Urushihara H, Yanagisawa K
Institute of Biological Sciences, University of Tsukuba, Ibaraki, Japan.
Differentiation. 1987;35(3):176-80. doi: 10.1111/j.1432-0436.1987.tb00166.x.
The sexual cycle of Dictyostelium discoideum is initiated by the fusion of cells that are of opposite mating types (e.g. NC4- and HM1-type cells). Cells grown in light on agar plates are not capable of sexual cell fusion, but become capable when cultured in the dark in a liquid medium. Cells in the incapable state are called fusion-incompetent cells, and cells in the latter state, fusion-competent cells. To gain some understanding of the mechanism of cell fusion, cell ghosts prepared by freeze-thawing intact cells were incubated with intact cells. The cell ghosts killed the intact cells by directly fusing with them, the extent of fusion depending on the particular strains employed and the fusion-competency of the intact cells and of the cells from which the cell ghosts had been prepared. A detailed examination revealed that fusion-competent NC4 cells were always more easily killed by cell ghosts than fusion-incompetent NC4 cells. It also became apparent that cell ghosts prepared from fusion-competent NC4 cells killed all cell types far more efficiently than did those prepared from fusion-incompetent NC4 cells. However, fusion-competent and fusion-incompetent HM1 cells were equally sensitive to cell ghosts, and cell ghosts prepared from fusion-competent HM1 cells had the same ability to kill as those prepared from fusion-incompetent HM1 cells. From these findings, it thus appears that opposite mating-type cells have distinct membrane properties related to sexual cell fusion.
盘基网柄菌的有性周期由不同交配型细胞（如NC4型和HM1型细胞）的融合启动。在琼脂平板上光照条件下生长的细胞不能进行有性细胞融合，但在黑暗中液体培养基中培养时则具备这种能力。处于无融合能力状态的细胞称为融合无能细胞，而处于后一种状态的细胞称为融合有能细胞。为了深入了解细胞融合机制，将通过冻融完整细胞制备的细胞空壳与完整细胞一起孵育。细胞空壳通过与完整细胞直接融合将其杀死，融合程度取决于所使用的特定菌株以及完整细胞和制备细胞空壳的细胞的融合能力。详细检查发现，融合有能的NC4细胞总是比融合无能的NC4细胞更容易被细胞空壳杀死。同样明显的是，由融合有能的NC4细胞制备的细胞空壳比由融合无能的NC4细胞制备的细胞空壳更有效地杀死所有细胞类型。然而，融合有能和融合无能的HM1细胞对细胞空壳同样敏感，由融合有能的HM1细胞制备的细胞空壳与由融合无能的HM1细胞制备的细胞空壳具有相同的杀伤能力。从这些发现来看，不同交配型细胞似乎具有与有性细胞融合相关的独特膜特性。
