Subcellular localization and dynamics of a digalactolipid-like epitope in Toxoplasma gondii

Abstract

Toxoplasma gondii is a unicellular parasite characterized by unique extracellular and intracellular membrane compartments. The lipid composition of subcellular membranes has not been determined, limiting our understanding of lipid homeostasis, control, and trafficking, a series of processes involved in pathogenesis. In addition to a mitochondrion, Toxoplasma contains a plastid called the apicoplast. The occurrence of a plastid raised the question of the presence of chloroplast galactolipids. Using three independent rabbit and rat antibodies against digalactosyldiacylglycerol (DGDG) from plant chloroplasts, we detected a class of Toxoplasma lipids harboring a digalactolipid-like epitope (DGLE). Immunolabeling characterization supports the notion that the DGLE polar head is similar to that of DGDG. Mass spectrometry analyses indicated that dihexosyl lipids having various hydrophobic moieties (ceramide, diacylglycerol, and acylalkylglycerol) might react with anti-DGDG, but we cannot exclude the possibility that more complex dihexosyl-terminated lipids might also be immunolabeled. DGLE localization was analyzed by immunofluorescence and immunoelectron microscopy and confirmed by subcellular fractionation. No immunolabeling of the apicoplast could be observed. DGLE was scattered in pellicle membrane domains in extracellular tachyzoites and was relocalized to the anterior tip of the cell upon invasion in an actin-dependent manner, providing insights on a possible role in pathogenetic processes. DGLE was detected in other Apicomplexa (i.e

The Cryptic Plastid of Euglena longa Defines a New Type of Nonphotosynthetic Plastid Organelle

“…These have previously been documented in several nonphotosynthetic algae, e.g., colorless diatoms (85,86). On the other hand, the apicoplast (87,88), and most likely also the relic plastid of Helicosporidium (based on our analysis of the respective genome data in reference 17), lacks galactolipid and SQDG synthesis completely. The reason for the differential retention of these lipids in different colorless plastids remains to be investigated further.…”

The Cryptic Plastid of Euglena longa Defines a New Type of Nonphotosynthetic Plastid Organelle

“…These have previously been documented in several nonphotosynthetic algae, e.g., colorless diatoms (85,86). On the other hand, the apicoplast (87,88), and most likely also the relic plastid of Helicosporidium (based on our analysis of the respective genome data in reference 17), lacks galactolipid and SQDG synthesis completely. The reason for the differential retention of these lipids in different colorless plastids remains to be investigated further.…”

Identification of Plant-like Galactolipids in Chromera velia, a Photosynthetic Relative of Malaria Parasites

“…In plant chloroplasts, MGDG and DGDG typically represent 75% of the total lipids (1), and high levels of galactolipids in C. velia , a photosynthetic alveolate, are consistent with the importance of these lipids for photosynthesis. By contrast, previous lipidomic analysis of the Apicomplexan parasite T. gondii concluded that hexosyl lipids were only a minor lipid class (20, 21). Because most Apicomplexa are obligate intracellular parasites and depend on their host to provide most nutrients and precursors for membrane biogenesis, the apparent difference (on the basis of HPTLC) in relative abundance of galactolipids between C. velia and T. gondii likely reflects life style difference.…”

“…In contrast, preliminary analyses of the T. gondii DGDG-like lipid indicated localization to the pellicle membranes (20). To assess the subcellular localization of C. velia galactolipids, anti-DGDG serum was used to detect this glycolipid on whole cells (18, 20, 23). Cells were fixed and permeabilized prior to their incubation with the anti-DGDG serum, and fluorescence was detected by confocal microscopy (Fig.…”

The cryptic plastid of Euglena longa defines a new type of non-photosynthetic plastid organelles

“…The photosynthesis-independent role of galactolipids is indicated not only by their presence in the E. longa plastid documented here, but also by previous reports from other non-photosynthetic algae, including the diatom Nitzschia alba (Anderson et al 1978) and the chlorophyte Prototheca wickerhamii (Borza et al 2005), and from non-photosynthetic tissues of plants (Awai et al 2001; Kobayashi 2016). On the other hand, the apicoplast (Botté et al 2008; Botté et al 2013) and most likely also the relic plastid of Helicosporidium (based on our analysis of the respective genome sequence data generated by Pombert et al 2014) lack galactolipid synthesis completely. The reason for the differential retention of galactolipids in different colourless plastids remains unclear.…”

The Cryptic Plastid of Euglena longa Defines a New Type of Nonphotosynthetic Plastid Organelle

