Abstract
Arabidopsis genome contains many ABC protein genes. P-glycoprotein-like (PGP) subfamily has been drawing attentions of plant hormone researchers concerning the auxin transport activity. In this study, we analyzed the gene expression and function of AtPGP4, a PGP type ABC protein. The AtPGP4 expression was up-regulated by both auxin and cytokinin. AtPGP4 promoter::GUS transgenic plants showed that AtPGP4 was strongly expressed in the root, and limited mainly to epidermal cells. AtPGP4 was localized at the plasma membrane, which was proved by sucrose density gradient fractionation and immunoblotting. The localization of AtPGP4 was also supported by immunolocalization analysis. The root development of atpgp4 mutants was clearly reduced compared to the wild type. Atpgp4 mutants displayed reduced basipetal auxin transport, whereas AtPGP4 overexpressing seedlings showed a substantial increase in basipetal auxin transport. We are now analyzing this transport activity more in detail.
