The Experts below are selected from a list of 1020 Experts worldwide ranked by ideXlab platform
Peter Dormann - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and transfer of Galactolipids in the chloroplast envelope membranes of Arabidopsis thaliana.
Proceedings of the National Academy of Sciences of the United States of America, 2016Co-Authors: Amélie A. Kelly, Barbara Kalisch, Georg Hölzl, Christoph Benning, Sandra Schulze, Juliane Thiele, Michael Melzer, Rebecca L. Roston, Peter DormannAbstract:Galactolipids [monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG)] are the hallmark lipids of photosynthetic membranes. The Galactolipid synthases MGD1 and DGD1 catalyze consecutive galactosyltransfer reactions but localize to the inner and outer chloroplast envelopes, respectively, necessitating intermembrane lipid transfer. Here we show that the N-terminal sequence of DGD1 (NDGD1) is required for Galactolipid transfer between the envelopes. Different diglycosyllipid synthases (DGD1, DGD2, and Chloroflexus glucosyltransferase) were introduced into the dgd1-1 mutant of Arabidopsis in fusion with N-terminal extensions (NDGD1 and NDGD2) targeting to the outer envelope. Reconstruction of DGDG synthesis in the outer envelope membrane was observed only with diglycosyllipid synthase fusion proteins carrying NDGD1, indicating that NDGD1 enables Galactolipid translocation between envelopes. NDGD1 binds to phosphatidic acid (PA) in membranes and mediates PA-dependent membrane fusion in vitro. These findings provide a mechanism for the sorting and selective channeling of lipid precursors between the Galactolipid pools of the two envelope membranes.
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Nitrogen deficiency in Arabidopsis affects Galactolipid composition and gene expression and results in accumulation of fatty acid phytyl esters
The Plant Journal, 2007Co-Authors: Nicole Gaude, Felix Kessler, Claire Bréhélin, Gilbert Tischendorf, Peter DormannAbstract:Nitrogen is an essential nutrient for plants because it represents a major constituent of numerous cellular compounds, including proteins, amino acids, nucleic acids and lipids. While N deprivation is known to have severe consequences for primary carbon metabolism, the effect on chloroplast lipid metabolism has not been analysed in higher plants. Nitrogen limitation in Arabidopsis led to a decrease in the chloroplast Galactolipid monogalactosyldiacylglycerol (MGDG) and a concomitant increase in digalactosyldiacylglycerol (DGDG), which correlated with an elevated expression of the DGDG synthase genes DGD1 and DGD2. The amounts of triacylglycerol and free fatty acids increased during N deprivation. Furthermore, phytyl esters accumulated containing medium-chain fatty acids (12:0, 14:0) and a large amount of hexadecatrienoic acid (16:3). Fatty acid phytyl esters were localized to chloroplasts, in particular to thylakoids and plastoglobules. Different polyunsaturated acyl groups were found in phytyl esters accumulating in Arabidopsis lipid mutants and in other plants, including 16:3 and 18:3 species. Therefore N deficiency in higher plants results in a coordinated breakdown of Galactolipids and chlorophyll with deposition of specific fatty acid phytyl esters in thylakoids and plastoglobules of chloroplasts.
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Green light for Galactolipid trafficking
Current opinion in plant biology, 2004Co-Authors: Amélie A. Kelly, Peter DormannAbstract:Galactolipids not only play a crucial role in photosynthesis but are also important for the adaptation of membrane-lipid composition in plants to phosphate-limiting conditions. The enzymes of Galactolipid assembly have been localised to the envelope membranes of chloroplasts. Lipid trafficking is essential for Galactolipid synthesis and redistribution because lipid precursors originate from two compartments, the endoplasmic reticulum (ER) and the plastid, and because Galactolipids have to be transported to extraplastidial membranes during phosphate deprivation. Analysis of Arabidopsis mutants that are impaired in Galactolipid synthesis (i.e. dgd1 and dgd2) or in ER-to-plastid lipid transport (i.e. tgd1) has resulted in the identification of a processive galactosyltransferase whose function is still enigmatic.
