The polyphosphoinositides,phosphatidylinositol monophosphate and phosphatidylinositol bisphosphate,are present in nuclei isolated from carrot protoplast |
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Authors: | Keith W Hendrix Hanna Assefa Wendy F Boss |
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Institution: | (1) Department of Botany, North Carolina State University, Raleigh, North Carolina |
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Abstract: | Summary Nuclei were isolated from carrot protoplasts and the distribution of 3H]inositol-labeled phospholipids was analyzed by thinlayer chromatography. Phosphatidylinositol (PI), lysophos-phatidylinositol (LPI), phosphatidylinositol monophosphate (PIP), lysophosphatidylinositol monophosphate (LPIP), and phosphatidylinositol bisphosphate (PIP2) were 55.7%, 12.3%, 5.0%, 11.5%, and 3.6% of the respective 3H]inositol-labeled lipids recovered from the nuclear fraction. While both the plasma membrane and nuclear fraction contained polyphosphoinositides, the distribution of the phosphoinositides and the amount of inositol-labeled lipid were distinct. For example, the nuclear fraction had a higher percentage of LPI and PIP2 and less PI and LPIP than the plasma membrane fraction. The amount of 3H]inositol-labeled lipid recovered from the nuclear fraction per mg protein was an order of magnitude lower than that recovered from either the plasma membrane of lower phase fraction isolated by aqueous two-phase partitioning, or from whole cells and protoplasts. In addition, when the ratio of the 3H]inositol-labeled lipid was compared to total 14C]myristate-labeled lipid recovered there was three to ten fold less 3H] relative to 14C] in the nuclear fraction.These data indicate that while the polyphosphoinositides are a relatively high percentage of the inositol lipid in the nuclear fraction, the inositol lipid was only a small portion of the total lipid in the nuclei. Despite this low concentration of inositol lipid, when
32P]-ATP was added to the isolated nuclei,32P-labeled PIP and PIP2 were synthesized. Thus, the carrot nuclei contained PI and PIP kinase as well as the polyphosphoinositides.Abbreviations PI
phosphatidylinositol
- LPI
lysophosphatidylinositol
- PIP
phosphatidylinositol monophosphate
- LPIP
lysophosphatidylinositol monophosphate
- PIP2
phosphatidylinositol bisphosphate
- DAG
diacylglycerol
- IP3
inositol 1,4,5-trisphosphate |
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Keywords: | Phosphatidylinositol Lysophosphatidylinositol Phosphoinositides Nuclei Membrane |
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