Calcium-Independent Activation of Salicylic Acid-Induced Protein Kinase and a 40-Kilodalton Protein Kinase by Hyperosmotic Stress1

AUTOR(ES)

Hoyos, Mary Elizabeth

FONTE

American Society of Plant Physiologists

RESUMO

Reversible protein phosphorylation/dephosphorylation plays important roles in signaling the plant adaptive responses to salinity/drought stresses. Two protein kinases with molecular masses of 48 and 40 kD are activated in tobacco cells exposed to NaCl. The 48-kD protein kinase was identified as SIPK (salicylic acid-induced protein kinase), a member of the tobacco MAPK (mitogen-activated protein kinase) family that is activated by various other stress stimuli. The activation of the 40-kD protein kinase is rapid and dose-dependent. Other osmolytes such as Pro and sorbitol activate these two kinases with similar kinetics. The activation of 40-kD protein kinase is specific for hyperosmotic stress, as hypotonic stress does not activate it. Therefore, this 40-kD kinase was named HOSAK (high osmotic stress-activated kinase). HOSAK is a Ca2+-independent kinase and uses myelin basic protein (MBP) and histone equally well as substrates. The kinase inhibitor K252a rapidly activates HOSAK in tobacco cells, implicating a dephosphorylation mechanism for HOSAK activation. Activation of both SIPK and HOSAK by high osmotic stress is Ca2+ and abscisic acid (ABA) independent. Furthermore, mutation in SOS3 locus does not affect the activation of either kinase in Arabidopsis seedlings. These results suggest that SIPK and 40-kD HOSAK are two new components in a Ca2+- and ABA-independent pathway that may lead to plant adaptation to hyperosmotic stress.

Documentos Relacionados

• Osmotic Stress Induces Rapid Activation of a Salicylic Acid–Induced Protein Kinase and a Homolog of Protein Kinase ASK1 in Tobacco Cells
• Activation of Salicylic Acid–Induced Protein Kinase, a Mitogen-Activated Protein Kinase, Induces Multiple Defense Responses in Tobacco
• An Abscisic Acid-Activated and Calcium-Independent Protein Kinase from Guard Cells of Fava Bean.
• Calcium-independent activation of endothelial nitric oxide synthase by ceramide
• Analysis of stress-induced or salicylic acid-induced expression of the pathogenesis-related 1a protein gene in transgenic tobacco.