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 library, designed for expression iu S. cerevisiae, was screened for cDNAs able to complement defective vacuolar assembly of the Delta vam3 mutation, One cDNA, encoding a 33-kDa protein with structural similarities to the other syntaxins, was identified, The product of AtVAM3 (AtVam3p) was expressed in various tissues including roots, leaves, inflorescence stems, flower buds, and young siliques. The AtVAM3 transcripts were abundant; in undifferentiated cells in the meristematic region, AtVam3p fractionated predominantly to an 8,000 x g pellet fraction where a vacuolar membrane protein H+-translocating inorganic pyrophosphatase (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 vacuolar assembly in A. thaliana.