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Trevor A Thorpe - One of the best experts on this subject based on the ideXlab platform.
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changes in the de novo salvage and degradation pathways of pyrimidine nucleotides during tobacco shoot organogenesis
Plant Physiology and Biochemistry, 2008Co-Authors: Natalia Loukanina, Claudio Stasolla, Edward C Yeung, Mark F Belmonte, Trevor A ThorpeAbstract:Abstract Pyrimidine nucleotide metabolism was studied in tobacco callus cultured for 21 days under shoot-forming (SF) and non-shoot-forming (NSF) conditions by following the metabolic fate of orotic Acid, a precursor of the de novo pathway, and uridine and uracil, intermediates of the salvage and degradation pathways respectively. Nucleic Acid Synthesis was also investigated by measuring the incorporation of labeled thymidine into different cellular components. Our results indicate that with respect to nucleotide metabolism, the organogenic process in tobacco can be divided in two “metabolic phases”: a de novo phase followed by a salvage phase. The initial stages of meristemoid formation during tobacco organogenesis (up to day 8) are characterized by a heavy utilization of orotic Acid into nucleotides and Nucleic Acids. Utilization of this intermediate for the de novo Synthesis of nucleotides, which is limited in NSF tissue, is mainly due to the activity of orotate phosphoribosyltransferase (OPRT), which increases in tissue cultured under SF conditions. After day 8, nucleotide Synthesis during shoot growth seems to be mainly due to the salvage activity of both uridine and uracil. Both intermediates are preferentially utilized in SF tissue for the formation of nucleotides and Nucleic Acids through the activities of their respective salvage enzymes: uridine kinase (URK), and uracil phosphoribosyltransferase (UPRT). Metabolic studies on thymidine indicate that in SF tissue maximal Nucleic Acid Synthesis occurs at day 4, in support of the initiation of meristemoid formation. Overall these results suggest that the organogenic process in tobacco is underlined by precise fluctuations in pyrimidine metabolism which delineate structural events culminating in shoot formation.
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comparative studies on pyrimidine metabolism in excised cotyledons of pinus radiata during shoot formation in vitro
Journal of Plant Physiology, 2007Co-Authors: Claudio Stasolla, Natalia Loukanina, Edward C Yeung, Hiroshi Ashihara, Trevor A ThorpeAbstract:Summary Changes in the pattern of pyrimidine nucleotide metabolism were investigated in Pinus radiata cotyledons cultured under shoot-forming (SF; +N 6 -benzyladenine) and non-shoot-forming (NSF, −N 6 -benzyladenine) conditions, as well as in cotyledons unresponsive (OLD) to N 6 -benzyladenine. This was carried out by following the metabolic fate of externally supplied 14 C-labeled orotic Acid, intermediate of the de novo pathway, and 14 C-labeled uridine and uracil, substrates of the salvage pathway. Nucleic Acid Synthesis was also investigated by following the metabolic fate of 14 C-labeled thymidine during shoot bud formation and development. The de novo Synthesis of pyrimidine nucleotides was operative under both SF and NSF conditions, and the activity of orotate phosphoribosyltransferase (OPRT), a key enzyme of the de novo pathway, was higher in SF tissue. Utilization of both uridine and uracil for nucleotide and Nucleic Acid Synthesis clearly indicated that the salvage pathway of pyrimidine metabolism is also operative during shoot organogenesis. In general, uridine was a better substrate for the Synthesis of salvage products than uracil, possibly due to the higher activity of uridine kinase (UK), compared to uracil phosphoribosyltransferase (UPRT). Incorporation of uridine into the Nucleic Acid fraction of OLD cotyledons was lower than that observed for their responsive (day 0) counterparts. Similarly, uracil utilization for Nucleic Acid Synthesis was lower in NSF cotyledons, compared to that observed for SF tissue after 10 days in culture. This difference was ascribed to higher UPRT activity measured in the latter. Thus, there was an apparent difference in the utilization of nucleotides derived from uracil and uridine for nucleotide Synthesis. The increased ability to produce pyrimidine nucleotides via the salvage pathway during shoot bud formation may be required in support of Nucleic Acid Synthesis occurring during the process. Studies on thymidine metabolism confirmed this notion.
