The ABC of Phytohormone Translocation

ATP-driven transport across biological membranes is a key process to translocate solutes from the interior of the cell to the extracellular environment. In humans, ATP-binding cassette transporters are involved in absorption, distribution, metabolism, excretion, and toxicity, and also play a major role in anticancer drug resistance. Analogous transporters are also known to be involved in phytohormone translocation. These include, e.g., the transport of auxin by ABCB1/19 in Arabidopsis thaliana, the transport of abscisic acid by AtABCG25, and the transport of strigolactone by the Petunia hybrida ABC transporter PDR1. Within this article, we outline the current knowledge about plant ABC transporters with respect to their structure and function, and provide, for the first time, a protein homology model of the strigolactone transporter PDR1 from P. hybrida.