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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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Localization of DGDG in mitochondria of A. thaliana cells deprived of Pi for 3 d. Cells (A, control; B–D, Pi-deprived) were processed for indirect immunofluorescence labeling using anti-DGDG with secondary antibodies coupled to BODIPY and either anti-BCCP1, for chloroplast detection (A and B), or anti-HPPK (C), for mitochondria detection, with secondary antibodies coupled to Alexa 594. In D, mitochondria were visualized by staining with Mitotracker orange CMTMRos. Cells were observed by confocal microscopy. Bars: A–C, 8 μm; D, 20 μm.
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fig1: Localization of DGDG in mitochondria of A. thaliana cells deprived of Pi for 3 d. Cells (A, control; B–D, Pi-deprived) were processed for indirect immunofluorescence labeling using anti-DGDG with secondary antibodies coupled to BODIPY and either anti-BCCP1, for chloroplast detection (A and B), or anti-HPPK (C), for mitochondria detection, with secondary antibodies coupled to Alexa 594. In D, mitochondria were visualized by staining with Mitotracker orange CMTMRos. Cells were observed by confocal microscopy. Bars: A–C, 8 μm; D, 20 μm.

Mentions: 3 d after the beginning of Pi deprivation, A. thaliana cells grown as a suspension in liquid medium don't divide anymore. Their lipid composition has been modified compared with control cells. Particularly, the level of DGDG has increased from less than 10% up to 30–35% of total glycerolipids during the first day of deprivation, and this level is now stable (Jouhet et al., 2003). To understand where DGDG is localized at this stage, routinely grown Arabidopsis cell cultures were transferred for 3 d in a medium devoid of Pi (−Pi medium) or containing 1 mM Pi (control). Subcellular localization of DGDG was then assayed using antibodies raised against this lipid. Specificity of anti-DGDG antibodies for DGDG was assessed based on absence of reaction with other lipids or proteins of the cell (Maréchal et al., 2002). Fig. 1 A and Fig. S1 (available at http://www.jcb.org/cgi/content/full/jcb.200407022/DC1) show that in control cells, DGDG was only detected in plastids because DGDG-coupled epifluorescence was associated with epifluorescence coupled with the biotin carboxyl carrier protein (BCCP) subunit of acetyl-CoA synthetase, a protein present in the plastid stroma (Alban et al., 1994). In Pi-deprived cells, the situation appears to be more complex because DGDG-associated fluorescence was no more restricted to plastids and was also visible in many small spots distinct from plastids (Fig. 1 B). Some of these spots were present at the periphery of the cell, likely associated with plasma membrane as reported by Andersson et al. (2003). In addition, by comparison with the epifluorescence coupled with dihydropterin pyrophosphokinase (HPPK), a protein from mitochondria (Mouillon et al., 2002), we observed that DGDG-coupled fluorescence was also associated with that of mitochondrial markers (Fig. 1 C). Co-labeling with DGDG antibodies and MitoTracker orange CMTMRos (Molecular Probes, Inc.) confirmed this observation (Fig. 1 D). Therefore, these data indicate that in cells deprived of Pi, DGDG is present outside of plastids, and notably 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)

Localization of DGDG in mitochondria of A. thaliana cells deprived of Pi for 3 d. Cells (A, control; B–D, Pi-deprived) were processed for indirect immunofluorescence labeling using anti-DGDG with secondary antibodies coupled to BODIPY and either anti-BCCP1, for chloroplast detection (A and B), or anti-HPPK (C), for mitochondria detection, with secondary antibodies coupled to Alexa 594. In D, mitochondria were visualized by staining with Mitotracker orange CMTMRos. Cells were observed by confocal microscopy. Bars: A–C, 8 μm; D, 20 μm.
© Copyright Policy
Related In: Results  -  Collection

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

fig1: Localization of DGDG in mitochondria of A. thaliana cells deprived of Pi for 3 d. Cells (A, control; B–D, Pi-deprived) were processed for indirect immunofluorescence labeling using anti-DGDG with secondary antibodies coupled to BODIPY and either anti-BCCP1, for chloroplast detection (A and B), or anti-HPPK (C), for mitochondria detection, with secondary antibodies coupled to Alexa 594. In D, mitochondria were visualized by staining with Mitotracker orange CMTMRos. Cells were observed by confocal microscopy. Bars: A–C, 8 μm; D, 20 μm.
Mentions: 3 d after the beginning of Pi deprivation, A. thaliana cells grown as a suspension in liquid medium don't divide anymore. Their lipid composition has been modified compared with control cells. Particularly, the level of DGDG has increased from less than 10% up to 30–35% of total glycerolipids during the first day of deprivation, and this level is now stable (Jouhet et al., 2003). To understand where DGDG is localized at this stage, routinely grown Arabidopsis cell cultures were transferred for 3 d in a medium devoid of Pi (−Pi medium) or containing 1 mM Pi (control). Subcellular localization of DGDG was then assayed using antibodies raised against this lipid. Specificity of anti-DGDG antibodies for DGDG was assessed based on absence of reaction with other lipids or proteins of the cell (Maréchal et al., 2002). Fig. 1 A and Fig. S1 (available at http://www.jcb.org/cgi/content/full/jcb.200407022/DC1) show that in control cells, DGDG was only detected in plastids because DGDG-coupled epifluorescence was associated with epifluorescence coupled with the biotin carboxyl carrier protein (BCCP) subunit of acetyl-CoA synthetase, a protein present in the plastid stroma (Alban et al., 1994). In Pi-deprived cells, the situation appears to be more complex because DGDG-associated fluorescence was no more restricted to plastids and was also visible in many small spots distinct from plastids (Fig. 1 B). Some of these spots were present at the periphery of the cell, likely associated with plasma membrane as reported by Andersson et al. (2003). In addition, by comparison with the epifluorescence coupled with dihydropterin pyrophosphokinase (HPPK), a protein from mitochondria (Mouillon et al., 2002), we observed that DGDG-coupled fluorescence was also associated with that of mitochondrial markers (Fig. 1 C). Co-labeling with DGDG antibodies and MitoTracker orange CMTMRos (Molecular Probes, Inc.) confirmed this observation (Fig. 1 D). Therefore, these data indicate that in cells deprived of Pi, DGDG is present outside of plastids, and notably 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