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Galactolipids rule in seed plants
Trends in plant science, 2002Co-Authors: Peter Dormann, Christoph BenningAbstract:Chloroplast membranes contain high levels of the Galactolipids monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG). The isolation of the genes involved in the biosynthesis of MGDG and DGDG, and the identification of Galactolipid-deficient Arabidopsis mutants has greatly facilitated the analysis of Galactolipid biosynthesis and function. Galactolipids are found in X-ray structures of photosynthetic complexes, suggesting a direct role in photosynthesis. Furthermore, Galactolipids can substitute for phospholipids, as suggested by increases in the Galactolipid:phospholipid ratio after phosphate deprivation. The ratio of MGDG to DGDG is also crucial for the physical phase of thylakoid membranes and might be regulated.
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DGD1-independent biosynthesis of extraplastidic Galactolipids after phosphate deprivation in Arabidopsis
Proceedings of the National Academy of Sciences of the United States of America, 2000Co-Authors: Heiko Härtel, Peter DormannAbstract:The Galactolipids, mono- and digalactosyldiacylglycerol (DGDG), are the most common nonphosphorous lipids in the biosphere and account for 80% of the membrane lipids found in green plant tissues. These lipids are major constituents of photosynthetic membranes (thylakoids), and a large body of evidence suggests that Galactolipids are associated primarily with plastid membranes in seed plants. A null-mutant of Arabidopsis (dgd1), which lacks the DGDG synthase (DGD1) resulting in a 90% reduction in the amount of DGDG under normal growth conditions, accumulated DGDG after phosphate deprivation up to 60% of the amount present in the wild type. This observation suggests the existence of a DGD1-independent pathway of Galactolipid biosynthesis. The fatty acid composition of the newly formed DGDG was distinct, showing an enrichment of 16-carbon fatty acids in the C-1 position of the glycerol backbone of DGDG. Roots with their rudimentary plastids accumulated large amounts of DGDG after phosphate deprivation, suggesting that this Galactolipid may be located in extraplastidic membranes. Corroborating evidence for this hypothesis was obtained directly by fractionation of subcellular membranes from leaf tissue and indirectly by lipid analysis of the phosphate-deprived fad3 mutant primarily deficient in extraplastidic fatty acid desaturation. The discovery of extraplastidic DGDG biosynthesis induced by phosphate deprivation has revealed a biochemical mechanism for plants to conserve phosphate. Apparently, plants replace phospholipids with nonphosphorous Galactolipids if environmental conditions such as phosphate deprivation require this for survival.
Hiroyuki Ohta - One of the best experts on this subject based on the ideXlab platform.
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an engineered lipid remodeling system using a Galactolipid synthase promoter during phosphate starvation enhances oil accumulation in plants
Frontiers in Plant Science, 2015Co-Authors: Mie Shimojima, Yuka Madoka, Ryota Fujiwara, Masato Murakawa, Yushi Yoshitake, Keiko Ikeda, Ryota Koizumi, Keiji Endo, Katsuya Ozaki, Hiroyuki OhtaAbstract:Inorganic phosphate (Pi) depletion is a serious problem for plant growth. Membrane lipid remodeling is a defense mechanism that plants use to survive Pi-depleted conditions. During Pi starvation, phospholipids are degraded to supply Pi for other essential biological processes, whereas Galactolipid synthesis in plastids is up-regulated via the transcriptional activation of monogalactosyldiacylglycerol synthase 3 (MGD3). Thus, the produced Galactolipids are transferred to extraplastidial membranes to substitute for phospholipids. We found that, Pi starvation induced oil accumulation in the vegetative tissues of various seed plants without activating the transcription of enzymes involved in the later steps of triacylglycerol (TAG) biosynthesis. Moreover, the Arabidopsis starchless phosphoglucomutase mutant, pgm-1, accumulated higher TAG levels than did wild-type plants under Pi-depleted conditions. We generated transgenic plants that expressed a key gene involved in TAG synthesis using the Pi deficiency-responsive MGD3 promoter in wild-type and pgm-1 backgrounds. During Pi starvation, the transgenic plants accumulated higher TAG amounts compared with the non-transgenic plants, suggesting that the Pi deficiency-responsive promoter of Galactolipid synthase in plastids may be useful for producing transgenic plants that accumulate more oil under Pi-depleted conditions.
