Carbon Partitioning in Green Algae (Chlorophyta) and the Enolase Enzyme

Polle, Jürgen E.W.; Neofotis, Peter; Huang, Andy; Chang, Wenguang; Sury, Kiran; Wiech, Eliza M.

doi:10.3390/metabo4030612

Cited by 24 publications

(23 citation statements)

References 67 publications

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“…The FC2 cells ascertained that the PEP is not a limiting factor for ATP and pyruvate generation by elevating the levels of a complementary glycolytic enzyme; ENL. PEP may serve as a precursor molecule for isoprenoid and glycerolipid biosynthesis through pyruvate and acetyl-CoA65. Interestingly, the abundance of ENL and PK is in accordance with the temporal lipid accumulation in N-starved FC2 cells as confirmed by nile red staining.…”

Section: Discussionmentioning

confidence: 56%

Real-time iTRAQ-based proteome profiling revealed the central metabolism involved in nitrogen starvation induced lipid accumulation in microalgae

Rai

Muthuraj

Gandhi

et al. 2017

Sci Rep

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To understand the post-transcriptional molecular mechanisms attributing to oleaginousness in microalgae challenged with nitrogen starvation (N-starvation), the longitudinal proteome dynamics of Chlorella sp. FC2 IITG was investigated using multipronged quantitative proteomics and multiple reaction monitoring assays. Physiological data suggested a remarkably enhanced lipid accumulation with concomitant reduction in carbon flux towards carbohydrate, protein and chlorophyll biosynthesis. The proteomics-based investigations identified the down-regulation of enzymes involved in chlorophyll biosynthesis (porphobilinogen deaminase) and photosynthetic carbon fixation (sedoheptulose-1,7 bisphosphate and phosphoribulokinase). Profound up-regulation of hydroxyacyl-ACP dehydrogenase and enoyl-ACP reductase ascertained lipid accumulation. The carbon skeletons to be integrated into lipid precursors were regenerated by glycolysis, β-oxidation and TCA cycle. The enhanced expression of glycolysis and pentose phosphate pathway enzymes indicates heightened energy needs of FC2 cells for the sustenance of N-starvation. FC2 cells strategically reserved nitrogen by incorporating it into the TCA-cycle intermediates to form amino acids; particularly the enzymes involved in the biosynthesis of glutamate, aspartate and arginine were up-regulated. Regulation of arginine, superoxide dismutase, thioredoxin-peroxiredoxin, lipocalin, serine-hydroxymethyltransferase, cysteine synthase, and octanoyltransferase play a critical role in maintaining cellular homeostasis during N-starvation. These findings may provide a rationale for genetic engineering of microalgae, which may enable synchronized biomass and lipid synthesis.

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Section: Discussionmentioning

confidence: 56%

Real-time iTRAQ-based proteome profiling revealed the central metabolism involved in nitrogen starvation induced lipid accumulation in microalgae

Rai

Muthuraj

Gandhi

et al. 2017

Sci Rep

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“…The lower part of glycolysis appears to occur exclusively in the cytosol in C . reinhardtii (Terashima et al ., ; Johnson and Alric, ; Polle et al ., ). Metabolites: 2PGA, 2‐phosphoglycerate; 3PGA, 3‐phosphoglycerate; DHA, dihydroxyacetone; DHAP, dihydroxyacetone phosphate; FFA, free fatty acid; G1P, glucose‐1‐phosphate; G3P, glycerol‐3‐phosphate; GAP, glyceraldehyde‐3‐phosphate; Gly, glycerol; PEP, phosphoenolpyruvate; Pyr, pyruvate.…”

Section: Resultsmentioning

confidence: 97%

A multidomain enzyme, with glycerol‐3‐phosphate dehydrogenase and phosphatase activities, is involved in a chloroplastic pathway for glycerol synthesis in Chlamydomonas reinhardtii

