Polyamine Transport Systems in Plants

Polyamine (PA) transport has been analyzed at the cell and organ levels in several plant species, but currently the molecular mechanisms of PA transport are not completely understood. Several papers recently identified plant PA transporters. A study of Arabidopsis oxidative stress responses to the herbicide paraquat (PQ) identified a LAT (L-type amino acid transporter) family protein as a transporter of both PQ and PA. Other studies based on yeast complementation analyses revealed that LAT family genes in rice and Arabidopsis function as PA transporters. Arabidopsis LAT proteins exhibited different subcellular localizations, suggesting that these transporters could be involved in both intracellular PA trafficking and PA uptake across the plasma membrane. These results provide novel insights into plant PA transport and explain the mechanism for PA-mediated protection against PQ toxicity. In this review, we focus on recent advances in our understanding of plant PA transport systems and discuss the roles of the recently identified plant PA transporters.