Studies on the production by the cultures of isolated lichen mycobionts and symbiosis in the lichen

地衣是一种共生体，其特征之一是产生多种次级代谢产物。我们最近的研究表明，培养的地衣菌有能力在逆境条件下产生某些地衣物质或新的代谢产物。指出地衣共生菌的培养是地衣中生物活性物质的新来源，也是研究地衣共生机制的良好工具。我们培养了从菲律宾、美国或日本采集的几种地衣孢子衍生的真菌，并从它们的培养物中分离出不同的化合物。培养的葡萄属地衣菌产生异香豆素、香豆素、色酮、γ-内酯、二羧酸和苯基醚。利用该菌产生一种新的氮杂萘酮衍生物，该衍生物与脂肪酸、脂类和松萝酸一起产生沿着。此外，培养的蜡蚧属真菌。产生了二苯并呋喃，萘并吡喃和异香豆素 关于我们 培养的核壳菌（Pyrenula sp.）产生了另一种萘并吡喃，地衣菌能产生一些在地衣化状态下从未检测到的物质，但它们在结构上与真菌代谢物有关，从培养的核壳菌中分离的γ-内酯和二羧酸可被认为是几种天然地衣物质的原型。从进化的角度来看，地衣中的真菌在共生前时期似乎保存了自由生活真菌的次生代谢。也就是说，分离的真菌生物与自由生活的真菌（如链格孢属）的起源相同，但它们在进化过程中获得了不同的生活方式并被分离。在与光合菌共生的状态下，真菌可能保存了古真菌原有的代谢能力。这些代谢途径通常可能被光合生物的任何作用抑制，但在分离的真菌中表达。进一步研究地衣真菌的次生代谢产物，将为地衣真菌的进化和地衣共生提供重要信息。少

One characteristic of lichens, a symbiotic association, is the production of diverse secondary metabolites. Our recent studies demonstrated that cultures of lichen mycobionts have an ability under osmotically stressed conditions to produce certain lichen substances or novel metabolites. It was pointed out that cultures of lichen mycobionts could be new sources of bioactive compounds and also good tools for investigating the symbiotic mechanism in lichens. We cultivated the spore-derived mycobionts of several species of lichens collected in Philippines, U.S.A.or Japan, and isolated diverse compounds from their cultures. The cultured lichen mycobionts of the genus Graphis yielded isocoumarines, coumarine, chromones, γ-lactones, dicarboxylic acids, and phenyl ethers. Mycobionts of Ramalina otenospora produced a new azaphilone derivative along with fatty acids, lipids and usnic acid. Furthermore, the cultured mycobionts of Lecanora spp. yielded dibenzofurans, a naphthopyran and an isocouma … More rine, while the cultured mycobionts of Pyrenula sp. yielded another naphthopyran.It is of great interest to know that lichen mycobionts are able to produce substances which have never been detected in the lichenized state but were structurally related to fungal metabolites and that γ-lactones and dicarboxylic acids isolated from the cultured mycobionts could be recognized as prototypes of several natural lichen substances. From the viewpoint of evolution, the mycobionts of the lichens seem to conserve the secondary metabolism of free-living fungi in the pre-symbiosis age. Namely, the origin of isolated mycobionts is the same as that of free-living fungi, for example, Alternaria, and they gained different lifestyles and were separated in the evolutional process. In symbiotic state with photobionts, the mycobionts might conserve the original metabolic ability of ancient mycobionts. These metabolic pathways might be normally supressed by any action of the photobiont, but expressed in the isolated mycobiont. Further studies on secondary metabolites form the cultured mycobionts will provide significant information on the evolution of mycobiont and symbiosis in the lichen. Less