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changes of purine and pyrimidine nucleotide bioSynthesis during shoot initiation from epicotyl explants of white spruce picea glauca
Plant Science, 2006Co-Authors: Claudio Stasolla, Natalia Loukanina, Edward C Yeung, Hiroshi Ashihara, Trevor A ThorpeAbstract:Abstract Nucleotide metabolism was investigated during white spruce organogenesis by following the metabolic fate of 14C-labeled adenine, adenosine and inosine, as purine precursors, and orotic Acid, uridine, and uracil, as pyrimidine intermediates. Key enzymes of purine and pyrimidine metabolism were also assayed during the organogenic process. White spruce epicotyl explants cultured on shoot-forming (SF) medium had a better ability to utilize adenine and adenosine for nucleotide and Nucleic Acid Synthesis, compared to tissue cultured on non-shoot forming (NSF) medium. High levels of salvage products were observed in SF tissue after 10 days in culture, when shoot formation was initiated along the epicotyl axis of the explants. Such a differential utilization of purine precursors was mainly due to the higher specific activity of the two adenine and adenosine salvage enzymes, adenine phosphoribosyltransferase (APRT) and adenosine kinase (AK), measured in SF tissue. Similar catabolism of inosine was observed in both SF and NSF conditions during the 30 days of culture. For pyrimidines, the higher activities of the de novo, salvage, and degradation pathways observed in SF tissue, compared to NSF tissue throughout the course of the experiment, clearly denote a faster turnover of pyrimidine nucleotides in the former. Taken together, these results suggest that a better utilization of purine bases and nucleosides for nucleotide and Nucleic Acid Synthesis, as well as a more rapid turnover of pyrimidine nucleotides, represent a physiological switch, which occurs during the initiation and continuation of the organogenic process in white spruce.
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purine and pyrimidine nucleotide metabolism in higher plants
Journal of Plant Physiology, 2003Co-Authors: Claudio Stasolla, Riko Katahira, Trevor A ThorpeAbstract:Purine and pyrimidine nucleotides participate in many biochemical processes in plants. They are building blocks for Nucleic Acid Synthesis, an energy source, precursors for the Synthesis of primary products, such as sucrose, polysaccharides, phospholipids, as well as secondary products. Therefore, bioSynthesis and metabolism of nucleotides are of fundamental importance in the growth and development of plants. Nucleotides are synthesized both from amino Acids and other small molecules via de novo pathways, and from preformed nucleobases and nucleosides by salvage pathways. In this article the bioSynthesis, interconversion and degradation of purine and pyrimidine nucleotides in higher plants are reviewed. This description is followed by an examination of physiological aspects of nucleotide metabolism in various areas of growth and organized development in plants, including embryo maturation and germination, in vitro organogenesis, storage organ development and sprouting, leaf senescence, and cultured plant cells. The effects of environmental factors on nucleotide metabolism are also described. This review ends with a brief discussion of molecular studies on nucleotide Synthesis and metabolism.
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pyrimidine nucleotide and Nucleic Acid Synthesis in embryos and megagametophytes of white spruce picea glauca during germination
Physiologia Plantarum, 2002Co-Authors: Claudio Stasolla, Natalia Loukanina, Edward C Yeung, Trevor A ThorpeAbstract:Pyrimidine nucleotide Synthesis was investigated in isolated germinating zygotic embryos and separated megagametophytes of white spruce by following the metabolic fate of 14C-labelled orotic Acid, uridine, and uracil, as well as by measuring the activities of the major enzymes participating in nucleotide Synthesis. The rate of Nucleic Acid Synthesis in these tissues was also examined by tracer experiments and autoradiographic studies conducted with labelled thymidine, and by conventional light microscopy. From our results, it emerges that changes in the contribution of the de novo and salvage pathways of pyrimidines play an important role during the initial stages of zygotic embryo germination. Preferential utilization of uridine for Nucleic Acid Synthesis, via the salvage pathway, was observed at the onset of germination, before the restoration of a fully functional de novo pathway. Similar metabolic changes, not observed in the gametophytic tissue, were also documented in somatic embryos previously. These alterations of the overall pyrimidine metabolism may represent a strategy for ensuring the germinating embryos with a large nucleotide pool. Utilization of 14C-thymidine for Nucleic Acid Synthesis increased in both dissected embryos and megagametophytes during germination. Autoradiographic and light microscopic studies indicated that soon after imbibition, DNA Synthesis was preferentially initiated along the embryonic axis, especially in the cortical cells. Apical meristem reactivation was a later event, and the root meristem became activated before the shoot meristem. Taken together, these results indicate that precise changes in nucleotide and Nucleic Acid metabolism occur during the early phases of embryo germination.
