Molecular and cytological studies on the cell cycle regulation of marine multinucleate green algae.

与动物和高等植物中的纺锤体分裂不同，小灰木的核分裂过程中核膜不碎裂，是一种独特的核分裂过程。本研究利用抗β微管蛋白、抗中心蛋白和抗γ微管蛋白抗体，在免疫荧光显微镜下观察了小B.forbesii的有丝分裂过程。在间期，微管（MT）辐射周围的核。间期核周围有1 ~ 2对中心粒。有丝分裂时，核周MT消失，取而代之的是从中心粒放射出的MT。这些MT病灶分离并迁移到两极。同时，微管蛋白分子从分裂前期开始进入细胞核，形成从极到染色体、从极到极的纺锤体MT，最后形成带间纺锤体纤维。在整个细胞周期中，中心蛋白分子始终位于中心粒周围。相反，在间期中心粒周围未检测到γ-微管蛋白。在有丝分裂前期早期至后期早期，γ-微管蛋白特征性地分布于中心粒周围，而在后期和末期，在中心粒周围则观察不到γ-微管蛋白。此外，γ-微管蛋白没有本地化的带间梭形纤维。这意味着带间梭形纤维的两端都是MT的+端，而不是中心体。

Nuclear division in Boergesenia forbesii is very unique in the respect that the nuclear membrane is not fragmented throughout mitosis different from open-spindles in animals and higher plants. In this study, we observed the mitosis in B.forbesii under immunofluorescence microscopy using anti-beta tubulin, anti-centrin and anti-gamma tubulin antibodies. In interphase, microtubules (MTs) radiated around nuclei. One or two pairs of centrioles existed aroud the interphase nucleus. Toward mitosis, perinuclear MTs disappeared and, instead of them, MTs radiated from centrioles. These MT foci separated and migrated to both poles. Simultaneously, tublin molecules started to enter into the nucleus from prophase, and these tubulin molecules formed spindle MTs from poles to chromosomes and from pole to pole, and finally interzonal spindle fibers. Centrin molecules always localized around centrioles through the cell cycle of B.forbesii. On the contrary, gamma-tubulin could not detected around centrioles in interphase. Gamma-tubulin characteristically localized around centrioles from early prophase to early anaphase in mitosis, and they could not be observed around centrioles in late anaphase and telophase. Moreover, gamma-tubulin did not localize in the interzonal spindle fibers. This means that both ends of the interzonal spindle fibers are +end of MTs, not like centrosome.