Phosphorylation of MAP kinase-like proteins mediate the response of the halotolerant alga Dunaliella viridis to hypertonic shock.
The microalga Dunaliella viridis has the ability to adapt to a variety of environmental stresses including osmotic and thermal shocks, UV irradiation and nitrogen starvation. Lacking a rigid cell wall, Dunaliella provides an excellent model to study stress signaling in eukaryotic unicellular organisms. When exposed to hyperosmotic stress, UV irradiation or high temperature, a 57-kDa protein is recognized by antibodies specific to mammalian p38, to its yeast homologue Hog1, and to the phospho-p38 MAP kinase motif. This 57-kDa protein appears to be both up-regulated and phosphorylated. Three other proteins (50, 45, 43 kDa) were transiently phosphorylated under stress conditions as detected with an antibody specific to the mammalian phospho c-Jun N-terminal kinase (JNK) motif. Treatment with specific inhibitors of p38 MAP kinase (SB203580) and JNK (SP600125) activities markedly impaired the adaptation of Dunaliella to osmotic stress. From an evolutionary standpoint, these data strongly suggest that MAP kinase signaling pathways, other than ERK, were already operating in the common ancestor of plant and animal kingdoms, probably as early as 1400 million years ago.
Jiménez
Carlos
C
Department of Ecology, Faculty of Science, University of Málaga, Málaga 29071, Spain.
Berl
Tomas
T
Rivard
Christopher J
CJ
Edelstein
Charles L
CL
Capasso
Juan M
JM
D000222:Adaptation, Physiological; D000906:Antibodies / Q000276:immunology; D001345:Autoradiography; D002478:Cells, Cultured; D000460:Chlorophyta / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000378:metabolism; D006358:Hot Temperature; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors / Q000276:immunology; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*; D009997:Osmotic Pressure; D010761:Phosphorus Radioisotopes; D010766:Phosphorylation; D012462:Saline Solution, Hypertonic; D014466:Ultraviolet Rays; D048051:p38 Mitogen-Activated Protein Kinases
D000906:Antibodies; D006360:Heat-Shock Proteins; D010761:Phosphorus Radioisotopes; D012462:Saline Solution, Hypertonic; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases