A mutant of Chlamydomonas reinhardtii that lacks the flagellar outer dynein arm but can swim.
A mutant of Chlamydomonas reinhardtii that lacks the flagellar outer dynein arm but can swim.
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DOI：
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发表时间：
1985-03
影响因子：
4
通讯作者：
R. Kamiya;M. Okamoto
中科院分区：
文献类型：
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作者：
R. Kamiya;M. Okamoto
分离出一种新的衣原体突变体，它缺乏外动力蛋白臂，但可以游泳。十二烷基硫酸钠/聚丙烯酰胺凝胶电泳显示，四个动力蛋白的10个高分子量带中存在于野生型轴丝缺失或减少突变体轴丝。该突变体的游动速度约为35微米/秒，鞭毛振动频率约为25赫兹，两者均为野生型的1/2.5至1/3。突变体鞭毛跳动的不对称，纤毛型的模式，类似的向前游泳模式的鞭毛跳动的野生型。然而，与野生型鞭毛不同的是，突变体鞭毛从来没有以对称的波形跳动：当细胞受到强光刺激时，突变体暂时停止跳动其鞭毛，而野生型细胞暂时向后游动，两个鞭毛以对称的波形跳动。野生型和突变型细胞都可以通过Nonidet P40脱膜，并且在几乎不存在Ca 2+的情况下通过添加Mg-ATP重新激活它们的游泳。拍频对ATP浓度的双倒数图显示两种菌株的线性关系，产生最大频率为44 Hz（野生型）和23 Hz（突变型）。只有当Ca ~（2+）浓度低于10 ~（-6）M时，突变体轴丝才能被激活：在pCa ~（2+）浓度为4时，野生型轴丝以对称的波形搏动，而突变体轴丝则无运动。这些发现表明，外部动力蛋白臂是不对称波形（向前游泳模式）的鞭毛跳动，但不是对称波形（向后游泳模式）的跳动，从而表明外部动力蛋白臂在鞭毛波形的开关的重要性。
A new type of Chlamydomonas mutant, which lacks the outer dynein arm but can swim, was isolated. Sodium dodecyl sulphate/polyacrylamide gel electrophoresis showed that four of the ten high-molecular-weight bands of dynein present in the wild-type axoneme are missing or diminished in the mutant axoneme. The mutant has a swimming rate of about 35 micrometers/s and a flagellar beat frequency of about 25 Hz, both of which are about 1/2.5 to 1/3 of those of the wild type. The mutant flagella beat with an asymmetric, cilia-type pattern, similar to the forward-swimming mode of the flagellar beating pattern of the wild type. However, unlike wild-type flagella, the mutant flagella never beat with a symmetrical waveform: when the cells were stimulated by intense light, the mutant transiently stopped beating its flagella, whereas the wild-type cell transiently swam backwards with the two flagella beating with a symmetrical waveform. Both wild-type and mutant cells could be demembranated by Nonidet P40 and their swimming reactivated by addition of Mg-ATP in the virtual absence of Ca2+. Double reciprocal plots of the beat frequency against ATP concentrations showed a linear relationship for both strains, yielding maximal frequencies of 44 Hz (wild-type) and 23 Hz (mutant). The mutant axonemes can be reactivated only when the Ca2+ concentration is lower than 10(-6) M: at pCa4, the wild-type axonemes beat with a symmetrical waveform, but the mutant axonemes showed no movement. These findings indicate that the outer dynein arm is dispensable for flagellar beating of the asymmetric waveform (forward-swimming mode), but not for beating of the symmetrical waveform (backward-swimming mode), and thus suggest the importance of the outer dynein arm in the switching of flagellar waveforms.