Hyperosmotic stress induces a rapid and transient increase in inositol 1,4,5-trisphosphate independent of abscisic acid in Arabidopsis cell culture.
Phospholipid metabolism is involved in hyperosmotic-stress responses in plants. To investigate the role of phosphoinositide-specific phospholipase C (PI-PLC)-a key enzyme in phosphoinositide turnover-in hyperosmotic-stress signaling, we analyzed changes in inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) content in response to hyperosmotic shock or salinity in Arabidopsis thaliana T87 cultured cells. Within a few s, a hyperosmotic shock, caused by mannitol, NaCl, or dehydration, induced a rapid and transient increase in Ins(1,4,5)P3. However, no transient increase was detected in cells treated with ABA. Neomycin and U73122, inhibitors of PI-PLC, inhibited the increase in Ins(1,4,5)P3 caused by the hyperosmotic shock. A rapid increase in phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) in response to the hyperosmotic shock also occurred, but the rate of increase was much slower than that of Ins(1,4,5)P3. These findings indicate that the transient Ins(1,4,5)P3 production was due to the activation of PI-PLC in response to hyperosmotic stress. PI-PLC inhibitors also inhibited hyperosmotic stress-responsive expression of some dehydration-inducible genes, such as rd29A (lti78/cor78) and rd17 (cor47), that are controlled by the DRE/CRT cis-acting element but did not inhibit hyperosmotic stress-responsive expression of ABA-inducible genes, such as rd20. Taken together, these results suggest the involvement of PI-PLC and Ins(1,4,5)P3 in an ABA-independent hyperosmotic-stress signal transduction pathway in higher plants.
Laboratory of Plant Molecular Biology, RIKEN Tsukuba Institute, 3-1-1 Koyadai, Tsukuba, Ibaraki, 305-0074 Japan.
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S
Takahashi
T
T
Katagiri
T
T
Hirayama
K
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Yamaguchi-Shinozaki
K
K
Shinozaki
D000040:Abscisic Acid / Q000378:metabolism* / Q000494:pharmacology; D017360:Arabidopsis; D029681:Arabidopsis Proteins; D002135:Calcium-Binding Proteins / Q000235:genetics; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D015870:Gene Expression; D017343:Genes, Plant; D015544:Inositol 1,4,5-Trisphosphate / Q000096:biosynthesis*; D009355:Neomycin / Q000494:pharmacology; D009997:Osmotic Pressure; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000096:biosynthesis; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D054801:Phosphoinositide Phospholipase C; D011760:Pyrrolidinones / Q000494:pharmacology; D013997:Time Factors; D014157:Transcription Factors / Q000235:genetics; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors*
D029681:Arabidopsis Proteins; D002135:Calcium-Binding Proteins; C114579:DREB2A protein, Arabidopsis; D004791:Enzyme Inhibitors; D004963:Estrenes; D019269:Phosphatidylinositol 4,5-Diphosphate; D011760:Pyrrolidinones; C417972:RD20 protein, Arabidopsis; D014157:Transcription Factors; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D000040:Abscisic Acid; D015544:Inositol 1,4,5-Trisphosphate; D010738:Type C Phospholipases; D054801:Phosphoinositide Phospholipase C; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D009355:Neomycin