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phylogeny of Galactolipid synthase homologs together with their enzymatic analyses revealed a possible origin and divergence time for photosynthetic membrane biogenesis
DNA Research, 2012Co-Authors: Yuichi Yuzawa, Mie Shimojima, Hidenori Nishihara, Tsuyoshi Haraguchi, Shinji Masuda, Atsushi Shimoyama, Hideya Yuasa, Norihiro Okada, Hiroyuki OhtaAbstract:The photosynthetic membranes of cyanobacteria and chloroplasts of higher plants have remarkably similar lipid compositions. In particular, thylakoid membranes of both cyanobacteria and chloroplasts are composed of Galactolipids, of which monogalactosyldiacylglycerol (MGDG) is the most abundant, although MGDG biosynthetic pathways are different in these organisms. Comprehensive phylogenetic analysis revealed that MGDG synthase (MGD) homologs of filamentous anoxygenic phototrophs Chloroflexi have a close relationship with MGDs of Viridiplantae (green algae and land plants). Furthermore, analyses for the sugar specificity and anomeric configuration of the sugar head groups revealed that one of the MGD homologs exhibited a true MGDG synthetic activity. We therefore presumed that higher plant MGDs are derived from this ancestral type of MGD genes, and genes involved in membrane biogenesis and photosystems have been already functionally associated at least at the time of Chloroflexi divergence. As MGD gene duplication is an important event during plastid evolution, we also estimated the divergence time of type A and B MGDs. Our analysis indicated that these genes diverged ∼323 million years ago, when Spermatophyta (seed plants) were appearing. Galactolipid synthesis is required to produce photosynthetic membranes; based on MGD gene sequences and activities, we have proposed a novel evolutionary model that has increased our understanding of photosynthesis evolution.
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critical regulation of Galactolipid synthesis controls membrane differentiation and remodeling in distinct plant organs and following environmental changes
Progress in Lipid Research, 2011Co-Authors: Mie Shimojima, Hiroyuki OhtaAbstract:The plant Galactolipids, monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), are the most abundant lipids in chloroplast membranes, and they constitute the majority of total membrane lipids in plants. MGDG is synthesized by two types of MGDG synthase, type-A (MGD1) and type-B (MGD2, MGD3). These MGDG synthases have distinct roles in Arabidopsis. In photosynthetic organs, Type A MGD is responsible for the bulk of MGDG synthesis, whereas Type B MGD is expressed in non-photosynthetic organs such as roots and flowers and mainly contributes to DGDG accumulation under phosphate deficiency. Similar to MGDG synthesis, DGDG is synthesized by two synthases, DGD1 and DGD2; DGD1 is responsible for the majority of DGDG synthesis, whereas DGD2 makes its main contribution under phosphate deficiency. These Galactolipid synthases are regulated by light, plant hormones, redox state, phosphatidic acid levels, and various stress conditions such as drought and nutrient limitation. Maintaining the appropriate ratio of these two Galactolipids in chloroplasts is important for stabilizing thylakoid membranes and maximizing the efficiency of photosynthesis. Here we review progress made in the last decade towards a better understanding of the pathways regulating plant Galactolipid biosynthesis.
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Phylogeny of Galactolipid Synthase Homologs Together with their Enzymatic Analyses Revealed a Possible Origin and Divergence Time for Photosynthetic Membrane Biogenesis
2011Co-Authors: Yuichi Yuzawa, Mie Shimojima, Hidenori Nishihara, Tsuyoshi Haraguchi, Shinji Masuda, Atsushi Shimoyama, Hideya Yuasa, Norihiro Okada, Hiroyuki OhtaAbstract:The photosynthetic membranes of cyanobacteria and chloroplasts of higher plants have remarkably similar lipid compositions. In particular, thylakoid membranes of both cyanobacteria and chloroplasts are composed of Galactolipids, of which monogalactosyldiacylglycerol (MGDG) is the most abundant, al-though MGDG biosynthetic pathways are different in these organisms. Comprehensive phylogenetic ana-lysis revealed that MGDG synthase (MGD) homologs of filamentous anoxygenic phototrophs Chloroflexi have a close relationship with MGDs of Viridiplantae (green algae and land plants). Furthermore, analyses for the sugar specificity and anomeric configuration of the sugar head groups revealed that one of the MGD homologs exhibited a true MGDG synthetic activity. We therefore presumed that higher plant MGDs are derived from this ancestral type of MGD genes, and genes involved in membrane biogenesis and photosystems have been already functionally associated at least at the time of Chloroflexi divergence. As MGD gene duplication is an important event during plastid evolution, we also estimated the divergence time of type A and B MGDs. Our analysis indicated that these genes diverged ∼323 million years ago, when Spermatophyta (seed plants) were appearing. Galactolipid synthesis is required to produce photo-synthetic membranes; based on MGD gene sequences and activities, we have proposed a novel evolution
