| Research Abstract |
Through this study, we observed the behavior of centrioles in zygotes in the fertilization of the brown algae ; Scytosiphon lomentaria (isogamy), Cut leria cylindrica (anisogamy) and Fucus distichus (oogamy). In all cases, centrioles derived from female gametes had disappeared in zygotes after plasmogamy, and we concluded that the paternal inheritance of centrioles is a common feature in the brown algae, although various patterns of sexual reproduction exists. could be universal in the brown algae.
Next, the influence of the centrioles, derived from the sperm flagellar basal bodies, and the centrosomal material (MTOCs) on spindle formation in the brown alga Fucus distichus (oogamous) was studied. A multipolar spindle was formed in polyspermic zygote. The number of mitotic poles in polyspermic zygotes was double the number of sperminvolved in the fertilization. A pair of centrioles which can be detected by anti-centrin antibody was located at these poles. When anucleate egg fragments were fertilized, two anti-centrin staining spots could be detected near the sperm nucleus. Microtubules radiated from nearby them, but the mitotic spindle was never produced. When a single sperm fertilized multinucleate eggs, abnormal spindles were also observed. in addition to two mitotic poles containing anti-centrin staining spots, extra mitotic poles without anti-centrin staining spots were also formed, and as a result, multipolar spindles were formed. When karyogamy was blocked with colchicine, a monoastral spindle could be frequently observed, and in rare cases, a barrel-shaped spindle without centrioles was formed in the egg nucleus. From these results, it became clear that paternal centrioles derived from the sperm have a crucial role in spindle formation in the brown algae, like they do during animal fertilization. But paternal centrioles were not enough for the functional centrosome during spindle formation.
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