2. PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan.
3. Department of Biotechnology, College of Life Sciences, Ritsumeikan University, Nojihigashi, Kusatsu, Shiga 525-8577, Japan.
4. Department of Biological Sciences, Faculty of Science and Engineering, Ishinomaki Senshu University, Ishinomaki, Miyagi 986-0031, Japan.
5. Tohoku Medical Megabank Organization, 2-1 Seiryo-Machi Aoba-ku, Sendai 980-8574, Miyagi, Japan.
Background: Macrocyst is known as the sexual developmental form in cellular slime molds. ZYG1 is known to be involved in zygote formation by cell fusion during macrocyst formation in Dictyostelium mucoroides, one of the species of cellular slime molds.
Aim and methods: To know the effects of ZYG1 on the asexual and sexual development in Dictyostelium discoideum, an another species of cellular slime molds, we observed the developmental process and forms of a transformant (GFP-ZYG1OE) derived from Dictyostelium discoideum, in which GFP-ZYG1 fusion protein is overproduced.
Results: GFP-ZYG1OE cells were developed without or with an opposite mating type, V12M2 cells. When GFP-ZYG1OE cells were developed without V12M2 cells, they formed macrocyst-like structures consisting of a central cell mass and a thick transparent macrocyst wall surrounding it. It was suggested that transparent zones in the macrocyst wall were formed by cell fusion. When GFP-ZYG1OE cells were developed with V12M2 cells, globular bodies which are likely the macrocysts surrounded by thin cellulosic walls were found besides macrocysts. They were formed directly from zygotic giant cells without the formation of cell aggregates. The formation of the globular body is not caused by ZYG1 overproduction, because GFPCONT cells, a transformant overproducing GFP protein as controls, also formed globular bodies.
Conclusion: By the use of GFP-ZYG1OE cells overproducing GFP-ZYG1 fusion protein, it is revealed that ZYG1 is closely involved in macrocyst wall formation. This is the new finding concerning the function of ZYG1. In addition, the formation of a globular body, which is likely the macrocyst surrounded by a thin cellulosic wall, is demonstrated as a novel process of sexual development.
Keywords: Dictyostelium, cellulose, cell fusion, macrocyst wall, ZYG1