Tsukamoto S, Kato H, Hirota H, Fusetani N
Fusetani Biofouling Project, Exploratory Research for Advanced Technology (ERATO), Research Development Corporation of Japan (JRDC), c/o Niigata Engineering Co., Ltd, Isogo-ku, Yokahama, Japan.
Eur J Biochem. 1999 Sep;264(3):785-9. doi: 10.1046/j.1432-1327.1999.00642.x.
It has long been known that metamorphosis of ascidian larvae is induced by exposure to adult tunic extract or larval-conditioned seawater. However, such a natural 'inducer' has not been identified, probably due to its very low concentration in organisms. Here we have succeeded in isolating the same metamorphosis-inducing substance from the larvae, the larval-conditioned seawater, and the adult tunic of the ascidian Halocynthia roretzi. Structural analysis revealed that this substance was identical to lumichrome. Lumichrome was active toward H. roretzi larvae, but inactive toward another ascidian larvae, suggesting that lumichrome is species-specific. Riboflavin (vitamin B2), from which lumichrome might be derived from, was found to be inactive in induction of larval metamorphosis. In addition, it was demonstrated that lumichrome is localized predominantly in the basal region of the adhesive organ and the posterior part of the larval trunk. Thus, we propose that lumichrome functions as a natural inducer for larval metamorphosis in H. roretzi. This is the first natural metamorphosis-inducing substance to be identified in ascidians.
长期以来已知，海鞘幼虫的变态是由暴露于成年海鞘被囊提取物或幼虫 conditioned 海水诱导的。然而，这种天然的“诱导物”尚未被鉴定出来，可能是由于其在生物体中的浓度非常低。在这里，我们成功地从海鞘 Halocynthia roretzi 的幼虫、幼虫 conditioned 海水和成年海鞘被囊中分离出了相同的变态诱导物质。结构分析表明，这种物质与光色素相同。光色素对 Halocynthia roretzi 幼虫有活性，但对另一种海鞘幼虫无活性，这表明光色素具有物种特异性。发现可能衍生出光色素的核黄素（维生素 B2）在诱导幼虫变态方面无活性。此外，还证明光色素主要定位于附着器官的基部区域和幼虫躯干的后部。因此，我们提出光色素作为 Halocynthia roretzi 幼虫变态的天然诱导物发挥作用。这是在海鞘中鉴定出的第一种天然变态诱导物质。
