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Genetic Manipulation of Putrescine Biosynthesis Reprograms the Cellular Transcriptome and the Metabolome

ABSTRACT: Background: With the increasing interest in metabolic engineering of plants using various genetic manipulation and gene editing technologies in order to enhance their growth, nutritional value and environmental adaptation, a major concern is the potential of broad and distant effects of manipulating the target gene or the metabolic step in the resulting plant. A comprehensive transcriptomic and metabolomic analysis of the product may shed some useful light in this regard. The present study used these techniques with plant cell cultures to analyze the effects of genetic manipulation of a single step in the biosynthesis of polyamines because of their well-known roles in plant growth, development and stress responses [PMID 19383098] The transcriptomes and metabolomes of a control and a high putrescine producing (HP) cell line of poplar (Populus nigra x maximowiczii) were compared using microarrays and GC/MS. The HP cells expressed an ornithine decarboxylase transgene and accumulated several-fold higher concentrations of putrescine, with only small changes in spermidine and spermine. The results show that up-regulation of a single step in the polyamine biosynthetic pathway (i.e. ornithine→putrescine) altered the expression of a broad spectrum of genes; many of them were involved in transcription, translation, membrane transport, osmoregulation, shock/stress/wounding, and cell wall metabolism. More than half of the 200 detected metabolites were significantly altered (P <0.05) in the HP cells on any day of analysis; the most noteworthy differences were in organic acids, carbohydrates and nitrogen-containing metabolites. The results provide valuable information about the role of polyamines in regulating nitrogen and carbon use pathways in cell cultures of high putrescine producing transgenic cells of poplar vs. their low putrescine counterparts. The results underscore the complexity of cellular responses to genetic perturbation of a single metabolic step related to nitrogen metabolism in plants. Combined with recent studies from our lab regarding increased putrescine production causing an increased flux of glutamate into ornithine, with accompanied increase in glutamate production by additional nitrogen and carbon assimilation; the results may be useful in designing transgenic plants with increased nitrogen use efficiency, especially in plants intended for non-food/feed applications (e.g. increased biomass production or for biofuels).

ORGANISM(S): Populus tremula x Populus alba Populus maximowiczii x Populus nigra Populus trichocarpa x Populus deltoides Populus euphratica

PROVIDER: GSE79420 | GEO | 2016/03/24

SECONDARY ACCESSION(S): PRJNA316127

REPOSITORIES: GEO

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Project description:Background: With the increasing interest in metabolic engineering of plants using various genetic manipulation and gene editing technologies in order to enhance their growth, nutritional value and environmental adaptation, a major concern is the potential of broad and distant effects of manipulating the target gene or the metabolic step in the resulting plant. A comprehensive transcriptomic and metabolomic analysis of the product may shed some useful light in this regard. The present study used these techniques with plant cell cultures to analyze the effects of genetic manipulation of a single step in the biosynthesis of polyamines because of their well-known roles in plant growth, development and stress responses [PMID 19383098] The transcriptomes and metabolomes of a control and a high putrescine producing (HP) cell line of poplar (Populus nigra x maximowiczii) were compared using microarrays and GC/MS. The HP cells expressed an ornithine decarboxylase transgene and accumulated several-fold higher concentrations of putrescine, with only small changes in spermidine and spermine. The results show that up-regulation of a single step in the polyamine biosynthetic pathway (i.e. ornithineâputrescine) altered the expression of a broad spectrum of genes; many of them were involved in transcription, translation, membrane transport, osmoregulation, shock/stress/wounding, and cell wall metabolism. More than half of the 200 detected metabolites were significantly altered (P <0.05) in the HP cells on any day of analysis; the most noteworthy differences were in organic acids, carbohydrates and nitrogen-containing metabolites. The results provide valuable information about the role of polyamines in regulating nitrogen and carbon use pathways in cell cultures of high putrescine producing transgenic cells of poplar vs. their low putrescine counterparts. The results underscore the complexity of cellular responses to genetic perturbation of a single metabolic step related to nitrogen metabolism in plants. Combined with recent studies from our lab regarding increased putrescine production causing an increased flux of glutamate into ornithine, with accompanied increase in glutamate production by additional nitrogen and carbon assimilation; the results may be useful in designing transgenic plants with increased nitrogen use efficiency, especially in plants intended for non-food/feed applications (e.g. increased biomass production or for biofuels). 12 two-channel arrays directly comparing RNA from control and high putrescine producing (HP) cell lines of Populus nigra x maximowiczii at 3 and 5 days of growth. Three independent biological replicates derived from cells grown in three independent replicate cultures were used. In addition, each sample and time point included dye swap reciprocal two-color experiments for each biological replicate. Thus, six data points per cDNA are included (three biological replicates with two technical replicates each). Please note that experiments were technically carried out as dual channel (eg, Cy3 and Cy5-labeled samples hybridized to the same array; barcode ID for each array is indicated in the sample title and raw data file names) but two idependent raw data files were generated from each slide (one for Cy3, the other for Cy5) and processed as though they are single channel (Cy3 and Cy5 signals are calculated and provided for each sample record). Therfore, each sample record is represented as single channel sample.

