Modification of the surface carbohydrate composition of tobacco protoplasts transformed with the human UDP-galactose transporter gene hUGT1

Tobacco BY-2 cells were transformed with the human UDP-galactose transporter 1 gene (hUGT1) under the control of a 35S promoter. Accumulation of mRNA and protein derived from hUGT1 was detected in the hUGT1- transformed BY-2 cells. To identify the cell surface carbohydrates, BY-2 protoplasts were treated with 21 kinds of biotinylated lectin, stained with fluorescein isothiocyanate (FITC)-conjugated streptavidin and observed by fluorescence microscopy. FITC-ConA and -RCA120 staining exhibited strong fluorescence on the surface of BY-2 protoplasts, whereas staining with other FITC-lectin conjugates showed faint or no fluorescence. Regarding FITC-ConA and -RCA120 staining, the fluorescence of hUGT-expressing BY-2 protoplasts was weaker than that of control cells. Decreased FITC fluorescence of hUGT-expressing BY-2 protoplasts was also detected by fluorescence-activated cell sorting (FACS) analysis, suggesting that the surface carbohydrate composition was modified.