Vacuolar membrane dynamics revealed by GFP-AtVam3 fusion protein.
BACKGROUND
The plant vacuole is a multifunctional organelle that has various physiological functions. The vacuole dynamically changes its function and shape, dependent on developmental and physiological conditions. Our current understanding of the dynamic processes of vacuolar morphogenesis has suffered from the lack of a marker for observing these processes in living cells.


RESULTS
We have developed transgenic Arabidopsis thaliana expressing a vacuolar syntaxin-related molecule (AtVam3/SYP22) fused with green fluorescent protein (GFP). Observations using confocal laser scanning microscopy demonstrated that the plant vacuole contained a dynamic membrane system that underwent a complex architectural remodelling. Three-dimensional reconstitution and time-lapse analysis of GFP-fluorescence images revealed that cylindrical and sheet-like structures were present in the vacuolar lumen and were moving dynamically. The movement, but not the structure itself, was abolished by cytochalasin D, an inhibitor of actin polymerization. This moving structure, which sometimes penetrated through the vacuolar lumen, possessed a dynamic membrane architecture similar to the previously recognized "transvacuolar strand."


CONCLUSIONS
We propose two possible models for the formation of the vacuolar lumenal structure. Membrane structures including protruding tubules and reticular networks have recently been recognized in many other organelles, and may be actively involved in intra- and/or inter-organelle signalling.
Uemura
Tomohiro
T
Graduate School of Biostudies, Kyoto University, Yoshida Nihonmatsu-cho, Sakyo-ku, Kyoto 606-8501, Japan.
Yoshimura
Shige H
SH
Takeyasu
Kunio
K
Sato
Masa H
MH
D017360:Arabidopsis; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology*; D015638:Cytochalasin D / Q000494:pharmacology; D049452:Green Fluorescent Proteins; D007425:Intracellular Membranes / Q000502:physiology*; D008164:Luminescent Proteins / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D018613:Microscopy, Confocal; D009997:Osmotic Pressure; D030821:Plants, Genetically Modified; D050765:Qa-SNARE Proteins; D015398:Signal Transduction; D014617:Vacuoles / Q000502:physiology*
D029681:Arabidopsis Proteins; D008164:Luminescent Proteins; D008565:Membrane Proteins; D050765:Qa-SNARE Proteins; C108430:Vam3 protein, Arabidopsis; D049452:Green Fluorescent Proteins; D015638:Cytochalasin D