Hyperosmotic stress induces a rapid and transient increase in inositol 1,4,5-trisphosphate independent of abscisic acid in arabidopsis cell culture
2001
Takahashi, S. (Institute of Physical and Chemical Research, Wako, Saitama (Japan)) | Katagiri, T. | Hirayama, T. | Yamaguchi Shinozaki, K. | Shinozaki, K.
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 phospboinositide turnover - in hyperosmotic-stress signaling, we analyzed changes in inositol 1, 4, 5-trisphosphate (Ins(1, 4, 5)P3) content in response to hyperos-motic 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 tbe 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 tban 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.
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