Abstract
We studied expression of five aquaporin isoforms belonging to TIPs and NIPs in barley (Hordium vulgare) by a quantitative realtime RT-PCR. Seedlings were exposed to various abiotic stresses and phytohormones for 24 h. Treatment with NaCl, ABA and GA differentially regulated the expression of the aquaporin genes. Nitrogen-deficiency down regulated expression of all the genes except HvTIP4;1 in roots, not shoots. Intriguingly, gene expression was restored three days after N was supplied. Heavy metals (Cd, Cu, Zn and Cr) down regulated both the rate of transpiration and the aquaporin genes expression including HvPIP2;1 in roots, indicating that these metals inhibit water uptake activity by decreasing the abundance of water channel proteins. Hg treatment decreased the rate of transpiration but did not suppress gene expression. This inhibition probably involves a direct interaction of Hg with water channel proteins. Functional analysis of the aquaporin genes is ongoing.
