Mechanisms for heartwood lignan biosynthesis

这项研究的最终目的是阐明心材苯丙素类化合物生物合成的分子机制。在本研究中，首席调查者和他的同事首先调查了钝顶叶树心材木脂素的可能前体，并鉴定了一个新的木脂素和9个已知的木脂素，其中一些可能是胡萝卜素的前体木脂素。此外，通过同时喂食实验，建立了另一种典型的心材木脂素的生物合成途径。这项技术也被发现在代谢组分析中非常有用。第二，在以前的论文中，主要研究者和同事报道了牛膝和维克斯特罗木脂素生物合成的立体化学机制与连翘不同。作为前人工作的继续，在本研究项目中，他们以牛至、瑞香、红掌和亚麻等几种植物为材料，研究了木脂素生物合成的立体化学机制。并认为松脂醇/落叶松脂醇还原酶多种异构体的空间分化和物种特异性表达至少部分解释了木脂素生物合成的立体化学多样性。其次，利用红花cDNA文库对几种参与木脂素生物合成的OMT进行了cDNA克隆，并成功地克隆了一些OMT的cDNA。利用重组酶对OMTs进行了表征。最后，对另一种重要的心材物质去甲木脂素的生物合成进行了研究。因此，首次建立了从苯丙烷类单体到去甲木脂素顺式胡萝卜素的生物合成途径。ρ-香豆基乙醇和ρ-香豆基CoA是去甲木脂素的直接C6-C3前体。此外，还首次检测到去甲木素合成酶活性。

The final goal of this research is to elucidate molecular mechanisms for biosynthesis of heartwood phenylpropanoid compounds.In the present study, firsty, the principal investigator and his coworkers surveyed possible precursors of a heartwood lignan, hinokinin, in Chamaecyparis obtusa, and identified a novel lignan together with 9 known lignans, some of which are probably precursor lignans of hinokinin. In addition, the biosynthetic pathway of another typical heartwood lignan, yatein, has been established by means of cimultaneous feeding experiments. The technique has also been found to be very useful for metabolome analyses.Secondly, in the pervious papers, the principal investigator and co-workers reported the stereochemical mechanisms in lignan biosynthesis in Arctium lappa and Wikstroemia sikokiana are different from that in Forsythia spp. As the continuation of the previous works, in this research project they studied the stereochemical mechanisms in lignan biosynthesis using several plant species including Arctium lappa, Daphne spp., Anthriscus sylvestris, and Linum flavum var. compactum, and concluded that spatially differentiated and species specific expression of multiple isoforms of pinoresinol/lariciresinol reductase can account, at least in part, the stereochemical diversity in lignan biosynthesis,Next, cDNA cloning of several OMTs which are involved in lignan biosynthesis was carried out using Carthamus tinctorius cDNA library, and some OMT cDNAs have been successfully cloned. Characterizaion of the OMTs using recombinant enzymes are under way.Lastly, biosynthesis of another important heartwood substance, norlignan, was studied. Thus, a biosynthetic pathway from phenylpropanoid monomers to a norlignan, cis-hinokiresinol, has been established for the first time. ρ-coumaryl alchol and ρ-Coumaryl CoA were found to be immediate C6-C3 precursors of the norlignan. Also, norlignan synthase activity has been detected for the first time.