Auxin and heat shock activation of a novel member of the calmodulin like domain protein kinase gene family in cultured alfalfa cells

A calmodulin like domain protein kinase (CPK) homologue was identified in a lfalfa and termed MsCPK3. The full-length sequence of cDNA encoded a 535 am ino acid polypeptide with a molecular weight of 60.2 kDa. The deduced amino acid sequence showed all the conserved motifs that define other members of this kinase family, such as serine-threonine kinase domain, a junction reg ion and four potential Ca2+-binding EF sites. The recombinant MsCPK3 protei n purified from E. coli was activated by Ca2+ and inhibited by calmodulin a ntagonist (W-7) in vitro phosphorylation assays. The expression of MsCPK3 g ene increased in the early phase of the 2,4-D induced alfalfa somatic embry ogenesis. Heat shock also activated this gene while kinetin, ABA and NaCl t reatment did not result in MsCPK3 mRNA accumulation. The data presented sug gest that the new alfalfa CPK differs in stress responses from the previous ly described homologues and in its potential involvement in hormone and str ess-activated reprogramming of developmental pathways during somatic embryo genesis.