The induction of kin genes in cold-acclimating Arabidopsis thaliana. Evidence of a role for calcium.

The involvement of calcium signaling during cold-induction of the kin genes of Arabidopsis thaliana (L.) Heynh. was examined. Treatments with chemicals which either chelate extracellular calcium (EGTA) or block the plasma-membrane calcium channels (La3+, Gd3+) inhibited cold acclimation as well as kin gene expression. Ruthenium red, an inhibitor of calcium release from intracellular stores partially inhibited kin gene expression and development of freezing tolerance. An inhibitor of calcium-dependent protein kinases (CDPKs) and calmodulin prevented cold acclimation as well as the cold induction of kin genes. Using restriction fragment length polymorphism-coupled domain-directed differential display, five CDPK clones were identified which showed differential regulation by cold. The amplified fragments showed homology to known plant CDPKs. The involvement of calcium and calcium-binding proteins in cold acclimation of A. thaliana is discussed.