Claudio Stasolla - One of the best experts on this subject based on the ideXlab platform.
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changes in the de novo salvage and degradation pathways of pyrimidine nucleotides during tobacco shoot organogenesis
Plant Physiology and Biochemistry, 2008Co-Authors: Natalia Loukanina, Claudio Stasolla, Edward C Yeung, Mark F Belmonte, Trevor A ThorpeAbstract:Abstract Pyrimidine nucleotide metabolism was studied in tobacco callus cultured for 21 days under shoot-forming (SF) and non-shoot-forming (NSF) conditions by following the metabolic fate of orotic Acid, a precursor of the de novo pathway, and uridine and uracil, intermediates of the salvage and degradation pathways respectively. Nucleic Acid Synthesis was also investigated by measuring the incorporation of labeled thymidine into different cellular components. Our results indicate that with respect to nucleotide metabolism, the organogenic process in tobacco can be divided in two “metabolic phases”: a de novo phase followed by a salvage phase. The initial stages of meristemoid formation during tobacco organogenesis (up to day 8) are characterized by a heavy utilization of orotic Acid into nucleotides and Nucleic Acids. Utilization of this intermediate for the de novo Synthesis of nucleotides, which is limited in NSF tissue, is mainly due to the activity of orotate phosphoribosyltransferase (OPRT), which increases in tissue cultured under SF conditions. After day 8, nucleotide Synthesis during shoot growth seems to be mainly due to the salvage activity of both uridine and uracil. Both intermediates are preferentially utilized in SF tissue for the formation of nucleotides and Nucleic Acids through the activities of their respective salvage enzymes: uridine kinase (URK), and uracil phosphoribosyltransferase (UPRT). Metabolic studies on thymidine indicate that in SF tissue maximal Nucleic Acid Synthesis occurs at day 4, in support of the initiation of meristemoid formation. Overall these results suggest that the organogenic process in tobacco is underlined by precise fluctuations in pyrimidine metabolism which delineate structural events culminating in shoot formation.
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comparative studies on pyrimidine metabolism in excised cotyledons of pinus radiata during shoot formation in vitro
Journal of Plant Physiology, 2007Co-Authors: Claudio Stasolla, Natalia Loukanina, Edward C Yeung, Hiroshi Ashihara, Trevor A ThorpeAbstract:Summary Changes in the pattern of pyrimidine nucleotide metabolism were investigated in Pinus radiata cotyledons cultured under shoot-forming (SF; +N 6 -benzyladenine) and non-shoot-forming (NSF, −N 6 -benzyladenine) conditions, as well as in cotyledons unresponsive (OLD) to N 6 -benzyladenine. This was carried out by following the metabolic fate of externally supplied 14 C-labeled orotic Acid, intermediate of the de novo pathway, and 14 C-labeled uridine and uracil, substrates of the salvage pathway. Nucleic Acid Synthesis was also investigated by following the metabolic fate of 14 C-labeled thymidine during shoot bud formation and development. The de novo Synthesis of pyrimidine nucleotides was operative under both SF and NSF conditions, and the activity of orotate phosphoribosyltransferase (OPRT), a key enzyme of the de novo pathway, was higher in SF tissue. Utilization of both uridine and uracil for nucleotide and Nucleic Acid Synthesis clearly indicated that the salvage pathway of pyrimidine metabolism is also operative during shoot organogenesis. In general, uridine was a better substrate for the Synthesis of salvage products than uracil, possibly due to the higher activity of uridine kinase (UK), compared to uracil phosphoribosyltransferase (UPRT). Incorporation of uridine into the Nucleic Acid fraction of OLD cotyledons was lower than that observed for their responsive (day 0) counterparts. Similarly, uracil utilization for Nucleic Acid Synthesis was lower in NSF cotyledons, compared to that observed for SF tissue after 10 days in culture. This difference was ascribed to higher UPRT activity measured in the latter. Thus, there was an apparent difference in the utilization of nucleotides derived from uracil and uridine for nucleotide Synthesis. The increased ability to produce pyrimidine nucleotides via the salvage pathway during shoot bud formation may be required in support of Nucleic Acid Synthesis occurring during the process. Studies on thymidine metabolism confirmed this notion.
