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Phosphate deprivation induces transfer of DGDG galactolipid from chloroplast to mitochondria.

Jouhet J, Maréchal E, Baldan B, Bligny R, Joyard J, Block MA - J. Cell Biol. (2004)

Bottom Line: Mitochondria do not synthesize this pool of DGDG, which structure is shown to be characteristic of a DGD type enzyme present in plastid envelope.This transfer does not apparently involve the endomembrane system and would rather be dependent upon contacts between plastids and mitochondria.Contacts sites are favored at early stages of phosphate deprivation when DGDG cell content is just starting to respond to phosphate deprivation.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire de Physiologie Cellulaire Végétale, UMR 5168 (CNRS/CEA/Université Jseph Fourier/INRA), DRDC-PCV, CEA-Grenoble, Grenoble, France.

ABSTRACT
In many soils plants have to grow in a shortage of phosphate, leading to development of phosphate-saving mechanisms. At the cellular level, these mechanisms include conversion of phospholipids into glycolipids, mainly digalactosyldiacylglycerol (DGDG). The lipid changes are not restricted to plastid membranes where DGDG is synthesized and resides under normal conditions. In plant cells deprived of phosphate, mitochondria contain a high concentration of DGDG, whereas mitochondria have no glycolipids in control cells. Mitochondria do not synthesize this pool of DGDG, which structure is shown to be characteristic of a DGD type enzyme present in plastid envelope. The transfer of DGDG between plastid and mitochondria is investigated and detected between mitochondria-closely associated envelope vesicles and mitochondria. This transfer does not apparently involve the endomembrane system and would rather be dependent upon contacts between plastids and mitochondria. Contacts sites are favored at early stages of phosphate deprivation when DGDG cell content is just starting to respond to phosphate deprivation.

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Glycerolipid analysis of total cell and mitochondria fractions from control and 3 d Pi-deprived A. thaliana cells. (A) Glycerolipid composition. SD was calculated on four independent measurements in each case. (B) Fatty acid composition of DGDG isolated either from total cell extracts from 3 d Pi-deprived cells and control cells or from mitochondria fraction from 3 d Pi-deprived cells.
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fig3: Glycerolipid analysis of total cell and mitochondria fractions from control and 3 d Pi-deprived A. thaliana cells. (A) Glycerolipid composition. SD was calculated on four independent measurements in each case. (B) Fatty acid composition of DGDG isolated either from total cell extracts from 3 d Pi-deprived cells and control cells or from mitochondria fraction from 3 d Pi-deprived cells.

Mentions: Lipids were extracted from both types of mitochondria and their composition was compared with that of cells. Fig. 3 A shows results of glycerolipid analyses normalized to the total amount of glycerolipid in each fraction. The composition of cells grown with or without Pi was consistent with data published earlier (Essigmann et al., 1998; Härtel et al., 1998; Jouhet et al., 2003). DPG was found at a relatively high level in both types of cells, indicating that mitochondria lipids represent a fair proportion of total cell lipids. In Pi-deprived cells, we mainly observed a decrease in phospholipids and a high increase in DGDG and sulfoquinovosyldiacylglycerol (SQDG). Lipid composition of mitochondria isolated from control cells was similar to that reported earlier, containing mostly phosphatidylethanolamine (PE) and PC (Douce, 1985; Harwood, 1987). Only traces of MGDG and DGDG were detected. The mol percentage of DPG was three times higher in isolated mitochondria than in whole cells. In mitochondria isolated from Pi-deprived cells, the levels of phospholipids (i.e., PC, PE, and PG) were all lower except for DPG, which was present in higher proportion. Contents in MGDG and SQDG were slightly higher than in mitochondria from control cells, but both remained at a low level. By contrast, the level of DGDG was remarkably higher, representing >18% of the −Pi mitochondria lipids. By analyzing the lipid contamination attributable to chloroplast envelope with mitochondrial lipid data, we calculated that the amount of DGDG issued from envelope contamination is much lower than the amount of DGDG measured in the mitochondria fraction (Table S1), indicating that most of the DGDG detected in mitochondria upon 3 d of Pi deprivation was indeed located in mitochondria.


