Sugar Transport By Sweets: From Structures to Biosensors

The SWEETs are a family of sugar transporters conserved in prokaryotes, plants and animals. In plants, they play key roles in numerous physiological processes including phloem loading, pollen nutrition, nectar secretion and pathogen susceptibility. We have performed extensive functional characterization of this family based on the atomic structures of their bacterial homologues (the SemiSWEET) and the vacuolar glucose transporter OsSWEET2b from rice. We take advantage of these atomic structures and a high throughput cell sorting approach to create a set of SWEET biosensors composed of transporter-fluorescent protein fusions. We use our biosensors to quantify the kinetics of the SWEETs, and to gain further insight into the molecular mechanisms underlying selectivity and gating.