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changes of purine and pyrimidine nucleotide bioSynthesis during shoot initiation from epicotyl explants of white spruce picea glauca
Plant Science, 2006Co-Authors: Claudio Stasolla, Natalia Loukanina, Edward C Yeung, Hiroshi Ashihara, Trevor A ThorpeAbstract:Abstract Nucleotide metabolism was investigated during white spruce organogenesis by following the metabolic fate of 14C-labeled adenine, adenosine and inosine, as purine precursors, and orotic Acid, uridine, and uracil, as pyrimidine intermediates. Key enzymes of purine and pyrimidine metabolism were also assayed during the organogenic process. White spruce epicotyl explants cultured on shoot-forming (SF) medium had a better ability to utilize adenine and adenosine for nucleotide and Nucleic Acid Synthesis, compared to tissue cultured on non-shoot forming (NSF) medium. High levels of salvage products were observed in SF tissue after 10 days in culture, when shoot formation was initiated along the epicotyl axis of the explants. Such a differential utilization of purine precursors was mainly due to the higher specific activity of the two adenine and adenosine salvage enzymes, adenine phosphoribosyltransferase (APRT) and adenosine kinase (AK), measured in SF tissue. Similar catabolism of inosine was observed in both SF and NSF conditions during the 30 days of culture. For pyrimidines, the higher activities of the de novo, salvage, and degradation pathways observed in SF tissue, compared to NSF tissue throughout the course of the experiment, clearly denote a faster turnover of pyrimidine nucleotides in the former. Taken together, these results suggest that a better utilization of purine bases and nucleosides for nucleotide and Nucleic Acid Synthesis, as well as a more rapid turnover of pyrimidine nucleotides, represent a physiological switch, which occurs during the initiation and continuation of the organogenic process in white spruce.
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purine and pyrimidine nucleotide metabolism in higher plants
Journal of Plant Physiology, 2003Co-Authors: Claudio Stasolla, Riko Katahira, Trevor A ThorpeAbstract:Purine and pyrimidine nucleotides participate in many biochemical processes in plants. They are building blocks for Nucleic Acid Synthesis, an energy source, precursors for the Synthesis of primary products, such as sucrose, polysaccharides, phospholipids, as well as secondary products. Therefore, bioSynthesis and metabolism of nucleotides are of fundamental importance in the growth and development of plants. Nucleotides are synthesized both from amino Acids and other small molecules via de novo pathways, and from preformed nucleobases and nucleosides by salvage pathways. In this article the bioSynthesis, interconversion and degradation of purine and pyrimidine nucleotides in higher plants are reviewed. This description is followed by an examination of physiological aspects of nucleotide metabolism in various areas of growth and organized development in plants, including embryo maturation and germination, in vitro organogenesis, storage organ development and sprouting, leaf senescence, and cultured plant cells. The effects of environmental factors on nucleotide metabolism are also described. This review ends with a brief discussion of molecular studies on nucleotide Synthesis and metabolism.
