Photolysis of caged calcium in cilia induces ciliary reversal inParamecium caudatum

Abstract

Intracellular Ca 2+ concentration controls both the pattern and frequency of ciliary and flagellar beating in eukaryotes. In Paramecium, it is widely accepted that the reversal of the direction of ciliary beating (ciliary reversal) is induced by an increase in intra-ciliary Ca 2+ levels. Despite this, the Ca 2+ -sensitive region of the cilium that initiates ciliary reversal has not been clearly identified.We injected caged calcium into living P. caudatum cells and applied ultraviolet (UV) light to portions of the injected cells to raise artificially the intracellular Ca 2+ level ([Ca 2+ ]i). UV application to the upper ciliary region above the basal body induced ciliary reversal in injected cells. Furthermore, UV application to the tips of cilia induced weak ciliary reversal. Larger areas of photolysis in the cilium gave rise to greater angles of ciliary reversal. These results strongly suggest that the Ca 2+ -sensitive region for ciliary reversal is distributed all over the cilium, above the basal body.Movies available on line

One-way calcium spill-over during signal transduction in Paramecium cells: from the cell cortex into cilia, but not in the reverse direction

“…They found that basal regions are more sensitive than more distal ones. More recently, Iwadate [37] found by laser activation of caged Ca 2+ that the distal part of cilia also contains the Ca 2+ -sensitive machinery relevant for ciliary beat reversal.…”

“…Difficulties in determining precise free Ca 2+ concentrations, [Ca 2+ ], within cilia and flagella have several reasons, not only the small size, but also unknown diffusion effects [30] after passing Ca 2+ -channels whose distribution along the cilium is unknown (see "Section 4"), as is that of a still increasing number of Ca 2+ -activated and Ca 2+ -binding proteins (CaBPs) [31][32][33][34][35], not to speak of practical problems with fluorochrome analyses in these slender and highly motile structures. Alternative methods, like intracellular application of Ca 2+ chelators of different k D or local photoactivation of caged Ca 2+ , as it is widely used in exocytosis research [36], proved useful merely on a rather coarse scale, at best to compare proximal and distal regions of cilia in Paramecium [37].…”

Ciliary metachronal wave propagation on the compliant surface of Paramecium cells

“…The direction of ciliary beat in Paramecium cells is then reversed by a rise in intraciliary Ca 2+ concentration [Naitoh and Eckert, ; Naitoh and Kaneko, ; Iwadate, ]. We applied UV light to a small patch of cilia on a Paramecium cell that had been previously injected with NP‐EGTA medium (white circle in Fig.…”

“…The injected volume of medium was approximately 8 pl, corresponding to about 3% of the whole cell volume. Ultraviolet (UV) irradiation of the local area was performed according to the methods described previously [Iwadate, ; Iwadate and Nakaoka, ] with slight modifications. An inverted microscope (TE300, Nikon, Tokyo, Japan) was used throughout the experiment.…”

Mitigation of copper toxicity by DNA oligomers in green paramecia

“…24 Therefore, most visible event with involvement of calcium signaling in Paramecium species is ciliary reversal which depends on the intracellular increase in Ca 2C concentration. 25 It has long been known that members of Paramecium species including P. bursaria exhibit galvanotaxis, a directed swimming of cells toward the electrode, induced in response to an applied voltage. 23,26 A pharmacological approach has revealed that T-type calcium channels are involved in galvanotactic movement of P. bursaria involving electrically forced ciliary reversal, as galvanotactic behavior was shown to be sensitive to a variety of Ca 2C -related inhibitors such as Ca 2C chelators, inhibitors of intracellular Ca 2C release (such as ruthenium red and neomycin), lanthanide ions (general calcium channel blockers), and inhibitors of T-type calcium channels (such as NNC 55-0396, 1-octanol and Ni 2C ), while inhibitors of Ltype calcium channels such as nimodipine, nifedipine, verapamil, diltiazem and Cd 2C all failed to block the galvanotactic movement of P. bursaria.…”