Assessment of mitochondria as a compartment for phosphatidylinositol synthesis in Solanum tuberosum.
The outer mitochondrial membrane is particularly rich in phosphatidylinositol (PtdIns), a phospholipid found in different amounts in all eukaryotic membranes, but not synthesized in situ by all. PtdIns is therefore subjected to traffic from the synthesizing membranes to the non-synthesizing ones. The contribution of mitochondria to the cell PtdIns pool has never been the focus of a specific study in plants, whereas in yeast, the presence of the enzyme responsible for synthesis, PtdIns synthase (PIS, cytidine 5'-diphospho-1,2-diacyl-sn-glycerol:myo-inositol 3-phosphatidyltransferase, EC 2.7.8.11), has clearly been demonstrated in mitochondria. As these organelles have now been shown to be responsible for the synthesis of several lipids, the present work aimed at evaluating mitochondria as a compartment for the synthesis of PtdIns in plants. The sub-cellular localization of PIS was studied in Solanum tuberosum L. by membrane fractionation, enzymatic analysis and by confocal microscopy in living cells. In potato, beside the endoplasmic reticulum, the activity of PIS was found to be tightly associated to mitochondria. Using a fluorescent reporter fusion, the enzyme was also found to be associated to these organelles. The enzyme was not present at the plasma membrane. A comparison of the localization in other cell systems suggests that the mitochondrial localization could be regulated.
UPMC Univ Paris 06, UR5, Physiologie Cellulaire et Moléculaire des Plantes, F-75252 Paris Cedex 05, France.
Jacques
J
Davy de Virville
Spencer
S
Brown
Françoise
F
Cochet
Marie-Noëlle
MN
Soler
Michèle
M
Hoffelt
Eric
E
Ruelland
Alain
A
Zachowski
Sylvie
S
Collin
D051607:CDP-Diacylglycerol-Inositol 3-Phosphatidyltransferase / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D008928:Mitochondria / Q000201:enzymology / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism; D010716:Phosphatidylinositols / Q000096:biosynthesis*; D011198:Solanum tuberosum / Q000378:metabolism*
D010716:Phosphatidylinositols; D051607:CDP-Diacylglycerol-Inositol 3-Phosphatidyltransferase