and
directional, intercellular auxin transport (Petrásek et al., 2006;
Grunewald and Friml, 2010). The polar auxin transport has an
essential role in most auxin-regulated processes and is mediated by
homologues of the ATP Binding Cassette subgroup B (ABCB) multiple
drug resistance transporters (Geisler et al., 2005), by auxin
influx proteins of the AUX1/LAX family (Swarup et al., 2008) and
by PIN-formed (PIN) auxin efflux proteins (Petrásek ˇ and Friml,
2009).