Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov str. 32, Moscow 119991, Russia.
Biol Res. 2013;46(1):69-74. doi: 10.4067/S0716-97602013000100010.
We have earlier shown that the typical Didinium nasutum nucleolus is a complex convoluted branched domain, comprising a dense fibrillar component located at the periphery of the nucleolus and a granular component located in the central part. Here our main interest was to study quantitatively the spatial distribution of nucleolar chromatin structures in these convoluted nucleoli. There are no "classical" fibrillar centers in D.nasutum nucleoli. The spatial distribution of nucleolar chromatin bodies, which play the role of nucleolar organizers in the macronucleus of D.nasutum, was studied using 3D reconstructions based on serial ultrathin sections. The relative number of nucleolar chromatin bodies was determined in macronuclei of recently fed, starved D.nasutum cells and in resting cysts. This parameter is shown to correlate with the activity of the nucleolus. However, the relative number of nucleolar chromatin bodies in different regions of the same convoluted nucleolus is approximately the same. This finding suggests equal activity in different parts of the nucleolar domain and indicates the existence of some molecular mechanism enabling it to synchronize this activity in D. nasutum nucleoli. Our data show that D. nasutum nucleoli display bipartite structure. All nucleolar chromatin bodies are shown to be located outside of nucleoli, at the periphery of the fibrillar component.
我们之前已经表明，典型的双滴虫类核仁是一个复杂的卷曲分支域，由位于核仁外围的密集纤维状成分和位于中央部分的颗粒状成分组成。在这里，我们主要感兴趣的是定量研究这些卷曲核仁中核仁染色质结构的空间分布。双滴虫类核仁中没有“经典”的纤维中心。使用基于连续超薄切片的 3D 重建，研究了在双滴虫类巨核中充当核仁组织者的核仁染色质体的空间分布。在最近喂食的、饥饿的双滴虫细胞的巨核和静止的胞囊中转录因子活性测定了核仁染色质体的相对数量。该参数与核仁的活性相关。然而，同一个卷曲核仁的不同区域的核仁染色质体的相对数量大致相同。这一发现表明核仁域的不同部分具有相同的活性，并表明存在某种分子机制使双滴虫类核仁能够同步这种活性。我们的数据表明，双滴虫类核仁显示出二分体结构。所有核仁染色质体都位于核仁外部，纤维状成分的外围。
