SWEETs, transporters for intracellular and intercellular sugar translocation.Three families of transporters have been identified as key players in intercellular transport of sugars: MSTs (monosaccharide transporters), SUTs (sucrose transporters) and SWEETs (hexose and sucrose transporters).  MSTs and SUTs fall into the major facilitator superfamily; SWEETs constitute a structurally different class of transporters with only seven transmembrane spanning domains.  The predicted topology of SWEETs is supported by crystal structures of bacterial homologs (SemiSWEETs).  In rice and cassava, and possibly other systems, sucrose transporting SWEETs play central roles in pathogen resistance. 
SWEETs
SWEETs, transporters for intracellular and intercellular sugar translocation.Three families of transporters have been identified as key players in intercellular transport of sugars: MSTs (monosaccharide transporters), SUTs (sucrose transporters) and SWEETs (hexose and sucrose transporters).  MSTs and SUTs fall into the major facilitator superfamily; SWEETs constitute a structurally different class of transporters with only seven transmembrane spanning domains. 
MSTs
SWEETs, transporters for intracellular and intercellular sugar translocation.Three families of transporters have been identified as key players in intercellular transport of sugars: MSTs (monosaccharide transporters), SUTs (sucrose transporters) and SWEETs (hexose and sucrose transporters).  MSTs and SUTs fall into the major facilitator superfamily; SWEETs constitute a structurally different class of transporters with only seven transmembrane spanning domains.  In Arabidopsis, AtSWEET8 and 13 feed the pollen; SWEET11 and 12 provide sucrose to the SUTs for phloem loading; AtSWEET11, 12 and 15 have distinct roles in seed filling; AtSWEET16 and 17 are vacuolar hexose transporters; and SWEET9 is essential for nectar secretion. 
SUTs
The predicted topology of SWEETs is supported by crystal structures of bacterial homologs (SemiSWEETs). 
SemiSWEETs