Delayed degradation of parental macronuclear DNA in programmed nuclear death of Paramecium caudatum
Delayed degradation of parental macronuclear DNA in programmed nuclear death of Paramecium caudatum
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DOI：
10.1002/gene.20060
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发表时间：
2004-09
期刊：
影响因子：
1.5
通讯作者：
N. Kimura;K. Mikami;H. Endoh
中科院分区：
文献类型：
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作者：
N. Kimura;K. Mikami;H. Endoh
在纤毛原生动物尾草履虫中，亲本大核在接合过程中被碎裂成约40-50个片段，不会立即退化，而是持续到接合后的第八个细胞周期。在这里，我们证明了亲本大核变性的开始大约发生在第五个细胞周期。亲本大核片段的大小在第一个细胞周期和第四个细胞周期之间持续增大，但之后逐渐减小。相比之下，一个新的大核生长并在第四个细胞周期达到最大尺寸，表明新的大核在那个阶段成熟。Southern杂交分析表明，亲本大核DNA在第5个细胞周期左右降解。吖啶橙染色支持降解，表明大核碎片变性。在降解之前，曾经附着在新的大核上的碎片随后被从它身上释放出来。这些观察使我们得出结论，一旦新的大核在第四个细胞周期完全形成，父母的大核片段注定会退化，可能是通过新的大核的方向。考虑到亲本大核在接合后的早期细胞周期中的持续时间较长，大核碎片可能在不完善的新大核成熟过程中起作用。讨论了两种可能的功能：基因剂量补偿和倍性水平的调节。创世纪40：15-21,2004。©2004 Wiley-Liss Inc.
In the ciliated protozoan Paramecium caudatum, a parental macronucleus that is fragmented into some 40–50 pieces during conjugation does not degenerate immediately, but persists until the eighth cell cycle after conjugation. Here we demonstrate that the initiation of the parental macronuclear degeneration occurs at about the fifth cell cycle. The size of parental macronuclear fragments continued to increase between the first and fourth cell cycle, but gradually decreased thereafter. By contrast, a new macronucleus grew and reached a maximum size by the fourth cell cycle, suggesting that the new macronucleus matured by that stage. Southern blot analysis revealed that parental macronuclear DNA was degraded at about the fifth cell cycle. The degradation was supported by acridine orange staining, indicating degeneration of the macronuclear fragments. Prior to the degradation, the fragments once attached to the new macronucleus were subsequently liberated from it. These observations lead us to conclude that once a new macronucleus has been fully formed by the fourth cell cycle, the parental macronuclear fragments are destined to degenerate, probably through direction by new macronucleus. Considering the long persistence of the parental macronucleus during the early cell cycles after conjugation, the macronuclear fragments might function in the maturation of the imperfect new macronucleus. Two possible functions, a gene dosage compensation and adjustment of ploidy level, are discussed. genesis 40:15–21, 2004. © 2004 Wiley‐Liss, Inc.