Rapid spatiotemporal patterning of cytosolic Ca2+ underlies flagellar excision in Chlamydomonas reinhardtii.
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+](cyt)) 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+](cyt), which was absent in the acid deflagellation-deficient adf1 mutant. Deflagellation could also be induced by elevated external Ca2+ ([Ca2+](ext)), which promoted very rapid spiking of [Ca2+](cyt) 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+](cyt) in the apical region of the cell, either in the form of a whole cell or an apically localised increase, indicating that [Ca2+](cyt) elevations in the apical region play an underlying role in deflagellation. Our data indicate that elevated [Ca2+](ext) acts to disrupt Ca2+ homeostasis which induces deflagellation by both Adf1-dependent and Adf1-independent mechanisms. Elevated [Ca2+](ext) also results in further [Ca2+](cyt) 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.
Wheeler
Glen L
GL
Plymouth Marine Laboratory, Prospect Place, Plymouth PL1 3DH, UK. glw@pml.ac.uk
Joint
Ian
I
Brownlee
Colin
C
D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000502:physiology; D016825:Chlamydomonas reinhardtii / Q000166:cytology / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism*; D005407:Flagella / Q000378:metabolism*; D018613:Microscopy, Confocal; D015398:Signal Transduction / Q000502:physiology
D002118:Calcium