An ARF-GEF acting at the Golgi and in selective endocytosis in polarized plant cells : Abstract : Nature

Nature 448, 493-496 (26 July 2007) | doi:10.1038/nature06023; Received 27 February 2007; Accepted 11 June 2007

An ARF-GEF acting at the Golgi and in selective endocytosis in polarized plant cells

Ooi-kock Teh¹ & Ian Moore¹

Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK

Correspondence to: Ian Moore¹ Correspondence and requests for materials should be addressed to I.M. (Email: ian.moore@plants.ox.ac.uk).

Circumstantial evidence suggests that intracellular membrane trafficking pathways diversified independently in the plant kingdom^1,^2,^3,^4,^5,^6,^7,^8,^9,¹⁰, but documented examples are rare^6,^11,¹². ARF-GEFs (guanine-nucleotide exchange factors for ADP-ribosylation factor GTPases) are essential for vesicular trafficking in all eukaryotic kingdoms, but of the eight ARF-GEF families, only the ancestral BIG and GBF types are found in plants^1,². Whereas fungal and animal GBF proteins perform conserved functions at the Golgi, the Arabidopsis thaliana GBF protein GNOM is thought to act in only the process of recycling from endosomes^3,^4,⁵. We now show that the related Arabidopsis GBF protein GNOM-LIKE1 (GNL1) has an ancestral function at the Golgi but is also required for selective internalization from the plasma membrane in the presence of brefeldin A (BFA). We identified gnl1 mutants that accumulated biosynthetic and recycling endoplasmic reticulum markers in enlarged internal compartments. Notably, in the absence of functional GNL1, Golgi stacks were rendered sensitive to the selective ARF-GEF inhibitor BFA, which caused them to fuse with the endoplasmic reticulum. Furthermore, in BFA-treated gnl1 roots, the internalization of a polar plasma-membrane marker, the auxin efflux carrier PIN2, was selectively inhibited. Thus, GNL1 is a BFA-resistant GBF protein that functions with a BFA-sensitive ARF-GEF both at the Golgi and in selective endocytosis, but not in recycling from endosomes. We propose that the evolution of endocytic trafficking in plants was accompanied by neofunctionalization within the GBF family, whereas in other kingdoms it occurred independently by elaboration of additional ARF-GEF families.

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