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

地衣的一个特点是产生多种次生代谢物，是一种共生关系。我们最近的研究表明，在渗透胁迫条件下，地衣分枝菌的培养具有产生某些地衣物质或新的代谢物的能力。指出地衣分枝菌培养物可作为生物活性化合物的新来源，也是研究地衣共生机制的良好工具。我们培养了在菲律宾、美国和日本收集的几种地衣的孢子衍生分枝真菌，并从其培养物中分离出多种化合物。培养的石墨属地衣分枝菌产生异coumarine、coumarine、色素、γ-内酯、二羧酸和苯基醚。毛孢拉玛林娜分枝菌落产生了一种新的氮蚜酮衍生物，并与脂肪酸、脂质和茴香酸结合。此外，培养的Lecanora sp.分枝菌产生了二苯并呋喃、萘吡喃和异苯并呋喃，而培养的Pyrenula sp.分枝菌产生了一种萘吡喃。令人感兴趣的是，地衣菌体能够产生在地衣化状态下从未检测到但与真菌代谢产物结构相关的物质，并且从培养的真菌中分离出的γ-内酯和二羧酸可以被认为是几种天然地衣物质的原型。从进化的观点来看，地衣的分枝体似乎保存了共生前时代自由生活真菌的次生代谢。也就是说，分离出来的支原体与自由生活的真菌（如Alternaria）的起源是相同的，它们获得了不同的生活方式，在进化过程中被分离。在与光生菌共生的状态下，菌体可能保留了古代菌体原有的代谢能力。这些代谢途径通常可能被光生物的任何作用所抑制，但在分离的菌体中表达。对培养的菌体次生代谢产物的进一步研究将为菌体在地衣中的进化和共生提供重要的信息。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