A full length cDNA of a barley leaf messenger, found to increase in amount during infection attempts by the powdery mildew fungus (Erysiphe graminis), is characterized. The messenger encodes a polypeptide of 261 amino acid residues with a calculated mass of 29.2 kDa and a pl of 4.6. Sequence comparisons as well as serological studies demonstrate that the encoded protein is closely related to a family of mammalian proteins believed to have functions associated with the multifunctional Ca²⁺‐dependent protein kinases. 1992 BIOS Scientific Publishers Ltd