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Proc Natl Acad Sci U S A. 2018 Mar 6;115(10):E2457-E2466. doi: 10.1073/pnas.1717839115. Epub 2018 Feb 20.

Distinct sets of tethering complexes, SNARE complexes, and Rab GTPases mediate membrane fusion at the vacuole in Arabidopsis.

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Division of Cellular Dynamics, National Institute for Basic Biology, 444-8585 Okazaki, Aichi, Japan.
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 113-0033 Tokyo, Japan.
Department of Basic Biology, SOKENDAI (Graduate University for Advanced Studies), 444-8585 Okazaki, Aichi, Japan.
Department of Plant Developmental Biology, Centre for Organismal Studies, Heidelberg University, 69120 Heidelberg, Germany.
Department of Natural Sciences, International Christian University, 181-8585 Tokyo, Japan.
Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, 630-0192 Nara, Japan.
Live Cell Super-Resolution Imaging Research Team, RIKEN Center for Advanced Photonics, Wako, 351-0198 Saitama, Japan.
Division of Cellular Dynamics, National Institute for Basic Biology, 444-8585 Okazaki, Aichi, Japan;


Membrane trafficking plays pivotal roles in various cellular activities and higher-order functions of eukaryotes and requires tethering factors to mediate contact between transport intermediates and target membranes. Two evolutionarily conserved tethering complexes, homotypic fusion and protein sorting (HOPS) and class C core vacuole/endosome tethering (CORVET), are known to act in endosomal/vacuolar transport in yeast and animals. Both complexes share a core subcomplex consisting of Vps11, Vps18, Vps16, and Vps33, and in addition to this core, HOPS contains Vps39 and Vps41, whereas CORVET contains Vps3 and Vps8. HOPS and CORVET subunits are also conserved in the model plant Arabidopsis. However, vacuolar trafficking in plants occurs through multiple unique transport pathways, and how these conserved tethering complexes mediate endosomal/vacuolar transport in plants has remained elusive. In this study, we investigated the functions of VPS18, VPS3, and VPS39, which are core complex, CORVET-specific, and HOPS-specific subunits, respectively. Impairment of these tethering proteins resulted in embryonic lethality, distinctly altering vacuolar morphology and perturbing transport of a vacuolar membrane protein. CORVET interacted with canonical RAB5 and a plant-specific R-soluble NSF attachment protein receptor (SNARE), VAMP727, which mediates fusion between endosomes and the vacuole, whereas HOPS interacted with RAB7 and another R-SNARE, VAMP713, which likely mediates homotypic vacuolar fusion. These results indicate that CORVET and HOPS act in distinct vacuolar trafficking pathways in plant cells, unlike those of nonplant systems that involve sequential action of these tethering complexes during vacuolar/lysosomal trafficking. These results highlight a unique diversification of vacuolar/lysosomal transport that arose during plant evolution, using evolutionarily conserved tethering components.


CORVET; HOPS; RAB GTPase; SNARE; vacuolar transport

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