title: Gamete fusion and cytokinesis preceding zygote establishment in the sexual process of Dictyostelium discoideum.
abstract: Cells of Dictyostelium discoideum become sexually mature under submerged and dark conditions, and fuse with opposite mating-type cells to form zygote giant cells, which gather surrounding cells and finally develop into dormant structures called macrocysts. In the present study, we found that the multinuclear fused cells formed during this process frequently underwent cytokinesis driven by random local movements. The split cells were capable of re-fusion, and repeated cytokinesis. These radical behaviors continued until the extensive cell aggregation started around the giant cells. Thus, gamete fusion and initiation of zygote development do not coincide in the mating of D. discoideum. Analyses by confocal microscopy and flow cytometry indicated that the cessation of the random movement followed pronuclear fusion, and that microtubule organizing centers (MTOC), abundant in the fused cells at the beginning, gradually decreased and only one of them remained within the developed macrocyst. Some of the genes known to control cell movement, such as rasGEFB and rasS, increased shortly before the cessation of repeated fusion-cytokinesis and initiation of phagocytosis. These results suggest that the sequential molecular events are necessary in D. discoideum after gamete fusion to establish a new individuality of zygotes.
authors.affiliation: Graduate School of Life and Environmental sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba-shi 305-8572, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Ishida
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Hata
authors.forename: Hideko
authors.initials: H
authors.lastname: Urushihara
mesh_terms: D000818:Animals; D002459:Cell Fusion; D002465:Cell Movement / Q000502:physiology*; D048749:Cytokinesis / Q000502:physiology*; D004023:Dictyostelium / Q000166:cytology* / Q000378:metabolism / Q000502:physiology*; D005306:Fertilization / Q000502:physiology; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D049452:Green Fluorescent Proteins; D018613:Microscopy, Confocal; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013084:Sperm-Ovum Interactions / Q000502:physiology*; D013997:Time Factors; D014404:Tubulin / Q000378:metabolism
chemical_list: D014404:Tubulin; D049452:Green Fluorescent Proteins