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arabidopsis lipins mediate eukaryotic pathway of lipid metabolism and cope critically with phosphate starvation
Proceedings of the National Academy of Sciences of the United States of America, 2009Co-Authors: Yuki Nakamura, Mie Shimojima, Ryota Koizumi, Guanghou Shui, Markus R Wenk, Toshiro Ito, Hiroyuki OhtaAbstract:Phosphate is an essential nutrient for plant viability. It is well-established that phosphate starvation triggers membrane lipid remodeling, a process that converts significant portion of phospholipids to non-phosphorus-containing Galactolipids. This remodeling is mediated by either phospholipase C (PLC) or phospholipase D (PLD) in combination with phosphatidate phosphatase (PAP). Two PLC genes, NPC4 and NPC5, and PLD genes, PLDζ1 and PLDζ2, are shown to be involved in the remodeling. However, gene knockout studies show that none of them plays decisive roles in the remodeling. Thus, although this phenomenon is widely observed among plants, the key enzyme(s) responsible for the lipid remodeling in a whole plant body is unknown; therefore, the physiological significance of this conversion process has remained to be elucidated. We herein focused on PAP as a key enzyme for this adaptation, and identified Arabidopsis lipin homologs, AtPAH1 and AtPAH2, that encode the PAPs involved in Galactolipid biosynthesis. Double mutant pah1pah2 plants had decreased phosphatidic acid hydrolysis, thus affecting the eukaryotic pathway of Galactolipid synthesis. Upon phosphate starvation, pah1pah2 plants were severely impaired in growth and membrane lipid remodeling. These results indicate that PAH1 and PAH2 are the PAP responsible for the eukaryotic pathway of Galactolipid synthesis, and the membrane lipid remodeling mediated by these two enzymes is an essential adaptation mechanism to cope with phosphate starvation.
Didier Marion - One of the best experts on this subject based on the ideXlab platform.
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The Spatiotemporal Deposition of Lysophosphatidylcholine Within Starch Granules of Maize Endosperm and its Relationships to the Expression of Genes Involved in Endoplasmic Reticulum-Amyloplast Lipid Trafficking and Galactolipid Synthesis
Plant and Cell Physiology, 2019Co-Authors: Mathieu Gayral, Mathieu Fanuel, Hélène Rogniaux, Michèle Dalgalarrondo, Khalil Elmorjani, Benedicte Bakan, Didier MarionAbstract:The presence of lipids within starch granules is specific to cereal endosperm starches. These starch lipids are composed of lysophospholipids, especially lysophosphatidylcholine (LysoPC) and free fatty acids that strongly impact the assembly and properties of cereal starches. However, the molecular mechanisms associated with this specific lipid routing have never been investigated. In this study, matrix-assisted laser desorption ionization mass spectrometry imaging revealed decreasing gradients in starch LysoPC concentrations from the periphery to the center of developing maize endosperms. This spatiotemporal deposition of starch LysoPC was similar to that previously observed for endoplasmic reticulum (ER)-synthesized storage proteins, i.e. zeins, suggesting that LysoPC might originate in the ER, as already reported for chloroplasts. Furthermore, a decrease of the palmitate concentration of amyloplast Galactolipids was observed during endosperm development, correlated with the preferential trapping of palmitoyl-LysoPC by starch carbohydrates, suggesting a link between LysoPC and Galactolipid synthesis. Using microarray, the homologous genes of the Arabidopsis ER-chloroplast lipid trafficking and Galactolipid synthesis pathways were also expressed in maize endosperm. These strong similarities suggest that the encoded enzymes and transporters are adapted to managing the differences between chloroplast and amyloplast lipid homeostasis. Altogether, our results led us to propose a model where ER-amyloplast lipid trafficking directs the LysoPC towards one of two routes, the first towards the stroma and starch granules and the other towards Galactolipid synthesis.
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Galactosyl headgroup interactions control the molecular packing of wheat lipids in Langmuir films and in hydrated liquid-crystalline mesophases.
