AUX1 (source code)
= AUX1
{c}
\b[AUX1] is a plant <membrane protein> that promotes uptake of the <auxin> <indole-3-acetic acid> into cells. It is an influx carrier: its role concerns entry across a <cell membrane>, whereas the distribution of <auxin> through a tissue also depends on export, cellular geometry and the placement of transporters. These distinctions connect a molecular uptake mechanism to <polar auxin transport> without treating one carrier as the whole tissue-level pathway.<High-affinity auxin transport by the AUX1 influx carrier protein by Yaodong Yang and others>[Abstract: functional identification of AUX1-mediated auxin influx.]{ref}
Direct transport evidence came from expressing AUX1 in Xenopus oocytes and measuring uptake of tritium-labeled <indole-3-acetic acid>. Uptake was saturable and pH-dependent. Saturation matters: increasing substrate cannot increase a finite population of carrier-mediated transport events without bound. Dependence on pH connects uptake to the chemical environment across the <biological membrane>, rather than to AUX1 abundance alone.<High-affinity auxin transport by the AUX1 influx carrier protein by Yaodong Yang and others>[Oocyte expression and radiolabeled IAA uptake assay.]{ref}
In <Arabidopsis thaliana> roots, <Ranjan Swarup> and collaborators localized AUX1 and compared transport-related mutant phenotypes using different <auxin> compounds. Their results supported distinct routes for hormone delivery and redistribution near the root apex. The combination is instructive: localization asks where a carrier operates; heterologous expression tests what it can transport. Neither measurement alone completely specifies the resulting <auxin> pattern in an intact root.<Localization of the auxin permease AUX1 suggests two functionally distinct hormone transport pathways operate in the Arabidopsis root apex by Ranjan Swarup and others>[Genes & Development 15 (2001), 2648–2653; localization and Figure 3 mutant/auxin comparisons.]{ref}
Back to article page
