An Abscisic Acid-Activated and Calcium-Independent Protein Kinase from Guard Cells of Fava Bean

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Abstract

Abscisic acid (ABA) regulation of stomatal aperture is known to involve both Ca2+-dependent and Ca2+-independent signal transduction pathways. Electrophysiological studies suggest that protein phosphorylation is involved in ABA action in guard cells. Using biochemical approaches, we identified an ABA-activated and Ca2+-independent protein kinase (AAPK) from guard cell protoplasts of fava bean. Autophosphorylation of AAPK was rapidly (∼1 min) activated by ABA in a Ca2+-independent manner. ABA-activated autophosphorylation of AAPK occurred on serine but not on tyrosine residues and appeared to be guard cell specific. AAPK phosphorylated histone type III-S on serine and tnreonine residues, and its activity toward histone type III-S was markedly stimulated in ABA-treated guard cell protoplasts. Our results suggest that AAPK may play an important role in the Ca2+-independent ABA signaling pathways of guard cells.

Original languageEnglish (US)
Pages (from-to)2359-2368
Number of pages10
JournalPlant Cell
Volume8
Issue number12
DOIs
StatePublished - Dec 1996

All Science Journal Classification (ASJC) codes

  • Plant Science
  • Cell Biology

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