Immunological analysis of chromatin differentiation in higher plant cells

本研究利用特异性抗血清，在麝香百合雄配子核（生殖核和精子核）的碱性蛋白质中，检测到3种在小孢子发生和花粉发育过程中具有特异时空分布的组蛋白变异体。一种是减数分裂组蛋白（mHl），其已被报道为组蛋白Hl样蛋白。它出现在小孢子母细胞减数分裂之前，并且在小孢子发生和大孢子发生期间优先定位于着丝粒/动粒上。利用该抗血清，我们能够观察到前期Ⅰ同源染色体的着丝粒融合和分离，后期的姐妹着丝粒不分离，后期Ⅱ分离以及着丝粒与纺锤体微管的连接。第二组是gHl，其也是组蛋白Hl的变体。它不是配子发生特异性蛋白，但在雄配子核中大量积累。在单子叶、双子叶等高等植物细胞的核仁中，以及百合体细胞和早期生殖细胞的核仁中，都存在类似的蛋白质。最后是雄性配子特异性的核心组蛋白变体，它们被命名为gH 2A、gH 2B和gH 3。它们出现在小孢子有丝分裂后的双细胞花粉发育过程中，并特异性地定位于生殖核和精核中。但是，它们靶向于体细胞中的核仁。从这些观察，它被假定，这些组蛋白变体是密切相关的特定的染色质组织和染色质组织的雄配子核是类似的核仁。

In this study, using specific antisera, we have detected three kinds of histone variant, that shows specific temporal and spatial distribution during microsporogenesis and pollen development, among basic proteins included in male gametic (generative and sperm) nuclei of Lilium longiflorum. One is a meiotic histone (mHl), which had been reported to be a histone Hl-like protein. It appears preceding meiotic division in microsporocytes and is preferentially localized on the centromeres/kinetochores during microsporogenesis and megasporogenesis. Using this antiserum, we were able to visualize the fusion and disjunction of centromeres of homologous chromosomes in prophase I, nonseparation of the sister centromeres at anaphase,, separation of them at anaphase II and the attachment of the centromeres to spindle microtubules. Second group is a gHl, which is also a variant of histone Hl. It is not a gametogenesis-specific protein, but abundantly accumulates in the male gametic nuclei. The analogous proteins are present in nucleoli of higher plant cells including monocotyledon and dicotyledon as well as in nucleoli of somatic and early reproductive cells of this lily. Last are male gamete-specific, core histone variants, that were designated gH2A, gH2B and gH3. They appear during the development of bicellular pollen after microspore mitosis and are specifically localized in the generative and sperm nuclei. But, they were targeted to the nucleoli in somatic cells. From these observations, it is assumed that these histone variants are closely related to specific chromatin organization and the chromatin organization of the male gametic nuclei is similar to that of nucleolus.