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pyrimidine nucleotide and Nucleic Acid Synthesis in embryos and megagametophytes of white spruce picea glauca during germination
Physiologia Plantarum, 2002Co-Authors: Claudio Stasolla, Natalia Loukanina, Edward C Yeung, Trevor A ThorpeAbstract:Pyrimidine nucleotide Synthesis was investigated in isolated germinating zygotic embryos and separated megagametophytes of white spruce by following the metabolic fate of 14C-labelled orotic Acid, uridine, and uracil, as well as by measuring the activities of the major enzymes participating in nucleotide Synthesis. The rate of Nucleic Acid Synthesis in these tissues was also examined by tracer experiments and autoradiographic studies conducted with labelled thymidine, and by conventional light microscopy. From our results, it emerges that changes in the contribution of the de novo and salvage pathways of pyrimidines play an important role during the initial stages of zygotic embryo germination. Preferential utilization of uridine for Nucleic Acid Synthesis, via the salvage pathway, was observed at the onset of germination, before the restoration of a fully functional de novo pathway. Similar metabolic changes, not observed in the gametophytic tissue, were also documented in somatic embryos previously. These alterations of the overall pyrimidine metabolism may represent a strategy for ensuring the germinating embryos with a large nucleotide pool. Utilization of 14C-thymidine for Nucleic Acid Synthesis increased in both dissected embryos and megagametophytes during germination. Autoradiographic and light microscopic studies indicated that soon after imbibition, DNA Synthesis was preferentially initiated along the embryonic axis, especially in the cortical cells. Apical meristem reactivation was a later event, and the root meristem became activated before the shoot meristem. Taken together, these results indicate that precise changes in nucleotide and Nucleic Acid metabolism occur during the early phases of embryo germination.
Shivendra G Tewari - One of the best experts on this subject based on the ideXlab platform.
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short term metabolic adjustments in plasmodium falciparum counter hypoxanthine deprivation at the expense of long term viability
Malaria Journal, 2019Co-Authors: Shivendra G Tewari, Krithika Rajaram, Patric Schyman, Russell P Swift, Jaques Reifman, Sean T Prigge, Anders WallqvistAbstract:The malarial parasite Plasmodium falciparum is an auxotroph for purines, which are required for Nucleic Acid Synthesis during the intra-erythrocytic developmental cycle (IDC) of the parasite. The capabilities of the parasite and extent to which it can use compensatory mechanisms to adapt to purine deprivation were studied by examining changes in its metabolism under sub-optimal concentrations of hypoxanthine, the primary precursor utilized by the parasite for purine-based Nucleic Acid Synthesis. The concentration of hypoxanthine that caused a moderate growth defect over the course of one IDC was determined. At this concentration of hypoxanthine (0.5 μM), transcriptomic and metabolomic data were collected during one IDC at multiple time points. These data were integrated with a metabolic network model of the parasite embedded in a red blood cell (RBC) to interpret the metabolic adaptation of P. falciparum to hypoxanthine deprivation. At a hypoxanthine concentration of 0.5 μM, vacuole-like structures in the cytosol of many P. falciparum parasites were observed after the 24-h midpoint of the IDC. Parasites grown under these conditions experienced a slowdown in the progression of the IDC. After 72 h of deprivation, the parasite growth could not be recovered despite supplementation with 90 µM hypoxanthine. Simulations of P. falciparum metabolism suggested that alterations in ubiquinone, isoprenoid, shikimate, and mitochondrial metabolism occurred before the appearance of these vacuole-like structures. Alterations were found in metabolic reactions associated with fatty Acid Synthesis, the pentose phosphate pathway, methionine metabolism, and coenzyme A Synthesis in the latter half of the IDC. Furthermore, gene set enrichment analysis revealed that P. falciparum activated genes associated with rosette formation, Maurer’s cleft and protein export under two different nutrient-deprivation conditions (hypoxanthine and isoleucine). The metabolic network analysis presented here suggests that P. falciparum invokes specific purine-recycling pathways to compensate for hypoxanthine deprivation and maintains a hypoxanthine pool for purine-based Nucleic Acid Synthesis. However, this compensatory mechanism is not sufficient to maintain long-term viability of the parasite. Although P. falciparum can complete a full IDC in low hypoxanthine conditions, subsequent cycles are disrupted.
