NPCT1, a Golgi apparatus localized determinant of salt tolerance

Abstract

The monogenic recessive mutation npct1-1 isolated by screening an Arabidopsis thaliana population of T-DNA insertion mutants causes NaCl sensitivity of seedlings. The T-DNA is inserted 680 bp upstream of the At5g44370 initiation codon. A second allele npct1-2 was obtained and both npct1-1 and 1-2 seedlings exhibit NaCl sensitivity that is characterized by cessation of terminal root growth, increased lateral branching and swelling of root tips. npct1 seedlings are hyperionic but not hyperosmotic sensitive with differential sensitivity to Cl^- that is greater than to Na⁺ or K⁺. NPCT1 is a member of the Na⁺-dependent inorganic phosphate co-transporter-like-protein family (organic solute co-transporter gene superfamily). Some of these are known as VGLUT (vesicular glutamate transporter) in mammal. A chimeric NPCT1-GFP localized to the Golgi apparatus based on transient expression assay. A salt adaptation function for NPCT1 in xyloglucan deposition to the cell wall is hypothesized.