Fig. 5.

CO₂ conductance of AtPIP2;5 expressed in yeast. (A) Fluorescence intensity for yeast cells loaded with fluorescein diacetate measured at 0.125 ms intervals. Intracellular acidification in response to the entry of CO₂ causes a decrease in the fluorescence intensity of yeast cells. Average curves with 95% confidence intervals are presented. (B) CO₂-induced intracellular acidification rate of S. cerevisiae cells expressing AtPIP2;5, AtCA1, or both. Yeast cells were exposed in a ratio of 1:1 (v/v) to a CO₂-mixing buffer (25 mM HEPES, 75 mM NaHCO₃, pH 6). Kinetics of acidification were measured with an excitation wavelength of 460 nm and emission above 515 nm using a stopped-flow spectrophotometer. Bars represent the CO₂ permeability of yeast expressed as the exponential decay rate of fluorescence intensity. The kinetics of the decrease in fluorescence were obtained by fitting an exponential decay function to these curves in order to calculate the rate constants. Values are means ±SD of three replicates, and each replicate was comprised of six technical repeats. Different letters denote statistically different values at P<0.05.