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Short-term metabolic adjustments in Plasmodium falciparum counter hypoxanthine deprivation at the expense of long-term viability
BMC, 2019Co-Authors: Shivendra G Tewari, Krithika Rajaram, Patric Schyman, Jaques Reifman, Sean T Prigge, Russell Swift, Anders WallqvistAbstract:Abstract Background The malarial parasite Plasmodium falciparum is an auxotroph for purines, which are required for Nucleic Acid Synthesis during the intra-erythrocytic developmental cycle (IDC) of the parasite. The capabilities of the parasite and extent to which it can use compensatory mechanisms to adapt to purine deprivation were studied by examining changes in its metabolism under sub-optimal concentrations of hypoxanthine, the primary precursor utilized by the parasite for purine-based Nucleic Acid Synthesis. Methods The concentration of hypoxanthine that caused a moderate growth defect over the course of one IDC was determined. At this concentration of hypoxanthine (0.5 μM), transcriptomic and metabolomic data were collected during one IDC at multiple time points. These data were integrated with a metabolic network model of the parasite embedded in a red blood cell (RBC) to interpret the metabolic adaptation of P. falciparum to hypoxanthine deprivation. Results At a hypoxanthine concentration of 0.5 μM, vacuole-like structures in the cytosol of many P. falciparum parasites were observed after the 24-h midpoint of the IDC. Parasites grown under these conditions experienced a slowdown in the progression of the IDC. After 72 h of deprivation, the parasite growth could not be recovered despite supplementation with 90 µM hypoxanthine. Simulations of P. falciparum metabolism suggested that alterations in ubiquinone, isoprenoid, shikimate, and mitochondrial metabolism occurred before the appearance of these vacuole-like structures. Alterations were found in metabolic reactions associated with fatty Acid Synthesis, the pentose phosphate pathway, methionine metabolism, and coenzyme A Synthesis in the latter half of the IDC. Furthermore, gene set enrichment analysis revealed that P. falciparum activated genes associated with rosette formation, Maurer’s cleft and protein export under two different nutrient-deprivation conditions (hypoxanthine and isoleucine). Conclusions The metabolic network analysis presented here suggests that P. falciparum invokes specific purine-recycling pathways to compensate for hypoxanthine deprivation and maintains a hypoxanthine pool for purine-based Nucleic Acid Synthesis. However, this compensatory mechanism is not sufficient to maintain long-term viability of the parasite. Although P. falciparum can complete a full IDC in low hypoxanthine conditions, subsequent cycles are disrupted
Anders Wallqvist - One of the best experts on this subject based on the ideXlab platform.
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short term metabolic adjustments in plasmodium falciparum counter hypoxanthine deprivation at the expense of long term viability
Malaria Journal, 2019Co-Authors: Shivendra G Tewari, Krithika Rajaram, Patric Schyman, Russell P Swift, Jaques Reifman, Sean T Prigge, Anders WallqvistAbstract:The malarial parasite Plasmodium falciparum is an auxotroph for purines, which are required for Nucleic Acid Synthesis during the intra-erythrocytic developmental cycle (IDC) of the parasite. The capabilities of the parasite and extent to which it can use compensatory mechanisms to adapt to purine deprivation were studied by examining changes in its metabolism under sub-optimal concentrations of hypoxanthine, the primary precursor utilized by the parasite for purine-based Nucleic Acid Synthesis. The concentration of hypoxanthine that caused a moderate growth defect over the course of one IDC was determined. At this concentration of hypoxanthine (0.5 μM), transcriptomic and metabolomic data were collected during one IDC at multiple time points. These data were integrated with a metabolic network model of the parasite embedded in a red blood cell (RBC) to interpret the metabolic adaptation of P. falciparum to hypoxanthine deprivation. At a hypoxanthine concentration of 0.5 μM, vacuole-like structures in the cytosol of many P. falciparum parasites were observed after the 24-h midpoint of the IDC. Parasites grown under these conditions experienced a slowdown in the progression of the IDC. After 72 h of deprivation, the parasite growth could not be recovered despite supplementation with 90 µM hypoxanthine. Simulations of P. falciparum metabolism suggested that alterations in ubiquinone, isoprenoid, shikimate, and mitochondrial metabolism occurred before the appearance of these vacuole-like structures. Alterations were found in metabolic reactions associated with fatty Acid Synthesis, the pentose phosphate pathway, methionine metabolism, and coenzyme A Synthesis in the latter half of the IDC. Furthermore, gene set enrichment analysis revealed that P. falciparum activated genes associated with rosette formation, Maurer’s cleft and protein export under two different nutrient-deprivation conditions (hypoxanthine and isoleucine). The metabolic network analysis presented here suggests that P. falciparum invokes specific purine-recycling pathways to compensate for hypoxanthine deprivation and maintains a hypoxanthine pool for purine-based Nucleic Acid Synthesis. However, this compensatory mechanism is not sufficient to maintain long-term viability of the parasite. Although P. falciparum can complete a full IDC in low hypoxanthine conditions, subsequent cycles are disrupted.
