摘要
IN recent years, calmodulin （CaM）, an important Ca<sup>2+</sup> receptor and constituent of cellular signal transduction systems, has been found extracellularly. We have verified that CaM is presented extracellularly in all of plant species we have examined. In addition, we have reported that extracellular CaM has some biological significance, such as stimulation of cell proliferation, cell wall regeneration, initiation of pollen germination and tube growth and inducement of rbcS gene expression. The role of heterotrimeric G proteins in pollen germination, tube growth and signal transduction of extracellular CaM has been examined in Lily pollen, and two kinds of antibodies against animal Gzα internal sequence and N-terminal
