，起源同一组织，可能属于同源器官。其次本项目选取三个不同发育时期的钩藤茎钩和花序梗为研究对象，测定二者在发育过程中植物内源激素及其合成前体的水平，并开展激素之间的相关性分析和互作网络化分析。研究结果表明，细胞分裂素类激素可能对钩藤成花形成具有促进并维持的作用，而对于钩藤而言，赤霉素类激素可能属于抑花激素，脱落酸促进钩藤花器官后期的衰老和脱落。同时，本项目也对三个不同发育时期的钩藤茎钩和花序梗进行了比较转录谱分析。研究结果表明，茎钩和花序梗在糖代谢、关键激素合成和信号传导等方面存在很大差异，表明糖代谢和内源激素是影响钩藤茎钩和花序梗发育的主要因素。此外，本项目为探索钩藤单钩形成机制，比较了钩藤单钩的叶腋茎段的下侧和上侧基因的差异表达情况。研究结果表明，钩藤单钩茎的上下侧的生长素梯度的建立和维持可能是钩藤叶腋单钩形成的关键作用之一。综上所述，本项目从多个水平综合阐明钩藤茎钩和花序的形成与发育机理，可为钩藤实际生产和品种选育奠定研究基础。