Electron tomography of RabA4b- and PI-4Kβ1-labeled trans Golgi network compartments in Arabidopsis

Traffic. 2011 Mar;12(3):313-29. doi: 10.1111/j.1600-0854.2010.01146.x. Epub 2011 Jan 7.

Abstract

The trans Golgi network (TGN) of plant cells sorts and packages Golgi products into secretory (SV) and clathrin-coated (CCV) vesicles. We have analyzed of TGN cisternae in Arabidopsis root meristem cells by cell fractionation and electron microscopy/tomography to establish reliable criteria for identifying TGN cisternae in plant cells, and to define their functional attributes. Transformation of a trans Golgi cisterna into a Golgi-associated TGN cisterna begins with cisternal peeling, the formation of SV buds outside the plane of the cisterna and a 30-35% reduction in cisternal membrane area. Free TGN compartments are defined as cisternae that have detached from the Golgi to become independent organelles. Golgi-associated and free TGN compartments, but not trans Golgi cisternae, bind anti-RabA4b and anti-phosphatidylinositol-4 kinase (PI-4K) antibodies. RabA4b and PI-4Kβ1 localize to budding SVs in the TGN and to SVs en route to the cell surface. SV and CCV release occurs simultaneously via cisternal fragmentation, which typically yields ∼30 vesicles and one to four residual cisternal fragments. Early endosomal markers, VHA-a1-green fluorescent protein (GFP) and SYP61-cyan fluorescent protein (CFP), colocalized with RabA4b in TGN cisternae, suggesting that the secretory and endocytic pathways converge at the TGN. pi4k1/pi4k2 knockout mutant plants produce SVs with highly variable sizes indicating that PI-4Kβ1/2 regulates SV size.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • 1-Phosphatidylinositol 4-Kinase / genetics
  • 1-Phosphatidylinositol 4-Kinase / metabolism*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Arabidopsis* / enzymology
  • Arabidopsis* / ultrastructure
  • Cell Membrane / ultrastructure
  • Cell Wall / chemistry
  • Cell Wall / metabolism
  • Cell Wall / ultrastructure
  • Cytokinesis / physiology
  • Electron Microscope Tomography*
  • Gene Knockout Techniques
  • Immunohistochemistry
  • Mutation
  • Plant Roots / enzymology
  • Plant Roots / ultrastructure
  • Polysaccharides / analysis
  • Secretory Vesicles / ultrastructure
  • rab4 GTP-Binding Proteins / genetics
  • rab4 GTP-Binding Proteins / metabolism*
  • trans-Golgi Network / chemistry
  • trans-Golgi Network / ultrastructure

Substances

  • Arabidopsis Proteins
  • Polysaccharides
  • 1-Phosphatidylinositol 4-Kinase
  • rab4 GTP-Binding Proteins