et al. 2017

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Summary Understanding the unique features of algal metabolism may be necessary to realize the full potential of algae as feedstock for the production of biofuels and biomaterials. Under nitrogen deprivation, the green alga C. reinhardtii showed substantial triacylglycerol (TAG) accumulation and up‐regulation of a gene, GPD2, encoding a multidomain enzyme with a putative phosphoserine phosphatase (PSP) motif fused to glycerol‐3‐phosphate dehydrogenase (GPD) domains. Canonical GPD enzymes catalyze the synthesis of glycerol‐3‐phosphate (G3P) by reduction of dihydroxyacetone phosphate (DHAP). G3P forms the backbone of TAGs and membrane glycerolipids and it can be dephosphorylated to yield glycerol, an osmotic stabilizer and compatible solute under hypertonic stress. Recombinant Chlamydomonas GPD2 showed both reductase and phosphatase activities in vitro and it can work as a bifunctional enzyme capable of synthesizing glycerol directly from DHAP. In addition, GPD2 and a gene encoding glycerol kinase were up‐regulated in Chlamydomonas cells exposed to high salinity. RNA‐mediated silencing of GPD2 revealed that the multidomain enzyme was required for TAG accumulation under nitrogen deprivation and for glycerol synthesis under high salinity. Moreover, a GPD2‐mCherry fusion protein was found to localize to the chloroplast, supporting the existence of a GPD2‐dependent plastid pathway for the rapid synthesis of glycerol in response to hyperosmotic stress. We hypothesize that the reductase and phosphatase activities of PSP–GPD multidomain enzymes may be modulated by post‐translational modifications/mechanisms, allowing them to synthesize primarily G3P or glycerol depending on environmental conditions and/or metabolic demands in algal species of the core Chlorophytes.

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“…Other carbon metabolic genes that could be regulated by NsbHLH2 included PK, PPKD, and PEPCK, which are involved in the production of pyruvate, phosphoenolpyruvate, and OAA, respectively. Located at the metabolic hub of gluconeogenesis, glycolysis, and TCA cycle, these molecules and enzymes play important roles in carbon concentrating and partitioning depending on cellular needs (Johnson & Alric, ; Polle et al, ; Radakovits et al, ). We observed upregulation of PC , and downregulation of PK , PPDK , and PEPCK , which can result in the accumulation of OAA.…”

Section: Discussionmentioning

confidence: 99%

Increased biomass and lipid production by continuous cultivation of Nannochloropsis salina transformant overexpressing a bHLH transcription factor

Kang

Kim

Sung

et al. 2019

Biotech & Bioengineering

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Microalgae are promising feedstocks for sustainable and eco‐friendly production of biomaterials, which can be improved by genetic engineering. It is also necessary to optimize the processes to produce biomaterials from engineered microalgae. We previously reported that genetic improvements of an industrial microalga Nannochloropsis salina by overexpressing a basic helix‐loop‐helix transcription factor (NsbHLH2). These transformants showed an improved growth and lipid production particularly during the early phase of culture under batch culture. However, they had faster uptake of nutrients, resulting in earlier starvation and reduced growth during the later stages. We attempted to optimize the growth and lipid production by growing one of the transformants in continuous culture with variable dilution rate and feed nitrogen concentration. Relative to wild‐type, NsbHLH2 transformant consumed more nitrate at a high dilution rate (0.5 day −1 ), and had greater biomass production. Subsequently, nitrogen limitation at continuous cultivation led to an increased fatty acid methyl ester production by 83.6 mg l −1 day −1 . To elucidate genetic mechanisms, we identified the genes containing E‐boxes, known as binding sites for bHLH transcription factors. Among these, we selected 18 genes involved in the growth and lipid metabolism, and revealed their positive contribution to the phenotypes via quantitative real‐time polymerase chain reaction. These results provide proof‐of‐concept that NsbHLH2 can be used to produce biomass and lipids.

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Carbon Partitioning in Green Algae (Chlorophyta) and the Enolase Enzyme

Cited by 24 publications

References 67 publications

Real-time iTRAQ-based proteome profiling revealed the central metabolism involved in nitrogen starvation induced lipid accumulation in microalgae

Real-time iTRAQ-based proteome profiling revealed the central metabolism involved in nitrogen starvation induced lipid accumulation in microalgae

A multidomain enzyme, with glycerol‐3‐phosphate dehydrogenase and phosphatase activities, is involved in a chloroplastic pathway for glycerol synthesis in Chlamydomonas reinhardtii

Increased biomass and lipid production by continuous cultivation of Nannochloropsis salina transformant overexpressing a bHLH transcription factor

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