Submicromolar levels of calcium control the balance of beating between the two flagella in demembranated models of Chlamydomonas.
Submicromolar levels of calcium control the balance of beating between the two flagella in demembranated models of Chlamydomonas.
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DOI：
10.1083/jcb.98.1.97
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发表时间：
1984-01
期刊：
影响因子：
--
通讯作者：
Witman GB
中科院分区：
文献类型：
--
作者：
Kamiya R;Witman GB
当用去污剂提取、去膜的衣原体细胞模型重新悬浮在含有低于10（-8）M Ca++的再活化溶液中时，许多模型最初以类似于完整细胞的螺旋路径游动;其他模型则在载玻片或盖玻片表面上绕圈游动。随着再激活后时间的增加，较少的模型游泳螺旋和更多的游泳圈。这种从螺旋形到圆形游泳的转变是其中一个轴丝逐渐失活的结果;在极端情况下，一个轴丝完全不活动，而另一个轴丝以正常波形跳动。在这些低Ca++浓度下，在70-100%的模型中，失活的轴丝是跨轴丝（离眼点最远的轴丝）。在10（-7）或10（-6）M Ca++时，细胞模型也由于其中一个轴丝失活而从螺旋形游泳到环形游泳;然而，在这些条件下，顺式轴丝通常是失活的轴丝。在10（-8）M Ca++时，大多数细胞继续螺旋游动，表明两个轴丝保持相对活跃。通过将细胞模型分别切换到更高或更低的Ca++浓度，可以逆转反式或顺式轴丝的进行性Ca++依赖性失活。一个类似的可逆的，选择性失活的trans-flagellum发生在完整的细胞游泳在培养基中含有0.5 mM EGTA和没有添加Ca++。结果表明，披衣细胞的两个轴丝在功能上存在差异。轴丝对亚微摩尔浓度的Ca++的差异反应可能形成趋光转向的基础。
When detergent-extracted, demembranated cell models of Chlamydomonas were resuspended in reactivation solutions containing less than 10(-8) M Ca++, many models initially swam in helical paths similar to those of intact cells; others swam in circles against the surface of the slide or coverslip. With increasing time after reactivation, fewer models swam in helices and more swam in circles. This transition from helical to circular swimming was the result of a progressive inactivation of one of the axonemes; in the extreme case, one axoneme was completely inactive whereas the other beat with a normal waveform. At these low Ca++ concentrations, the inactivated axoneme was the trans-axoneme (the one farthest from the eyespot) in 70-100% of the models. At 10(-7) or 10(-6) M Ca++, cell models also proceeded from helical to circular swimming as a result of inactivation of one of the axonemes; however, under these conditions the cis-axoneme was usually the one that was inactivated. At 10(-8) M Ca++, most cells continued helical swimming, indicating that both axonemes were remaining relatively active. The progressive, Ca++-dependent inactivation of the trans- or cis-axoneme was reversed by switching the cell models to higher or lower Ca++ concentrations, respectively. A similar reversible, selective inactivation of the trans-flagellum occurred in intact cells swimming in medium containing 0.5 mM EGTA and no added Ca++. The results show that there are functional differences between the two axonemes of Chlamydomonas. The differential responses of the axonemes to submicromolar concentrations of Ca++ may form the basis for phototactic turning.