Biochimica et Biophysica Acta (BBA) - Biomembranes, 2007Co-Authors: Céline Bottier, Julie Géan, Franck Artzner, Bernard Desbat, Michel Pézolet, Anne Renault, Didier Marion, Véronique ViéAbstract:The behavior of the two major Galactolipids of wheat endosperm, mono- (MGDG) and di-galactosyldiacylglycerol (DGDG) was studied in aqueous dispersion and at the air/liquid interface. The acyl chains of the pure Galactolipids and their binary equimolar mixture are in the fluid or liquid expanded phase. SAXS measurements on liquid-crystalline mesophases associated with the electron density reconstructions show that the DGDG adopts a lamellar phase L(alpha) with parallel orientation of the headgroups with respect to the plane of the bilayer, whereas MGDG forms an inverse hexagonal phase H(II) with a specific organization of galactosyl headgroups. The equimolar mixture shows a different behavior from those previously described with formation of an Im3m cubic phase. In comparing monolayers composed of the pure Galactolipids and their equimolar mixtures, PM-IRRAS spectra show significant differences in the optical properties and orientation of galactosyl groups with respect to the interface. Furthermore, Raman and FTIR spectroscopies show that the acyl chains of the Galactolipid mixture are more ordered compared to those of the pure components. These results suggest strong interactions between MGDG and DGDG galactosyl headgroups and these specific physical properties of Galactolipids are discussed in relation to their biological interest in wheat seed.
Felix Kessler - One of the best experts on this subject based on the ideXlab platform.
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fatty acid phytyl ester synthesis in chloroplasts of arabidopsis
The Plant Cell, 2012Co-Authors: Felix Lippold, Georg Hölzl, Katharina Vom Dorp, Marion Abraham, Vera Wewer, Jenny Lindberg Yilmaz, Ida Lager, Cyrille Montandon, Celine Besagni, Felix KesslerAbstract:During stress or senescence, thylakoid membranes in chloroplasts are disintegrated, and chlorophyll and Galactolipid are broken down, resulting in the accumulation of toxic intermediates, i.e., tetrapyrroles, free phytol, and free fatty acids. Chlorophyll degradation has been studied in detail, but the catabolic pathways for phytol and fatty acids remain unclear. A large proportion of phytol and fatty acids is converted into fatty acid phytyl esters and triacylglycerol during stress or senescence in chloroplasts. We isolated two genes (PHYTYL ESTER SYNTHASE1 [PES1] and PES2) of the esterase/lipase/ thioesterase family of acyltransferases from Arabidopsis thaliana that are involved in fatty acid phytyl ester synthesis in chloroplasts. The two proteins are highly expressed during senescence and nitrogen deprivation. Heterologous expression in yeast revealed that PES1 and PES2 have phytyl ester synthesis and diacylglycerol acyltransferase activities. The enzymes show broad substrate specificities and can employ acyl-CoAs, acyl carrier proteins, and Galactolipids as acyl donors. Double mutant plants (pes1 pes2) grow normally but show reduced phytyl ester and triacylglycerol accumulation. These results demonstrate that PES1 and PES2 are involved in the deposition of free phytol and free fatty acids in the form of phytyl esters in chloroplasts, a process involved in maintaining the integrity of the photosynthetic membrane during abiotic stress and senescence.
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Nitrogen deficiency in Arabidopsis affects Galactolipid composition and gene expression and results in accumulation of fatty acid phytyl esters
The Plant Journal, 2007Co-Authors: Nicole Gaude, Felix Kessler, Claire Bréhélin, Gilbert Tischendorf, Peter DormannAbstract:Nitrogen is an essential nutrient for plants because it represents a major constituent of numerous cellular compounds, including proteins, amino acids, nucleic acids and lipids. While N deprivation is known to have severe consequences for primary carbon metabolism, the effect on chloroplast lipid metabolism has not been analysed in higher plants. Nitrogen limitation in Arabidopsis led to a decrease in the chloroplast Galactolipid monogalactosyldiacylglycerol (MGDG) and a concomitant increase in digalactosyldiacylglycerol (DGDG), which correlated with an elevated expression of the DGDG synthase genes DGD1 and DGD2. The amounts of triacylglycerol and free fatty acids increased during N deprivation. Furthermore, phytyl esters accumulated containing medium-chain fatty acids (12:0, 14:0) and a large amount of hexadecatrienoic acid (16:3). Fatty acid phytyl esters were localized to chloroplasts, in particular to thylakoids and plastoglobules. Different polyunsaturated acyl groups were found in phytyl esters accumulating in Arabidopsis lipid mutants and in other plants, including 16:3 and 18:3 species. Therefore N deficiency in higher plants results in a coordinated breakdown of Galactolipids and chlorophyll with deposition of specific fatty acid phytyl esters in thylakoids and plastoglobules of chloroplasts.
