title: Evidence that abscisic acid promotes degradation of SNF1-related protein kinase (SnRK) 1 in wheat and activation of a putative calcium-dependent SnRK2.
abstract: Sucrose nonfermenting-1 (SNF1)-related protein kinases (SnRKs) form a major family of signalling proteins in plants and have been associated with metabolic regulation and stress responses. They comprise three subfamilies: SnRK1, SnRK2, and SnRK3. SnRK1 plays a major role in the regulation of carbon metabolism and energy status, while SnRKs 2 and 3 have been implicated in stress and abscisic acid (ABA)-mediated signalling pathways. The burgeoning and divergence of this family of protein kinases in plants may have occurred to enable cross-talk between metabolic and stress signalling, and ABA-response-element-binding proteins (AREBPs), a family of transcription factors, have been shown to be substrates for members of all three subfamilies. In this study, levels of SnRK1 protein were shown to decline dramatically in wheat roots in response to ABA treatment, although the amount of phosphorylated (active) SnRK1 remained constant. Multiple SnRK2-type protein kinases were detectable in the root extracts and showed differential responses to ABA treatment. They included a 42 kDa protein that appeared to reduce in response to 3 h of ABA treatment but to recover after longer treatment. There was a clear increase in phosphorylation of this SnRK2 in response to the ABA treatment. Fractions containing this 42 kDa SnRK2 were shown to phosphorylate synthetic peptides with amino acid sequences based on those of conserved phosphorylation sites in AREBPs. The activity increased 8-fold with the addition of calcium chloride, indicating that it is calcium-dependent. The activity assigned to the 42 kDa SnRK2 also phosphorylated a heterologously expressed wheat AREBP.
authors: Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México, Distrito Federal 04510, Mexico.
authors: Patricia
authors: P
authors: Coello
authors: Emi
authors: E
authors: Hirano
authors: Sandra J
authors: SJ
authors: Hey
authors: Nira
authors: N
authors: Muttucumaru
authors: Eleazar
authors: E
authors: Martinez-Barajas
authors: Martin A J
authors: MA
authors: Parry
authors: Nigel G
authors: NG
authors: Halford
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology*; D000595:Amino Acid Sequence; D002122:Calcium Chloride / Q000494:pharmacology*; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D010766:Phosphorylation; D010940:Plant Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D059748:Proteolysis / Q000187:drug effects*; D016415:Sequence Alignment; D015398:Signal Transduction / Q000502:physiology*; D013312:Stress, Physiological; D014908:Triticum / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000502:physiology*
chemical_list: D010940:Plant Proteins; D000040:Abscisic Acid; C071570:SNF1-related protein kinases; D017346:Protein Serine-Threonine Kinases; D002122:Calcium Chloride