Effect of phosphate nutrition on growth, physiology and phosphate transporter expression of cucumber seedlings.

Although abundantly present in soils, inorganic phosphate (Pi) acquisition by plants is highly dependent on the transmembrane phosphate transporter (PT) gene family. Cucumber (Cucumis sativus) requires a large amount of phosphorus (P). The purpose of this study was to isolate the CsPT2-1 from cucumber roots, and to determine the influence of Pi nutrition on cucumber growth, metabolism and transcript levels of CsPT2-1 in tissues. Full length CsPT2-1 was cloned and phylogenetically identified. In two greenhouse experiments, P-deficient seedlings provided with low or high P concentrations were sampled at 10 and 21 days post treatment, respectively. Addition of P dramatically reduced growth of roots but not shoots. Supplying plants with high P resulted in increased total protein in leaves. Acid phosphatase activity increased significantly in leaves at any rate higher than 4 mM P. Increasing P concentration had a notable decrease in glucose concentrations in leaves of plants supplied with >0.5 mM P. In roots, glucose and starch concentrations increased with increasing P supply. Steady-state transcript levels of CsPT2-1 were high in P-deprived roots, but declined when plants were provided >10 mM P. To our knowledge, this is the first report focusing on a PT and its expression levels in cucumber.