Wheeler Glen L, Joint Ian, Brownlee Colin
Plymouth Marine Laboratory, Prospect Place, Plymouth PL1 3DH, UK.
Plant J. 2008 Feb;53(3):401-13. doi: 10.1111/j.1365-313X.2007.03349.x. Epub 2007 Dec 12.
Ca(2+)-dependent signalling processes are implicated in many aspects of flagella function in the green alga, Chlamydomonas. In this study, we examine the spatiotemporal dynamics of cytosolic Ca2+ (Ca2+) in single Chlamydomonas cells during the process of flagellar excision, using biolistically loaded calcium-responsive dyes. Acid-induced deflagellation occurred in parallel with a single transient elevation in whole-cell Ca2+, which was absent in the acid deflagellation-deficient adf1 mutant. Deflagellation could also be induced by elevated external Ca2+ (Ca2+), which promoted very rapid spiking of Ca2+ across the whole cell and in the flagella. We also detected very rapid apically localised Ca2+ signalling events with an approximate duration of 500 msec. Ninety-seven per cent of deflagellation events coincided with a rapid elevation in Ca2+ in the apical region of the cell, either in the form of a whole cell or an apically localised increase, indicating that Ca2+ elevations in the apical region play an underlying role in deflagellation. Our data indicate that elevated Ca2+ acts to disrupt Ca2+ homeostasis which induces deflagellation by both Adf1-dependent and Adf1-independent mechanisms. Elevated Ca2+ also results in further Ca2+ elevations after the main period of whole cell spiking which are very strongly associated with deflagellation, exhibit a high degree of apical localisation and are largely absent in the adf1 mutant. We propose that these later elevations may act as specific signals for deflagellation.
钙离子（Ca²⁺）依赖的信号传导过程与绿藻莱茵衣藻鞭毛功能的许多方面有关。在本研究中，我们使用生物弹道加载的钙响应染料，研究了单个莱茵衣藻细胞在鞭毛切除过程中胞质Ca²⁺（[Ca²⁺]（cyt））的时空动态。酸诱导的去鞭毛作用与全细胞[Ca²⁺]（cyt）的单次瞬时升高同时发生，而在酸诱导去鞭毛缺陷的adf1突变体中则不存在这种情况。外部Ca²⁺（[Ca²⁺]（ext））升高也可诱导去鞭毛作用，这促进了[Ca²⁺]（cyt）在整个细胞和鞭毛中的非常快速的尖峰变化。我们还检测到非常快速的顶端局部Ca²⁺信号事件，持续时间约为500毫秒。97%的去鞭毛事件与细胞顶端区域[Ca²⁺]（cyt）的快速升高同时发生，其形式为全细胞或顶端局部增加，表明顶端区域[Ca²⁺]（cyt）的升高在去鞭毛作用中起潜在作用。我们的数据表明，升高的[Ca²⁺]（ext）会破坏Ca²⁺稳态，通过Adf1依赖和Adf1独立机制诱导去鞭毛作用。升高的[Ca²⁺]（ext）还会在全细胞尖峰的主要时期之后导致[Ca²⁺]（cyt）进一步升高，这与去鞭毛作用密切相关，表现出高度的顶端局部化，并且在adf1突变体中基本不存在。我们提出，这些后期升高可能作为去鞭毛作用的特定信号。
