A Golgi-Released Subpopulation of the Trans-Golgi Network Mediates Protein Secretion in Arabidopsis

Plant Physiol. 2019 Feb;179(2):519-532. doi: 10.1104/pp.18.01228. Epub 2018 Dec 13.


Spatiotemporal coordination of protein trafficking among organelles is essential for eukaryotic cells. The post-Golgi interface, including the trans-Golgi network (TGN), is a pivotal hub for multiple trafficking pathways. The Golgi-released independent TGN (GI-TGN) is a compartment described only in plant cells, and its cellular and physiological roles remain elusive. In Arabidopsis (Arabidopsis thaliana), the SYNTAXIN OF PLANTS (SYP) 4 group Qa-SNARE (soluble N-ethylmaleimide) membrane fusion proteins are shared components of TGN and GI-TGN and regulate secretory and vacuolar transport. Here we reveal that GI-TGNs mediate the transport of the R-SNARE VESICLE-ASSOCIATED MEMBRANE PROTEIN (VAMP) 721 to the plasma membrane. In interactions with a nonadapted powdery mildew pathogen, the SYP4 group of SNAREs is required for the dynamic relocation of VAMP721 to plant-fungus contact sites via GI-TGNs, thereby facilitating complex formation with its cognate SNARE partner PENETRATION1 to restrict pathogen entry. Furthermore, quantitative proteomic analysis of leaf apoplastic fluid revealed constitutive and pathogen-inducible secretion of cell wall-modification enzymes in a SYP4- and VAMP721-dependent manner. Hence, the GI-TGN acts as a transit compartment between the Golgi apparatus and the plasma membrane. We propose a model in which the GA-TGN matures into the GI-TGN and then into secretory vesicles by increasing the abundance of VAMP721-dependent secretory pathway components.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / genetics
  • Arabidopsis / metabolism*
  • Arabidopsis / microbiology
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Ascomycota / pathogenicity
  • Cell Membrane / metabolism
  • Cell Wall / metabolism
  • Enzymes / metabolism
  • Golgi Apparatus / metabolism*
  • Host-Pathogen Interactions / physiology
  • Mutation
  • Plant Diseases / microbiology
  • Plant Leaves / metabolism
  • Plant Leaves / microbiology
  • Plants, Genetically Modified
  • R-SNARE Proteins / genetics
  • R-SNARE Proteins / metabolism*
  • SNARE Proteins / genetics
  • SNARE Proteins / metabolism
  • trans-Golgi Network / metabolism


  • Arabidopsis Proteins
  • Enzymes
  • R-SNARE Proteins
  • SNARE Proteins
  • VAMP721 protein, Arabidopsis