“…These have previously been documented in several nonphotosynthetic algae, e.g., colorless diatoms (85,86). On the other hand, the apicoplast (87,88), and most likely also the relic plastid of Helicosporidium (based on our analysis of the respective genome data in reference 17), lacks galactolipid and SQDG synthesis completely. The reason for the differential retention of these lipids in different colorless plastids remains to be investigated further.…”

Identification of Plant-like Galactolipids in Chromera velia, a Photosynthetic Relative of Malaria Parasites

“…In plant chloroplasts, MGDG and DGDG typically represent 75% of the total lipids (1), and high levels of galactolipids in C. velia , a photosynthetic alveolate, are consistent with the importance of these lipids for photosynthesis. By contrast, previous lipidomic analysis of the Apicomplexan parasite T. gondii concluded that hexosyl lipids were only a minor lipid class (20, 21). Because most Apicomplexa are obligate intracellular parasites and depend on their host to provide most nutrients and precursors for membrane biogenesis, the apparent difference (on the basis of HPTLC) in relative abundance of galactolipids between C. velia and T. gondii likely reflects life style difference.…”

“…In contrast, preliminary analyses of the T. gondii DGDG-like lipid indicated localization to the pellicle membranes (20). To assess the subcellular localization of C. velia galactolipids, anti-DGDG serum was used to detect this glycolipid on whole cells (18, 20, 23). Cells were fixed and permeabilized prior to their incubation with the anti-DGDG serum, and fluorescence was detected by confocal microscopy (Fig.…”

The cryptic plastid of Euglena longa defines a new type of non-photosynthetic plastid organelles

“…The photosynthesis-independent role of galactolipids is indicated not only by their presence in the E. longa plastid documented here, but also by previous reports from other non-photosynthetic algae, including the diatom Nitzschia alba (Anderson et al 1978) and the chlorophyte Prototheca wickerhamii (Borza et al 2005), and from non-photosynthetic tissues of plants (Awai et al 2001; Kobayashi 2016). On the other hand, the apicoplast (Botté et al 2008; Botté et al 2013) and most likely also the relic plastid of Helicosporidium (based on our analysis of the respective genome sequence data generated by Pombert et al 2014) lack galactolipid synthesis completely. The reason for the differential retention of galactolipids in different colourless plastids remains unclear.…”

The Cryptic Plastid of Euglena longa Defines a New Type of Nonphotosynthetic Plastid Organelle

“…These have previously been documented in several nonphotosynthetic algae, e.g., colorless diatoms (85,86). On the other hand, the apicoplast (87,88), and most likely also the relic plastid of Helicosporidium (based on our analysis of the respective genome data in reference 17), lacks galactolipid and SQDG synthesis completely. The reason for the differential retention of these lipids in different colorless plastids remains to be investigated further.…”

Identification of Plant-like Galactolipids in Chromera velia, a Photosynthetic Relative of Malaria Parasites

“…In plant chloroplasts, MGDG and DGDG typically represent 75% of the total lipids (1), and high levels of galactolipids in C. velia , a photosynthetic alveolate, are consistent with the importance of these lipids for photosynthesis. By contrast, previous lipidomic analysis of the Apicomplexan parasite T. gondii concluded that hexosyl lipids were only a minor lipid class (20, 21). Because most Apicomplexa are obligate intracellular parasites and depend on their host to provide most nutrients and precursors for membrane biogenesis, the apparent difference (on the basis of HPTLC) in relative abundance of galactolipids between C. velia and T. gondii likely reflects life style difference.…”

“…In contrast, preliminary analyses of the T. gondii DGDG-like lipid indicated localization to the pellicle membranes (20). To assess the subcellular localization of C. velia galactolipids, anti-DGDG serum was used to detect this glycolipid on whole cells (18, 20, 23). Cells were fixed and permeabilized prior to their incubation with the anti-DGDG serum, and fluorescence was detected by confocal microscopy (Fig.…”

The cryptic plastid of Euglena longa defines a new type of non-photosynthetic plastid organelles

“…The photosynthesis-independent role of galactolipids is indicated not only by their presence in the E. longa plastid documented here, but also by previous reports from other non-photosynthetic algae, including the diatom Nitzschia alba (Anderson et al 1978) and the chlorophyte Prototheca wickerhamii (Borza et al 2005), and from non-photosynthetic tissues of plants (Awai et al 2001; Kobayashi 2016). On the other hand, the apicoplast (Botté et al 2008; Botté et al 2013) and most likely also the relic plastid of Helicosporidium (based on our analysis of the respective genome sequence data generated by Pombert et al 2014) lack galactolipid synthesis completely. The reason for the differential retention of galactolipids in different colourless plastids remains unclear.…”