Kamiya R, Witman G B
J Cell Biol. 1984 Jan;98(1):97-107. doi: 10.1083/jcb.98.1.97.
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.
当用去污剂提取衣藻的去膜细胞模型并将其重悬于钙离子浓度低于10⁻⁸ M的再激活溶液中时，许多模型最初以类似于完整细胞的螺旋路径游动；其他模型则贴着载玻片或盖玻片表面做圆周运动。再激活后随着时间的增加，以螺旋方式游动的模型减少，做圆周运动的模型增多。这种从螺旋游动到圆周游动的转变是其中一根轴丝逐渐失活的结果；在极端情况下，一根轴丝完全失活，而另一根则以正常波形摆动。在这些低钙离子浓度下，70% - 100%的模型中失活的轴丝是反轴丝（离眼点最远的那根）。在10⁻⁷或10⁻⁶ M钙离子浓度下，细胞模型也因一根轴丝失活而从螺旋游动转变为圆周游动；然而，在这些条件下通常是顺轴丝失活。在10⁻⁸ M钙离子浓度下，大多数细胞继续螺旋游动，这表明两根轴丝都保持相对活跃。分别将细胞模型切换到更高或更低的钙离子浓度可逆转反轴丝或顺轴丝逐渐的、依赖钙离子的失活。在含有0.5 mM乙二醇双四乙酸且未添加钙离子的培养基中游泳的完整细胞中，反鞭毛也发生了类似的可逆性、选择性失活。结果表明衣藻的两根轴丝存在功能差异。轴丝对亚微摩尔浓度钙离子的不同反应可能构成趋光转向的基础。