Phosphate deprivation induces transfer of DGDG galactolipid from chloroplast to mitochondria.

Jouhet J, Maréchal E, Baldan B, Bligny R, Joyard J, Block MA - J. Cell Biol. (2004)

Glycerolipid analysis of total cell and mitochondria fractions from control and 3 d Pi-deprived A. thaliana cells. (A) Glycerolipid composition. SD was calculated on four independent measurements in each case. (B) Fatty acid composition of DGDG isolated either from total cell extracts from 3 d Pi-deprived cells and control cells or from mitochondria fraction from 3 d Pi-deprived cells.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172463&req=5

fig3: Glycerolipid analysis of total cell and mitochondria fractions from control and 3 d Pi-deprived A. thaliana cells. (A) Glycerolipid composition. SD was calculated on four independent measurements in each case. (B) Fatty acid composition of DGDG isolated either from total cell extracts from 3 d Pi-deprived cells and control cells or from mitochondria fraction from 3 d Pi-deprived cells.
Mentions: Lipids were extracted from both types of mitochondria and their composition was compared with that of cells. Fig. 3 A shows results of glycerolipid analyses normalized to the total amount of glycerolipid in each fraction. The composition of cells grown with or without Pi was consistent with data published earlier (Essigmann et al., 1998; Härtel et al., 1998; Jouhet et al., 2003). DPG was found at a relatively high level in both types of cells, indicating that mitochondria lipids represent a fair proportion of total cell lipids. In Pi-deprived cells, we mainly observed a decrease in phospholipids and a high increase in DGDG and sulfoquinovosyldiacylglycerol (SQDG). Lipid composition of mitochondria isolated from control cells was similar to that reported earlier, containing mostly phosphatidylethanolamine (PE) and PC (Douce, 1985; Harwood, 1987). Only traces of MGDG and DGDG were detected. The mol percentage of DPG was three times higher in isolated mitochondria than in whole cells. In mitochondria isolated from Pi-deprived cells, the levels of phospholipids (i.e., PC, PE, and PG) were all lower except for DPG, which was present in higher proportion. Contents in MGDG and SQDG were slightly higher than in mitochondria from control cells, but both remained at a low level. By contrast, the level of DGDG was remarkably higher, representing >18% of the −Pi mitochondria lipids. By analyzing the lipid contamination attributable to chloroplast envelope with mitochondrial lipid data, we calculated that the amount of DGDG issued from envelope contamination is much lower than the amount of DGDG measured in the mitochondria fraction (Table S1), indicating that most of the DGDG detected in mitochondria upon 3 d of Pi deprivation was indeed located in mitochondria.

Bottom Line: Mitochondria do not synthesize this pool of DGDG, which structure is shown to be characteristic of a DGD type enzyme present in plastid envelope.This transfer does not apparently involve the endomembrane system and would rather be dependent upon contacts between plastids and mitochondria.Contacts sites are favored at early stages of phosphate deprivation when DGDG cell content is just starting to respond to phosphate deprivation.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire de Physiologie Cellulaire Végétale, UMR 5168 (CNRS/CEA/Université Jseph Fourier/INRA), DRDC-PCV, CEA-Grenoble, Grenoble, France.

ABSTRACT
In many soils plants have to grow in a shortage of phosphate, leading to development of phosphate-saving mechanisms. At the cellular level, these mechanisms include conversion of phospholipids into glycolipids, mainly digalactosyldiacylglycerol (DGDG). The lipid changes are not restricted to plastid membranes where DGDG is synthesized and resides under normal conditions. In plant cells deprived of phosphate, mitochondria contain a high concentration of DGDG, whereas mitochondria have no glycolipids in control cells. Mitochondria do not synthesize this pool of DGDG, which structure is shown to be characteristic of a DGD type enzyme present in plastid envelope. The transfer of DGDG between plastid and mitochondria is investigated and detected between mitochondria-closely associated envelope vesicles and mitochondria. This transfer does not apparently involve the endomembrane system and would rather be dependent upon contacts between plastids and mitochondria. Contacts sites are favored at early stages of phosphate deprivation when DGDG cell content is just starting to respond to phosphate deprivation.

Show MeSH
Related in: MedlinePlus