Protein kinases induced by osmotic stresses and elicitor molecules in tobacco cell suspensions: two crossroad MAP kinases and one osmoregulation-specific protein kinase

Tao protein kinases displaying mitogen-activated protein kinase (MAPK) prop erties are activated both by an hypoosmotic stress and by oligogalacturonid es in tobacco cell suspensions [Cazale et al, (1999) Plane J. 19, 297-307]. Using specific antibodies, they mere identified as the salicylic acid-indu ced protein kinase (SIPK) and wound-induced protein kinase (WIPK). The SIPK was also activated by an hyperosmotic stress, indicating that the same kin ase may play a role both in hypo- and hyperosmotic signalling pathways, in addition to its involvement in the transduction of elicitor signals, Using immunoprecipitation followed by two-dimensional in-gel kinase assay, three molecular forms of the SIPK were observed, suggesting that additional modif ications of the activated kinase may occur. In contrast to WIPK and SIPK, w hich are located at the crossroad of several transduction pathways initiate d by elicitor or osmotic stimuli, a 44 kDa kinase, that mould not belong to the MAPK family, appeared more specific to osmotic stress. (C) 2000 Federa tion of European Biochemical Societies.