CA2-DEPENDENT PROTEIN-KINASES AND STRESS SIGNAL-TRANSDUCTION IN PLANTS()

Stress responses in plants involve changes in the transcription of spe cific genes. The constitutively active mutants of two related Ca2+-dep endent protein kinases (CDPK1 and CDPK1a) activate a stress-inducible promoter, bypassing stress signals. Six other plant protein kinases, i ncluding two distinct CDPKs, fail to mimic this stress signaling, The activation is abolished by a CDPK1 mutation in the kinase domain and d iminished by a constitutively active protein phosphatase 2C that is ca pable of blocking responses to the stress hormone abscisic acid. A var iety of functions are mediated by different CDPKs. CDPK1 and CDPK1a ma y be positive regulators controlling stress signal transduction in pla nts.