Identification and characterization of GONST1, a Golgi-localized GDP-mannose transporter in Arabidopsis

Transport of nucleotide sugars across the Golgi apparatus membrane is requi red for the luminal synthesis of a variety of plant cell surface components . We identified an Arabidopsis gene encoding a nucleotide sugar transporter (designated GONST1) that we have shown by transient gene expression to be localized to the Golgi. GONST1 complemented a GDP-mannose transport-defecti ve yeast mutant (vrg4-2), and Golgi-rich vesicles from the complemented str ain displayed increased GDP-mannose transport activity. GONST1 promoter::be ta -glucuronidase studies suggested that this gene is expressed ubiquitousl y. The identification of a Golgi-localized nucleotide sugar transporter fro m plants will allow the study of the importance of this class of proteins i n the synthesis of plant cell surface components such as cell wall polysacc harides.