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Plant Cell. 2000 Jan;12(1):165-78.

Osmotic stress induces rapid activation of a salicylic acid-induced protein kinase and a homolog of protein kinase ASK1 in tobacco cells.

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  • 1Institute of Biochemistry and Biophysics, Polish Academy of Sciences, ul. Pawińskiego 5a, 02-106 Warsaw, Poland.

Erratum in

  • Plant Cell 2000 Apr;12(4):611.


In tobacco cells, osmotic stress induced the rapid activation of two protein kinases that phosphorylate myelin basic protein. Immunological studies demonstrated that the 48-kD kinase is the salicylic acid-induced protein kinase (SIPK), a member of the mitogen-activated protein kinase family. SIPK was activated 5 to 10 min after the cells were exposed to osmotic stresses, and its activity persisted for approximately 30 min. In contrast, the 42-kD kinase was activated within 1 min after osmotic stress, and its activity was maintained for approximately 2 hr. Moreover, in addition to myelin basic protein, the 42-kD kinase phosphorylated casein and two transcription factors, c-Jun and ATF-2. This latter enzyme was inactivated by a serine/threonine-specific phosphatase but, unlike SIPK, was not affected by a tyrosine-specific phosphatase. After the 42-kD kinase was purified to apparent homogeneity, tryptic peptide analysis indicated that it is a homolog of Arabidopsis serine/threonine kinase1 (ASK1).

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