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Evidence for a sorting endosome in Arabidopsis root cells

Jaillais, Yvon, Fobis-Loisy, Isabelle, Miège, Christine, Gaude, Thierry
Plant journal 2008 v.53 no.2 pp. 237-247
Arabidopsis, animals, drugs, endosomes, eukaryotic cells, lysosomes, plasma membrane, protein transport, proteins, recycling, vacuoles, yeasts
In eukaryotic cells, the endocytic and secretory pathways are key players in several physiological processes. These pathways are largely inter-connected in animal and yeast cells through organelles named sorting endosomes. Sorting endosomes are multi-vesicular compartments that redirect proteins towards various destinations, such as the lysosomes or vacuoles for degradation, the trans-Golgi network for retrograde transport and the plasma membrane for recycling. In contrast, cross-talk between the endocytic and secretory pathways has not been clearly established in plants, especially in terms of cargo protein trafficking. Here we show by co-localization analyses that endosomes labelled with the AtSORTING NEXIN1 (AtSNX1) protein overlap with the pre-vacuolar compartment in Arabidopsis root cells. In addition, alteration of the routing functions of AtSNX1 endosomes by drug treatments leads to mis-routing of endocytic and secretory cargo proteins. Based on these results, we propose that the AtSNX1 endosomal compartment represents a sorting endosome in root cells, and that this specialized organelle is conserved throughout eukaryotes.