Esculin uptake by yeast expressing sucrose transporter cDNAs. Yeast (SEY6210) transformed with plant sucrose transporters StSUT1, AtSUC2, OsSUT1 or vector control (pDR196), indicated on the left, were incubated for one hour in 1 mM esculin in 25 mM sodium phosphate buffer (pH 4.0). The cells were washed and visualized at 1000× magnification using differential contrast (DIC, column 1) or fluorescence microscopy (column 2). For fluorescence microscopy the following filters were used: excitation filter 426-446 nm, 455 nm LP dichroic mirror, 460-500 nm emission filter. The DIC and fluorescence images were overlaid as shown in column 3.