Nuclear fusion in multinucleated giant cells during the sexual development of Dictyostelium discoideum

Ethylene as a potent inducer of sexual development

“…Fusion of two gametes has been photographed by a time-lapse video recorder in D. discoideum (O'Day et al 1987b). The appearance of nuclei containing a twofold DNA content has been also noticed in D. discoideum (Okada et al 1986). Taken together these results indicate that the giant cell is a true zygote produced by cell fusion and the subsequent nuclear fusion, in both kinds of mating behavior, homothallic and heterothallic.…”

“…There is a lot of evidence concerning the sexuality of macrocysts (Okada et al 1986;O'Day et al 1987a;Amagai 1989). Although the period of meiosis still remains to be specified, the appearance of synaptonemal complex, which is formed at the stage of late leptotene during meiosis is reported during macrocyst formation in some strains of cellular slime molds, such as Polysphondylium violaceum (Erdos et al 1972) and D. discoideum (Okada et al 1986). Furthermore, from various crossbreeding experiments, the occurrence of recombinants during macrocyst formation has been realized in Dm-7, its mutant (MacInnes & Francis 1974), D. giganteum (Erdos et al 1975), P. pallidum and D. discoideum (Francis 1975;Wallace & Raper 1979).…”

A Novel Function of Ethylene

“…The moment when two gametes fused has been photographed by a time lapse video recorder 21. The appearance of nuclei containing a two-fold DNA content has been also noticed 13. These results show that the giant cell is a true zygote produced by cell fusion and subsequent nuclear fusion, beyond the difference of mating types, homothallically or heterothallically.…”

“…Dm7, one of the strains of Dictyostelium mucoroides (Dm) has not a mating type and mates by itself homothallically. Since Raper12 described the process and sexuality of macrocyst formation, a lot of evidence concerning the sexuality of macrocysts has been accumulated 13–15. The sexual process is recognized by the appearance of a zygote which is formed by the cell fusion and subsequent nuclear fusion.…”

“…If cellular events such as cell fusion, nuclear fusion and meiosis are observed in the process of macrocyst formation, it is certainly recognized as the sexual process in cellular slime molds. Although the period of meiosis still remains to be specified, the synaptonemal complex which is formed at the late leptotene stage during meiosis appears during macrocyst formation in some strains of cellular slime molds, such as Polysphondylium violaceum (Pv)16 and Dd 13. Furthermore, from various hybridization breedings, the occurrence of recombinants during macrocyst formation has been realized in Dm7, its mutant,17 the heterothallic strains of D. giganteum (Dg),18 P. pallidum (Pp) and Dd 19,20.…”