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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 Houten^3,*

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

View larger version (14K): [in this window] [in a new window]   Fig. 1. Voltage-clamp recordings from cells in acetate or biotin. The cells were held at resting potential (-30 mV) using two-electrode voltage-clamp. (A) Solid bars indicate application of 1 mmol l-1 acetate. Lower two traces were recorded using K+-filled electrodes with 1 mmol l-1 K+ in the bath. K+ currents were suppressed in the middle and upper traces using CsCl and tetraethylammonium (TEA), leaving Ca2+ (1 mmol l-1) and Mg2+ (5 mmol l-1) as the predominant charge carriers. Arrows show the outward conductances upon addition of acetate and removal of acetate. (B) Solid bars indicate application of variable concentrations of biotin at variable pH. K+ currents were suppressed in the middle and upper traces using CsCl and TEA leaving Ca2+ (1 mmol l-1) and Mg2+ (5 mmol l-1) as the predominant charge carriers. Arrows show the inward conductances upon removal of biotin.

View larger version (24K): [in this window] [in a new window]   Fig. 2. Behavior of cells entering and leaving acetate. Cells were analyzed using Motion Analysis as they entered 5 mmol l-1 acetate in buffer from a control buffer or vice versa. Cells were monitored for turns (% change in direction, PDC) and speed. (A) Cell turning upon entering acetate (On PDC); (B) cell turning upon leaving acetate (Off PDC); (C) speed in mm s-1 upon entering acetate (On speed). (A) Wild-type, Cam 11 and XntA On PDCs were significantly different from Controls. (B) Wild type and Cam 11 Off PDCs were significantly different from Controls. (C) Wild-type and Cam 11 speeds were significantly different from control (Mann-Whitney U-test, P<0.05). The wild-type and XntA cells were analyzed in Na-acetate; Cam 1-1 and Cam 11 were analyzed in K-acetate. (Values are means ± 1 s.e.m. of 45 or more measurements.)

View larger version (17K): [in this window] [in a new window]   Fig. 3. Cell behavior upon entering or leaving acetate. The data from Fig. 2 were transformed into differences between the control value and experimental value for on- and off-response PDCs (A) and on-response speed in mm s-1 (B). (C) The T-maze values for wild type and mutants in A and B. (Values >0.5 indicate attraction, <0.5 indicate repulsion.) Arrow indicates significant difference with wild type at P<0.01, Mann-Whitney U-test.

View larger version (22K): [in this window] [in a new window]   Fig. 4. Behavior of cells entering and leaving biotin solutions. Cells were analyzed using Motion Analysis as they entered 1 mmol l-1 biotin in buffer from a control buffer or vice versa. Cells were monitored for turns (% change in direction, PDC) and speed. (A) Cell turning upon entering biotin (On PDC); (B) the T-maze values for the wild type and mutants in biotin for comparison with A because the T-maze values correlate well with On-PDC responses; (C) Cell turning upon leaving biotin (Off PDC). (A) Cam 1-1 and wild type in Na-biotin On PDCs were significantly different from Controls (P<0.05). (B) All Values are means ± 1 s.e.m. of 45 or more measurements. Mann-Whitney U-test was used for statistical analysis of T-maze data; all values except for Cam 11 were different from wild type in Na+ and Mg2+ at P<0.05 level. (C) Wild type in Mg-biotin and Cam1-1 Off PDCs were significantly different from Controls. The wild type cells were analyzed in K-biotin pH 6.7, Na-biotin pH 7, Mg-biotin pH 7; Cam 1-1 in Na-biotin pH 7; Cam 11 K-biotin pH 6.7; XntA in Na-biotin pH 7 and Mg-biotin pH 7.

View larger version (9K): [in this window] [in a new window]   Fig. 5. Cell behavior upon entering or leaving biotin solutions. The data from Fig. 4 were transformed into differences between the control value and experimental value for on- and off-response PDCs.