Project description:Polyamines (putrescine, spermidine, and spermine) are major organic polycations essential for a wide spectrum of cellular processes. The cells require mechanisms to maintain homeostasis of intracellular polyamines to prevent otherwise severe adverse effects. We performed a detailed transcriptome profile analysis of P. aeruginosa in response to agmatine and putrescine with an emphasis in polyamine catabolism. Agmatine serves as precursor compound for putrescine (and hence spermidine and spermine), which was proposed to convert into GABA and succinate before entering the TCA cycle in support of cell growth as the sole source of carbon and nitrogen. Two acetylpolyamine amidohydrolases, AphA and AphB, were identified to be involved in the conversion of agmatine into putrescine. Enzymatic products of AphA were confirmed by mass spectrometry analysis. Interestingly, the alanine-pyruvate cycle was shown indispensable for polyamine utilization. The newly identified dadRAX locus, encoding the regulator, alanine transaminase and racemase respectively, coupled with SpuC, the major putrescine-pyruvate transaminase, were key components to maintain alanine homeostasis. Corresponding mutant strains were severely hampered in polyamine utilization. On the other hand, the alternative gamma-glutamylation pathway for the conversion of putrescine into GABA was also discussed. Subsequently, GabD, GabT and PA5313 were identified for GABA utilization. Growth defect of PA5313 gabT double mutant in GABA suggested the importance of these two transaminases. The succinic-semialdehyde dehydrogenase activity of GabD and its induction by GABA was also demonstrated in vitro. Polyamine utilization in general was proven independent of the PhoPQ two-component system even the expression of which was induced by polyamines. Multiple potent catabolic pathways as depicted in this study could serve pivotal roles in control of intracellular polyamine levels. Experiment Overall Design: P. aeruginosa PAO1 was grown aerobically in minimal medium P with 350 rpm shaking at 37C, in the presence of L-glutamate alone or with the addition of putrescine, agmatine or GABA at 20 mM. Cells were harvested when the optical density at 600 nm reached 0.5~0.6 by centrifugation for 5 minutes at 4C. Total RNA samples were isolated by RNeasy purification kit following instructions of the manufacturer (Qiagen). Reverse transcription for cDNA synthesis, fragmentation by DNase I treatment, cDNA probe labeling and hybridization were performed according to the instructions of GeneChip manufacturer (Affymetrix). Data were processed by Microarray Suite 5.0 software normalizing the absolute expression signal values of all chips to a target intensity of 500. GeneSpring software (Silicon Genetics) was used for expression pattern analysis and comparison. Only genes showing consistent expression profiles in duplicates were selected for further analysis.

Project description:Polyamines are aliphatic polycations that have emerged as important determinants of cell growth and viability in rapidly proliferating cells, including in the pathogenic protozoan parasite Leishmania donovani. In L. donovani, the polyamine spermidine is synthesized by the successive conversion of ornithine into putrescine (catalyzed by ornithine decarboxylase or ODC) and putrescine into spermidine (catalyzed by spermidine synthase or SPDSYN). Deletion of either ODC (del-odc) or SPDSYN (del-spdsyn) from the L. donovani genome renders these parasites auxotrophic for polyamines and these mutants are impaired in their ability to survive both in culture and within the mammalian host without the addition of exogenous polyamine supplementation. Significantly, del-odc parasites immediately cease proliferation after putrescine is removed from the culture media and perish within two weeks, while spermidine starved del-spdsyn mutants, which retain intracellular putrescine pools, show a slow-growth phenotype, and persist for several weeks in culture. To elucidate the key differences within the proteome of putrescine-starved del-odc cells and spermidine-starved del-spdsyn parasites, a shotgun quantitative proteomics approach was undertaken using TMT labeling and LC-MS/MS analysis. Briefly, three biological replicates each for mid-log phase del-odc and del-spdsyn promastigotes grown in the presence of exogenous putrescine (for del-odc) or spermidine (for del-spdsyn) supplementation were washed to remove the exogenous polyamine supplementation and incubated in polyamine-free media. At 24 and 48 h, cells from each biological replicate were isolated and prepared for tandem mass tag (TMT) labeling and downstream LC-MS/MS analyses. Peptides were identified using a database generated from the reference genome of L. donovani BPK282A1 strain. Changes in relative protein abundance for the polyamine-starved del-odc and del-spdsyn cell lines at 24 and 48 h were calculated by comparing aggregate total reporter ion intensities for each protein to that of the corresponding polyamine-supplemented 0-h timepoint.

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Genetic Manipulation of Putrescine Biosynthesis Reprograms the Cellular Transcriptome and the Metabolome

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