Extended Data Figure 4: Sucrose, glucose and fructose transport activity of SWEETs in HEK293T cells and yeast cells.

a, b, Detection of glucose and sucrose uptake activity in HEK293T cells using the FRET glucose sensor FLII¹²Pglu700µδ6 and FRET sucrose sensor FLIPsuc90µδ3A. a, Glucose transport activity as detected for by co-expression with the cytosolic FRET glucose sensor FLII¹²Pglu700µδ6 in HEK293T cells. Individual cells were analysed by quantitative ratio imaging of enhanced cyan fluorescent protein (eCFP) and Citrine emission (acquisition interval, 5 s). HEK293T cells were perfused with culture medium, followed by square pulses of increasing glucose concentrations. Grey circle indicates cells expressing sensor alone; green triangle, red diamond and blue square indicate cells co-expressing sensor and AtSWEET9, BrSWEET9 or PtSWEET10, respectively, and orange circle indicates the positive control AtSWEET1; accumulation of glucose is indicated by a positive FRET ratio change (mean + s.e.m.; n > 10). Experiments were repeated with comparable results at least four times. b, Sucrose transport activity as detected for by co-expression with the cytosolic FRET sucrose sensor FLIPsuc90µδ3A in HEK293T cells. Individual cells were analysed by quantitative ratio imaging of eCFP and Aphrodite emission (acquisition interval, 10 s). HEK293T cells were perfused with culture medium, followed by square pulses of increasing sucrose concentrations. Grey circle indicates cells expressing sensor alone; green triangle, red diamond and blue square indicate cells co-expressing sensor, AtSWEET9 and BrSWEET9, respectively, circle indicates the positive control AtSWEET12 or PtSWEET10; accumulation of sucrose is indicated by a negative FRET ratio change (mean + s.e.m.; n > 10). Experiments were repeated with comparable results at least four times. c, Complementation of yeast EBY4000 (ref. 45) lacking 18 hexose transporter genes with AtSWEET1, NaSWEET9, AtSWEET9, AtSWEET11 or yeast HXT5 (positive control) transporters and empty vector (negative control). Left panel showed the medium containing glucose and right panel showed the medium containing fructose. AtSWEET1 showed glucose/fructose transport activity in yeast cells but NaSWEET9, AtSWEET9 and AtSWEET11 did not.