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Short-term metabolic adjustments in Plasmodium falciparum counter hypoxanthine deprivation at the expense of long-term viability
BMC, 2019Co-Authors: Shivendra G Tewari, Krithika Rajaram, Patric Schyman, Jaques Reifman, Sean T Prigge, Russell Swift, Anders WallqvistAbstract:Abstract Background The malarial parasite Plasmodium falciparum is an auxotroph for purines, which are required for Nucleic Acid Synthesis during the intra-erythrocytic developmental cycle (IDC) of the parasite. The capabilities of the parasite and extent to which it can use compensatory mechanisms to adapt to purine deprivation were studied by examining changes in its metabolism under sub-optimal concentrations of hypoxanthine, the primary precursor utilized by the parasite for purine-based Nucleic Acid Synthesis. Methods The concentration of hypoxanthine that caused a moderate growth defect over the course of one IDC was determined. At this concentration of hypoxanthine (0.5 μM), transcriptomic and metabolomic data were collected during one IDC at multiple time points. These data were integrated with a metabolic network model of the parasite embedded in a red blood cell (RBC) to interpret the metabolic adaptation of P. falciparum to hypoxanthine deprivation. Results At a hypoxanthine concentration of 0.5 μM, vacuole-like structures in the cytosol of many P. falciparum parasites were observed after the 24-h midpoint of the IDC. Parasites grown under these conditions experienced a slowdown in the progression of the IDC. After 72 h of deprivation, the parasite growth could not be recovered despite supplementation with 90 µM hypoxanthine. Simulations of P. falciparum metabolism suggested that alterations in ubiquinone, isoprenoid, shikimate, and mitochondrial metabolism occurred before the appearance of these vacuole-like structures. Alterations were found in metabolic reactions associated with fatty Acid Synthesis, the pentose phosphate pathway, methionine metabolism, and coenzyme A Synthesis in the latter half of the IDC. Furthermore, gene set enrichment analysis revealed that P. falciparum activated genes associated with rosette formation, Maurer’s cleft and protein export under two different nutrient-deprivation conditions (hypoxanthine and isoleucine). Conclusions The metabolic network analysis presented here suggests that P. falciparum invokes specific purine-recycling pathways to compensate for hypoxanthine deprivation and maintains a hypoxanthine pool for purine-based Nucleic Acid Synthesis. However, this compensatory mechanism is not sufficient to maintain long-term viability of the parasite. Although P. falciparum can complete a full IDC in low hypoxanthine conditions, subsequent cycles are disrupted
Patric Schyman - One of the best experts on this subject based on the ideXlab platform.
