洋葱类胀泡结构和α-鹅膏蕈碱对该结构的影响

THE PUFF-LIKE STRUCTURE IN ALLIUM CEPA AND THE EFFECT OF α-AMANITIN TREATMENT UPON THE STRUCTURE

研究了洋葱(Allium cepa L.)根端分生组织细胞核中的类胀泡结构(PLS)和 mRNA合成抑制剂α-鹅膏蕈碱(α-A)对该结构的影响。发现组成 PLS 的直径30—50nm 的纤维具有两种存在状态:一种比较致密,另一种则较疏松。在疏松纤维构成的 PLS 中能够观察到由轴纤维和侧向纤维组成的毛刷样构造。Bernhard 染色结果表明,PLS 中既有 RNP 含量较高的纤维,也有 DNP 含量较高的区域。在经α—A处理的样品中,仅能观察到由致密纤维组成的 PLS,而疏松纤维组成的 PLS 遭到破坏,其中看不到毛刷样构造。讨论了α—A对 PLS的影响,并推测 PLS 可能是植物根端分生组织细胞核中非核仁基因转录合成 mRNA 的一种结构。

The puff-like structure (PLS) is a loose, flbrillar, spherical structure which has been found in the nucleus of some higher' plants and often referred to intranuclear bodies, centromeres, micro- puffs and puff-like fibrillar structures. Opinions on the nature of the PLS are still diverged. In order to gain further information upon the nature of the structure, ultrastructural and cytoche- mical features of the PLS in the nucleus of root tip meristematic cells of Allium cepa L. and the effect of a-amanitin(a-A, a specific inhibitor of RNA polymerase II which is responsible for the tianscription of genes coding for mRNA) on it were studied. Two types of PLSs were found in the conventionally-stained samples: one was composed of compact fibres while the other consisted of loose, decondensed fibres. In the PLS of the latter type, a brush-like structure comprising both an axial fibre and lateral fibres was observed, suggesting that transcription was taking place in the PLS. When stained by Bernhard's method, the PLS was shown to contain both RNP and DNP. After.the treatment with a-A, the PLS composed of compact fibres was still seen bat he one consisting of loose fibres was destroyed ultrastructurally and the brush-like structures di- sappeared. Based on these observations, it is suggested that the PLS would be a morphological manifestation of transcription of the non-nucleolar gene coding for mRNA.