Peter Olsson

Calmodulin is a Ca2+-dependent regulatory protein in eukaryotic cells involved in a variety of intracellular activities. Many responses to abiotic stresses involve signaling by Ca2+ and Ca2+/calmodulin regulation, including water and salinity stress. To investigate how calmodulin affects germination on media with high concentrations of NaCl, transgenic tobacco plants expressing heterologous calmodulin were generated and characterized. Transgenic tobacco seeds showed significantly shortened germination times on media containing varying salt (120-160 mM) and calcium (3 and 13 mM) concentrations, compared to control seeds. Using media containing 140 mM NaCl and 13 mM CaCl2, the average germination time was shortened by 2-3 days compared to control (P < 0.05). In addition, the germinating transgenic seeds contained higher transient levels of gamma-aminobutyric acid compared to control seeds (P < 0.05). The tobacco Ca2+/calmodulin-regulated glutamate decarboxylase, synthesizing gamma-aminobutyric acid may therefore be stimulated by the heterologous calmodulin. (C) 2004 Elsevier Ireland Ltd. All rights reserved.