Mie Shimojima - One of the best experts on this subject based on the ideXlab platform.
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complete replacement of the Galactolipid biosynthesis pathway with a plant type pathway in the cyanobacterium synechococcus elongatus pcc 7942
Plant and Cell Physiology, 2020Co-Authors: Egi Tritya Apdila, Mie Shimojima, Shukumi Inoue, Koichiro AwaiAbstract:Monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) are the major components of thylakoid membranes and well-conserved from cyanobacteria to chloroplasts. However, cyanobacteria and chloroplasts synthesize these Galactolipids using different pathways and enzymes, but they are believed to share a common ancestor. This fact implies that there was a replacement of the cyanobacterial Galactolipid biosynthesis pathway during the evolution of a chloroplast. In this study, we first replaced the cyanobacterial MGDG biosynthesis pathway in a model cyanobacterium, Synechococcus elongatus PCC 7942, with the corresponding plant-type pathway. No obvious phenotype was observed under the optimum growth condition, and the content of membrane lipids was not largely altered in the transformants. We next replaced the cyanobacterial DGDG biosynthesis pathway with the corresponding plant-type pathway using the strain described above and isolated the strain harboring the replaced plant-type pathway instead of the whole Galactolipid biosynthesis pathway. This transformant, SeGPT, can grow photoautotrophically, indicating that cyanobacterial Galactolipid biosynthesis pathways can be functionally complemented by the corresponding plant-type pathways and that the lipid products MGDG and DGDG, and not biosynthesis pathways, are important. While SeGPT does not show strong growth retardation, the strain has low cellular chlorophyll content but it retained a similar oxygen evolution rate per chlorophyll content compared with the wild type. An increase in total membrane lipid content was observed in SeGPT, which was caused by a significant increase in DGDG content. SeGPT accumulated carotenoids from the xanthophyll groups. These results suggest that cyanobacteria have the capacity to accept other pathways to synthesize essential components of thylakoid membranes.
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an engineered lipid remodeling system using a Galactolipid synthase promoter during phosphate starvation enhances oil accumulation in plants
Frontiers in Plant Science, 2015Co-Authors: Mie Shimojima, Yuka Madoka, Ryota Fujiwara, Masato Murakawa, Yushi Yoshitake, Keiko Ikeda, Ryota Koizumi, Keiji Endo, Katsuya Ozaki, Hiroyuki OhtaAbstract:Inorganic phosphate (Pi) depletion is a serious problem for plant growth. Membrane lipid remodeling is a defense mechanism that plants use to survive Pi-depleted conditions. During Pi starvation, phospholipids are degraded to supply Pi for other essential biological processes, whereas Galactolipid synthesis in plastids is up-regulated via the transcriptional activation of monogalactosyldiacylglycerol synthase 3 (MGD3). Thus, the produced Galactolipids are transferred to extraplastidial membranes to substitute for phospholipids. We found that, Pi starvation induced oil accumulation in the vegetative tissues of various seed plants without activating the transcription of enzymes involved in the later steps of triacylglycerol (TAG) biosynthesis. Moreover, the Arabidopsis starchless phosphoglucomutase mutant, pgm-1, accumulated higher TAG levels than did wild-type plants under Pi-depleted conditions. We generated transgenic plants that expressed a key gene involved in TAG synthesis using the Pi deficiency-responsive MGD3 promoter in wild-type and pgm-1 backgrounds. During Pi starvation, the transgenic plants accumulated higher TAG amounts compared with the non-transgenic plants, suggesting that the Pi deficiency-responsive promoter of Galactolipid synthase in plastids may be useful for producing transgenic plants that accumulate more oil under Pi-depleted conditions.
