Press Releases
Jun. 13, 2011

How did plants explore unique intracellular trafficking routes?

  • Kazuo Ebine (Department of Biological Sciences, University of Tokyo,
    Current affiliation: Department of Parasitology, National Institute of Infectious Diseases)
  • Takashi Ueda (Department of Biological Sciences, University of Tokyo)


Endosomal trafficking plays an integral role in various eukaryotic cell activities. In animal cells, a member of the RAB GTPase family, RAB5, is known as a key regulator of various endosomal functions, including endosomal fusion, endosomal signaling, and endosomal motility. In addition to orthologs of animal RAB5, land plants harbor the plant-unique RAB5, conserved in all land plant lineages examined thus far. Previously, it was unknown and of much interest why plants evolved two distinct types of RAB5 and how they differed functionally. Plants also acquired the unique machinery for membrane fusion (SNARE protein) during evolution. The presence of plant-specific RAB and SNARE suggested diversification of membrane trafficking pathways was achieved by molecular evolution of RAB and SNARE in a lineage specific manner; however, this has not been demonstrated experimentally. Using Arabidopsis thaliana , we showed the plant-unique RAB5 (ARA6) promotes membrane fusion between endosomes and the plasma membrane, with seed plant-unique R-SNARE (VAMP727) (Figure 1). This pathway has not been described in plant cells thus far. We further demonstrated that ARA6 has a functional role in the salinity stress response. Our results indicate that plants explored a new intracellular trafficking route from endosomes to the plasma membrane during evolution (Figure 2), which plays an important role in responding to environmental cues.

Paper information

Kazuo Ebine1, Masaru Fujimoto1, Yusuke Okatani1, Tomoaki Nishiyama2, Tatsuaki Goh1,7, Emi Ito1, Tomoko Dainobu1, Aiko Nishitani3, Tomohiro Uemura1, Masa H. Sato3, Hans Thordal-Christensen4, Nobuhiro Tsutsumi5, Akihiko Nakano1,6, and Takashi Ueda1

  • 1 Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
  • 2 Advanced Science Research Center, Kanazawa University, 13-1 Takara-machi, Kanazawa, Ishikawa 920-0934, Japan.
  • 3 Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, 1-5, Shimogamo-nakaragi-cho, Sakyo-ku, Kyoto, Kyoto 606-8522, Japan.
  • 4 Department of Agriculture and Ecology, Faculty of Life Sciences, University of Copenhagen Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark.
  • 5 Laboratory of Plant Molecular Genetics, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
  • 6 Molecular Membrane Biology Laboratory, RIKEN Advanced Science Institute, Wako, Saitama 351-0198, Japan.
  • 7 Present address: Department of Biology, Graduate School of Science, Kobe University, Kobe 657-8501, Japan
A membrane trafficking pathway regulated by the plant-specific RAB GTPase ARA6
Nature Cell Biology, Online Edition: 2011 / 6 / 13 (Japan time), doi: 10.1038/ncb2270
Figure 1

Figure 1. Diversification of membrane trafficking pathways in plant cells, which was achieved by acquisition of new RAB and SNARE molecules.

Figure 2

Figure 2. A novel trafficking pathway modulated by ARA6 and VAMP727 was acquired during plant evolution.