Cell division cycle (cdc) mutants of Saccharomyces cerevisiae were used to determine the most effective stage for the directional control of cell budding using an electric stimulus. The selected mutants were cdc 35 and cdc 28, which could be reversibly arrested before spindle pole body satellite formation (SPBSF) and spindle pole body duplication (SPBD), respectively. The budding direction (theta) was defined so that the direction parallel to that of the electric field was 0 degree. Considering the symmetry of the experimental conditions, the range of theta was defined as 0-90 degrees. The electric stimulus applied in the present study was alternating pulses (pulse height, +/- 15 V; pulse width at half pulse height, 5 microseconds; frequency; 10 kHz). The peak height of the cross membrane potential was estimated as 472 mV, which was sufficient to induce considerable strain in the cell membrane. In the case of cdc 35, the 95% confidence interval (95% CI) of the budding direction was 7-25 degrees when subjected to electric stimulus, while the 95% CI of the budding direction without electric stimulus was 35-57 degrees. In the case of cdc 28, 95% CI values of the budding direction with and without electric stimulus were 1229 degrees and 23-56 degrees, respectively. These results demonstrate that the stage after SPBD is effective for the directional control of yeast cell budding using an electric stimulus. Simultaneously, an electric stimulus reduced the cell budding time of both the cdc mutants used. Therefore, the electric stimulus was also effective in promoting cell cycle progression under the present conditions.
