THE ATVAM3 ENCODES A SYNTAXIN-RELATED MOLECULE IMPLICATED IN THE VACUOLAR ASSEMBLY IN ARABIDOPSIS-THALIANA

The vacuole constitutes a large compartment in plant and fungal cells, The VAM3 gene of Saccharomyces cerevisiae encodes a syntaxin-related protein required far vacuolar assembly, An Arabidopsis thaliana cDNA l ibrary, designed for expression iu S. cerevisiae, was screened for cDN As able to complement defective vacuolar assembly of the Delta vam3 mu tation, One cDNA, encoding a 33-kDa protein with structural similariti es to the other syntaxins, was identified, The product of AtVAM3 (AtVa m3p) was expressed in various tissues including roots, leaves, inflore scence stems, flower buds, and young siliques. The AtVAM3 transcripts were abundant; in undifferentiated cells in the meristematic region, A tVam3p fractionated predominantly to an 8,000 x g pellet fraction wher e a vacuolar membrane protein H+-translocating inorganic pyrophosphata se (H+-PPase) also fractionated. Immunoelectron microscopy showed that AtVam3p was localized to restricted regions on the vacuolar membranes , The propose that AtVam3p provides the t-SNARE function in the vacuol ar assembly in A. thaliana.