Aiba K, Yanagisawa K, Urushihara H
University of Tsukuba, Institute of Biological Sciences, Ibaraki, Japan.
J Gen Microbiol. 1993 Feb;139(2):279-85. doi: 10.1099/00221287-139-2-279.
Sexual cell fusion occurs between NC4 and HM1, heterothallic strains of Dictyostelium discoideum. Several cell surface proteins relevant to the process have been identified. One of them, gp138, exists in fusion-competent cells of both NC4 and HM1, and is considered to be more concerned with membrane fusion than gamete recognition. In this study, we raised monoclonal antibodies against gp138 and examined gp138 distribution among strains and species of cellular slime moulds to confirm its importance in sexual cell fusion. All heterothallic and bisexual D. discoideum strains examined were found to possess gp138, while asexual and homothallic strains lacked it. The anti-gp138 monoclonal antibody detected several distinct proteins in homothallic strains and one in an asexual strain. Some of the former proteins appeared together with the increase in binucleated cells. Cells of Dictyostelium mucoroides and Polysphondylium pallidum did not possess proteins reactive to the monoclonal antibody. These results indicate that gp138 is common among, but restricted to, cross-matable strains of D. discoideum. Our results also support previously published molecular phylogenetic studies which suggest that homothallic and asexual strains of D. discoideum are remote from other strains of D. discoideum but are less distantly related to them than other species are.
性细胞融合发生在盘基网柄菌的异宗配合菌株NC4和HM1之间。已经鉴定出几种与该过程相关的细胞表面蛋白。其中一种，即gp138，存在于NC4和HM1的具备融合能力的细胞中，并且被认为与膜融合的关系比配子识别更为密切。在本研究中，我们制备了针对gp138的单克隆抗体，并检测了gp138在细胞黏菌的菌株和物种中的分布，以证实其在性细胞融合中的重要性。所有检测的异宗配合和双性的盘基网柄菌菌株都被发现含有gp138，而无性和同宗配合菌株则缺乏该蛋白。抗gp138单克隆抗体在同宗配合菌株中检测到几种不同的蛋白，在一个无性菌株中检测到一种蛋白。前者中的一些蛋白随着双核细胞数量的增加而一起出现。黏液盘基网柄菌和苍白聚孢黏菌的细胞不含有与单克隆抗体反应的蛋白。这些结果表明，gp138在盘基网柄菌的可杂交菌株中普遍存在，但仅限于这些菌株。我们的结果还支持了先前发表的分子系统发育研究，该研究表明，盘基网柄菌的同宗配合和无性菌株与盘基网柄菌的其他菌株距离较远，但与它们的亲缘关系比与其他物种的亲缘关系更近。
