1. Reproduction et Développement des Plantes, IFR128 BioSciences Lyon-Gerland, Centre National de la Recherche Scientifique, Institut National de la Recherche Agronomique, Université Claude Bernard Lyon I, Ecole Normale Supérieure de Lyon, 46 allée d'Italie, 69364 Lyon Cedex 07, France

Correspondence to: Thierry Gaude¹ Correspondence and requests for materials should be addressed to T.G. (Email: thierry.gaude@ens-lyon.fr).

Abstract

Polarized cellular distribution of the phytohormone auxin and its carriers is essential for normal plant growth and development. Polar auxin transport ^{1, 2} is maintained by a network of auxin influx (AUX)³ and efflux (PIN)^{1, 2, 4, 5, 6} carriers. Both auxin transport and PIN protein cycling between the plasma membrane and endosomes require the activity of the endosomal GNOM^{1, 2, 7, 8}; however, intracellular routes taken by these carriers remain largely unknown. Here we show that Arabidopsis thaliana SORTING NEXIN 1 (AtSNX1) is involved in the auxin pathway and that PIN2, but not PIN1 or AUX1, is transported through AtSNX1-containing endosomes. We demonstrate that the snx1-null mutant exhibits multiple auxin-related defects and that loss of function of AtSNX1 severely enhances the phenotype of a weak gnom mutant. In root cells, we further show that AtSNX1 localizes to an endosomal compartment distinct from GNOM-containing endosomes, and that PIN2 accumulates in this compartment after treatment with the phosphatidylinositol-3-OH kinase inhibitor wortmannin or after a gravity stimulus. Our data reveal the existence of a novel endosomal compartment involved in PIN2 endocytic sorting and plant development.

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