Haga N
Department of Biotechnology, Ishinomaki Senshu University, Miyagi, Japan.
J Cell Sci. 1995 Dec;108 ( Pt 12):3671-6. doi: 10.1242/jcs.108.12.3671.
The expression of sexual activity in Paramecium caudatum is repressed for about 50 fissions after conjugation. The ability of the macronucleus to affect the expression of sexual activity according to the age of clonal development was investigated using the macronuclear fusion-reorganization method. When a mature macronucleus was transplanted into an immature cell and fused with a macronucleus in the immature cell, the clones derived from the recipient showed sexual immaturity. In a reverse experiment, an immature macronucleus was transplanted into a mature cell, and the clones also showed sexual immaturity. The ability of the macronucleus to transform mature cells to immature cells was clonal age-dependent. The characteristics of the immature-mature hybrid macronucleus indicate that the immature macronucleus is dominant over the mature macronucleus with respect to the ability to express sexual activity. On the other hand, in cells of the early immaturity period, the micronucleus, known as the germ nucleus, shows the ability to undergo meiosis and eventually to produce progeny under control of the mature macronucleus. The expression of sexual activity is thought to be governed by the clonal age of the macronucleus and not by the clonal age of the micronucleus or cytoplasm. The macronucleus seems to determine the ability to express sexual activity by counting post-conjugation divisions and keeping track of the age of the clone.
尾草履虫接合后的性活动表达在约50次分裂中受到抑制。利用大核融合重组方法，研究了大核根据克隆发育年龄影响性活动表达的能力。当一个成熟大核移植到一个未成熟细胞中并与该未成熟细胞中的大核融合时，受体产生的克隆显示出性不成熟。在一个反向实验中，将一个未成熟大核移植到一个成熟细胞中，克隆也显示出性不成熟。大核将成熟细胞转化为未成熟细胞的能力取决于克隆年龄。未成熟 - 成熟杂种大核的特征表明，在表达性活动的能力方面，未成熟大核相对于成熟大核占主导地位。另一方面，在早期未成熟期的细胞中，被称为生殖核的小核在成熟大核的控制下表现出进行减数分裂并最终产生后代的能力。性活动的表达被认为是由大核的克隆年龄决定的，而不是由小核或细胞质的克隆年龄决定的。大核似乎通过计算接合后分裂次数并跟踪克隆年龄来决定表达性活动的能力。
