Photolysis of caged calcium in cilia induces ciliary reversal inParamecium caudatum

Abstract

SUMMARYIntracellular Ca2+ 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 Ca2+ levels. Despite this, the Ca2+-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 Ca2+ level([Ca2+]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 Ca2+-sensitive region for ciliary reversal is distributed all over the cilium, above the basal body.