Browning D D, Lewis K E, O'Day D H
Department of Zoology, Erindale College, University of Toronto, Mississauga, Ont., Canada.
Biochem Cell Biol. 1992 Oct-Nov;70(10-11):1200-8. doi: 10.1139/o92-166.
Sexual development in Dictyostelium discoideum has many unique features making it an attractive eukaryotic model system for the study of biomembrane fusion and intercellular communication. The work presented here provides primary biochemical evidence for two distinct phases during early sexual development that appear to be defined by calcium-dependent gamete cell fusion. In addition, we introduce a novel procedure for the enrichment of zygote giant cells and use this method to define certain wheat-germ agglutinin binding glycoproteins which are specifically located in zygote giant cells and others which are markers for surrounding amoebae in the second phase of development. In addition, a G protein which is present in high amounts early in development is unique to giant cells in the second phase, suggesting a role in phagocytosis. Finally, alkaline phosphatase activity was found to mark the first phase of sexual development, suggesting a role in cell fusion. This contrasts with the patterns of alpha-mannosidase and beta-glucosidase activity that increase late in the second developmental phase, where they likely function in endocyte digestion during the cytophagic period. The developmental significance of these findings is discussed.
盘基网柄菌的有性发育具有许多独特特征，使其成为研究生物膜融合和细胞间通讯的极具吸引力的真核模型系统。本文所呈现的工作为早期有性发育过程中的两个不同阶段提供了初步的生化证据，这两个阶段似乎由钙依赖性配子细胞融合所界定。此外，我们引入了一种富集合子巨细胞的新方法，并利用该方法确定了某些小麦胚芽凝集素结合糖蛋白，它们特异性地位于合子巨细胞中，还有一些是发育第二阶段周围变形虫的标志物。另外，一种在发育早期大量存在的G蛋白在第二阶段是巨细胞所特有的，表明其在吞噬作用中发挥作用。最后，发现碱性磷酸酶活性标志着有性发育的第一阶段，表明其在细胞融合中发挥作用。这与α-甘露糖苷酶和β-葡萄糖苷酶活性的模式形成对比，它们在发育第二阶段后期增加，可能在吞噬期的内细胞消化中发挥作用。讨论了这些发现的发育意义。
