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First published online January 8, 2007
Journal of Experimental Biology 210, 357-365 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.02642
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Genetic dissection of attractant-induced conductances in Paramecium

Wade E. Bell1, Robin R. Preston2, Junji Yano3 and Judith L. Van Houten3,*

1 Department of Biology, 203 Science Building, Virginia Military Institute, Lexington, VA 24450, USA
2 Department of Pharmacology and Physiology, Drexel University, Philadelphia, PA 19102, USA
3 Department of Biology, University of Vermont, Burlington, VT 05405, USA

* Author for correspondence (e-mail: Judith.Vanhouten{at}uvm.edu)

Accepted 8 November 2006

Paramecium tetraurelia is attracted to acetate and biotin by swimming smoothly and fast up gradients of these attractants, and turning immediately and slowing down when leaving these stimuli. We use a group of mutants, each with a different defect in an identified ion conductance, to show that these two stimuli open different ion channels, and the behaviors that occur upon application of stimulus (on-response) and removal of stimulus (off-response) have different roles in attraction to these two stimuli. The most important parameters for successful attraction to acetate are the on-response behaviors of fast swimming with few turns, and the mutants' behavior suggests that IK(Ca,h) is the conductance involved that initiates this behavior. IK(Ca,h or d) appears to be important to the on-response in biotin; the results with mutants suggest that the biotin off-response depolarization is initiated by an ICa, which can be large enough or close enough to channels to open IK(Ca,d), INa(Ca) and IMg(Ca).

Key words: Paramecium, mutant, conductance, chemoattraction, channel, biotin, acetate






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