A novel class of transporter protein, referred to as SWEET, GLUE or Glü, is disclosed. These transporters provide a novel system for the transportation of sugars across membranes within a cell and between the inside and outside of a cell. Such transporters are useful for understanding and altering the sugar concentration within certain organs of an organism, and within certain organelles within the cell. These transporters are also useful in protecting plants from a pathogen attack.