CA2+-Mediated Signal Transduction in Plants

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A new family of Ca2+-dependent protein kinases, called CDPKs, has recently been discovered. CDPKs are unique because they have a novel structure with a kinase domain joined to a Ca2+-binding domain similar to calmodulin. An important long term goal is to understand the function of CDPKs in Ca2+-mediated signal transduction pathways. The model plant system Arabidopsis has been chosen for this purpose. The foundation of the proposal is to determine how Ca2+ regulates CDPK activity. A biochemical and molecular genetic approach will be used to test a model referred to as a "stream-lined version of CaMK II". An E. coli. expression system has been developed to provide functional enzyme for this purpose. Two approaches will be pursued to investigate the biological functions of a specific CDPK isoform: 1) Isoform AK1 and a mutant "unregulated" version of AK1, will be over-expressed in transgenic plants to examine the effects of altering the balance of its activity in vivo. 2) AK1's intracellular location will be determined to provide information on its potential in vivo substrates.