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phylogeny of Galactolipid synthase homologs together with their enzymatic analyses revealed a possible origin and divergence time for photosynthetic membrane biogenesis
DNA Research, 2012Co-Authors: Yuichi Yuzawa, Mie Shimojima, Hidenori Nishihara, Tsuyoshi Haraguchi, Shinji Masuda, Atsushi Shimoyama, Hideya Yuasa, Norihiro Okada, Hiroyuki OhtaAbstract:The photosynthetic membranes of cyanobacteria and chloroplasts of higher plants have remarkably similar lipid compositions. In particular, thylakoid membranes of both cyanobacteria and chloroplasts are composed of Galactolipids, of which monogalactosyldiacylglycerol (MGDG) is the most abundant, although MGDG biosynthetic pathways are different in these organisms. Comprehensive phylogenetic analysis revealed that MGDG synthase (MGD) homologs of filamentous anoxygenic phototrophs Chloroflexi have a close relationship with MGDs of Viridiplantae (green algae and land plants). Furthermore, analyses for the sugar specificity and anomeric configuration of the sugar head groups revealed that one of the MGD homologs exhibited a true MGDG synthetic activity. We therefore presumed that higher plant MGDs are derived from this ancestral type of MGD genes, and genes involved in membrane biogenesis and photosystems have been already functionally associated at least at the time of Chloroflexi divergence. As MGD gene duplication is an important event during plastid evolution, we also estimated the divergence time of type A and B MGDs. Our analysis indicated that these genes diverged ∼323 million years ago, when Spermatophyta (seed plants) were appearing. Galactolipid synthesis is required to produce photosynthetic membranes; based on MGD gene sequences and activities, we have proposed a novel evolutionary model that has increased our understanding of photosynthesis evolution.
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critical regulation of Galactolipid synthesis controls membrane differentiation and remodeling in distinct plant organs and following environmental changes
Progress in Lipid Research, 2011Co-Authors: Mie Shimojima, Hiroyuki OhtaAbstract:The plant Galactolipids, monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), are the most abundant lipids in chloroplast membranes, and they constitute the majority of total membrane lipids in plants. MGDG is synthesized by two types of MGDG synthase, type-A (MGD1) and type-B (MGD2, MGD3). These MGDG synthases have distinct roles in Arabidopsis. In photosynthetic organs, Type A MGD is responsible for the bulk of MGDG synthesis, whereas Type B MGD is expressed in non-photosynthetic organs such as roots and flowers and mainly contributes to DGDG accumulation under phosphate deficiency. Similar to MGDG synthesis, DGDG is synthesized by two synthases, DGD1 and DGD2; DGD1 is responsible for the majority of DGDG synthesis, whereas DGD2 makes its main contribution under phosphate deficiency. These Galactolipid synthases are regulated by light, plant hormones, redox state, phosphatidic acid levels, and various stress conditions such as drought and nutrient limitation. Maintaining the appropriate ratio of these two Galactolipids in chloroplasts is important for stabilizing thylakoid membranes and maximizing the efficiency of photosynthesis. Here we review progress made in the last decade towards a better understanding of the pathways regulating plant Galactolipid biosynthesis.
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Phylogeny of Galactolipid Synthase Homologs Together with their Enzymatic Analyses Revealed a Possible Origin and Divergence Time for Photosynthetic Membrane Biogenesis
2011Co-Authors: Yuichi Yuzawa, Mie Shimojima, Hidenori Nishihara, Tsuyoshi Haraguchi, Shinji Masuda, Atsushi Shimoyama, Hideya Yuasa, Norihiro Okada, Hiroyuki OhtaAbstract:The photosynthetic membranes of cyanobacteria and chloroplasts of higher plants have remarkably similar lipid compositions. In particular, thylakoid membranes of both cyanobacteria and chloroplasts are composed of Galactolipids, of which monogalactosyldiacylglycerol (MGDG) is the most abundant, al-though MGDG biosynthetic pathways are different in these organisms. Comprehensive phylogenetic ana-lysis revealed that MGDG synthase (MGD) homologs of filamentous anoxygenic phototrophs Chloroflexi have a close relationship with MGDs of Viridiplantae (green algae and land plants). Furthermore, analyses for the sugar specificity and anomeric configuration of the sugar head groups revealed that one of the MGD homologs exhibited a true MGDG synthetic activity. We therefore presumed that higher plant MGDs are derived from this ancestral type of MGD genes, and genes involved in membrane biogenesis and photosystems have been already functionally associated at least at the time of Chloroflexi divergence. As MGD gene duplication is an important event during plastid evolution, we also estimated the divergence time of type A and B MGDs. Our analysis indicated that these genes diverged ∼323 million years ago, when Spermatophyta (seed plants) were appearing. Galactolipid synthesis is required to produce photo-synthetic membranes; based on MGD gene sequences and activities, we have proposed a novel evolution
