Novel Vacuolar Sugar Transporters from Tomato

Abstract

ugar transporters play indispensable roles in sugar transport within and between cells and also in long distance carbon distribution. Sugar transporters of plants are classified in eight families and two homologues of SFP family (SlSFP1 and SlSFP2) were found in a tomato EST library generated by KAZUSA DNA Res. Inst. SlSFP1 and SlSFP2 encode proteins of 486 and 490 amino acids, respectively, and both have 12 putative trans-membrane domains and typical sugar transporter motifs. Real-time PCR analysis revealed that SlSFP1 expression is especially high in early and late stages of tomato fruit development, while SlSFP2 expression is almost constant during fruit development and in other organs. Both SlSFP1 and SlSFP2 were induced by NaCl, cold stress and dehydration. GFP fusion proteins of SlSFP1 and SlSFP2 localized in vacuolar membrane of Arabidopsis cells, suggesting their contribution to sugar accumulation in tomato fruits.