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short term metabolic adjustments in plasmodium falciparum counter hypoxanthine deprivation at the expense of long term viability
Malaria Journal, 2019Co-Authors: Shivendra G Tewari, Krithika Rajaram, Patric Schyman, Russell P Swift, Jaques Reifman, Sean T Prigge, Anders WallqvistAbstract:The malarial parasite Plasmodium falciparum is an auxotroph for purines, which are required for Nucleic Acid Synthesis during the intra-erythrocytic developmental cycle (IDC) of the parasite. The capabilities of the parasite and extent to which it can use compensatory mechanisms to adapt to purine deprivation were studied by examining changes in its metabolism under sub-optimal concentrations of hypoxanthine, the primary precursor utilized by the parasite for purine-based Nucleic Acid Synthesis. The concentration of hypoxanthine that caused a moderate growth defect over the course of one IDC was determined. At this concentration of hypoxanthine (0.5 μM), transcriptomic and metabolomic data were collected during one IDC at multiple time points. These data were integrated with a metabolic network model of the parasite embedded in a red blood cell (RBC) to interpret the metabolic adaptation of P. falciparum to hypoxanthine deprivation. At a hypoxanthine concentration of 0.5 μM, vacuole-like structures in the cytosol of many P. falciparum parasites were observed after the 24-h midpoint of the IDC. Parasites grown under these conditions experienced a slowdown in the progression of the IDC. After 72 h of deprivation, the parasite growth could not be recovered despite supplementation with 90 µM hypoxanthine. Simulations of P. falciparum metabolism suggested that alterations in ubiquinone, isoprenoid, shikimate, and mitochondrial metabolism occurred before the appearance of these vacuole-like structures. Alterations were found in metabolic reactions associated with fatty Acid Synthesis, the pentose phosphate pathway, methionine metabolism, and coenzyme A Synthesis in the latter half of the IDC. Furthermore, gene set enrichment analysis revealed that P. falciparum activated genes associated with rosette formation, Maurer’s cleft and protein export under two different nutrient-deprivation conditions (hypoxanthine and isoleucine). The metabolic network analysis presented here suggests that P. falciparum invokes specific purine-recycling pathways to compensate for hypoxanthine deprivation and maintains a hypoxanthine pool for purine-based Nucleic Acid Synthesis. However, this compensatory mechanism is not sufficient to maintain long-term viability of the parasite. Although P. falciparum can complete a full IDC in low hypoxanthine conditions, subsequent cycles are disrupted.
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Short-term metabolic adjustments in Plasmodium falciparum counter hypoxanthine deprivation at the expense of long-term viability
BMC, 2019Co-Authors: Shivendra G Tewari, Krithika Rajaram, Patric Schyman, Jaques Reifman, Sean T Prigge, Russell Swift, Anders WallqvistAbstract:Abstract Background The malarial parasite Plasmodium falciparum is an auxotroph for purines, which are required for Nucleic Acid Synthesis during the intra-erythrocytic developmental cycle (IDC) of the parasite. The capabilities of the parasite and extent to which it can use compensatory mechanisms to adapt to purine deprivation were studied by examining changes in its metabolism under sub-optimal concentrations of hypoxanthine, the primary precursor utilized by the parasite for purine-based Nucleic Acid Synthesis. Methods The concentration of hypoxanthine that caused a moderate growth defect over the course of one IDC was determined. At this concentration of hypoxanthine (0.5 μM), transcriptomic and metabolomic data were collected during one IDC at multiple time points. These data were integrated with a metabolic network model of the parasite embedded in a red blood cell (RBC) to interpret the metabolic adaptation of P. falciparum to hypoxanthine deprivation. Results At a hypoxanthine concentration of 0.5 μM, vacuole-like structures in the cytosol of many P. falciparum parasites were observed after the 24-h midpoint of the IDC. Parasites grown under these conditions experienced a slowdown in the progression of the IDC. After 72 h of deprivation, the parasite growth could not be recovered despite supplementation with 90 µM hypoxanthine. Simulations of P. falciparum metabolism suggested that alterations in ubiquinone, isoprenoid, shikimate, and mitochondrial metabolism occurred before the appearance of these vacuole-like structures. Alterations were found in metabolic reactions associated with fatty Acid Synthesis, the pentose phosphate pathway, methionine metabolism, and coenzyme A Synthesis in the latter half of the IDC. Furthermore, gene set enrichment analysis revealed that P. falciparum activated genes associated with rosette formation, Maurer’s cleft and protein export under two different nutrient-deprivation conditions (hypoxanthine and isoleucine). Conclusions The metabolic network analysis presented here suggests that P. falciparum invokes specific purine-recycling pathways to compensate for hypoxanthine deprivation and maintains a hypoxanthine pool for purine-based Nucleic Acid Synthesis. However, this compensatory mechanism is not sufficient to maintain long-term viability of the parasite. Although P. falciparum can complete a full IDC in low hypoxanthine conditions, subsequent cycles are disrupted
