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Literature summary extracted from

  • Vidal-Meireles, A.; Neupert, J.; Zsigmond, L.; Rosado-Souza, L.; Kovacs, L.; Nagy, V.; Galambos, A.; Fernie, A.R.; Bock, R.; Toth, S.Z.
    Regulation of ascorbate biosynthesis in green algae has evolved to enable rapid stress-induced response via the VTC2 gene encoding GDP-L-galactose phosphorylase (2017), New Phytol., 214, 668-681 .
    View publication on PubMed

Cloned(Commentary)

EC Number Cloned (Comment) Organism
2.7.7.69 gene VTC2, quantitative RT-PCR enzyme expression analysis Chlamydomonas reinhardtii

Protein Variants

EC Number Protein Variants Comment Organism
2.7.7.69 additional information Chlamydomonas reinhardtii strain cw15-325 is used as recipient strain for transformation with VTC2 amiRNA. The VTC2 gene encoding GDP-L-galactose phosphorylase is targeted using artificial microRNAs. Upon H2O2 stress, alanine and proline accumulated, whereas the amount of cystine strongly decreases in the VTC2 amiRNA lines. The amounts of aspartic acid, lysine and ornithine are lower in the VTC2 amiRNA lines under control conditions, but these differences are much smaller following H2O2 stress. Changes in the tricarboxylic acid cycle intermediates are also apparent. Following H2O2 treatment, the amount of pyruvic acid and citric acid decreases, but the amounts of malic acid and succinic acid increases in all the lines. Furthermore, the amount of mannose and glycerol-3-phosphate decreases in the VTC2 amiRNA lines. Phenotype analysis, overview Chlamydomonas reinhardtii

Natural Substrates/ Products (Substrates)

EC Number Natural Substrates Organism Comment (Nat. Sub.) Natural Products Comment (Nat. Pro.) Rev. Reac.
2.7.7.69 GDP-alpha-D-glucose + alpha-D-mannose 1-phosphate Chlamydomonas reinhardtii
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 alpha-D-glucose 1-phosphate + GDP-alpha-D-mannose
-
 ?
2.7.7.69 GDP-alpha-D-glucose + alpha-D-mannose 1-phosphate Chlamydomonas reinhardtii cw15-325
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 alpha-D-glucose 1-phosphate + GDP-alpha-D-mannose
-
 ?
2.7.7.69 GDP-beta-L-galactose + alpha-D-mannose 1-phosphate Chlamydomonas reinhardtii
-
 beta-L-galactose 1-phosphate + GDP-alpha-D-mannose
-
 ?
2.7.7.69 GDP-beta-L-galactose + alpha-D-mannose 1-phosphate Chlamydomonas reinhardtii cw15-325
-
 beta-L-galactose 1-phosphate + GDP-alpha-D-mannose
-
 ?

Organism

EC Number Organism UniProt Comment Textmining
2.7.7.69 Chlamydomonas reinhardtii A0A2K3D0V9
-
-
2.7.7.69 Chlamydomonas reinhardtii cw15-325 A0A2K3D0V9
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-

Substrates and Products (Substrate)

EC Number Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
2.7.7.69 GDP-alpha-D-glucose + alpha-D-mannose 1-phosphate
-
 Chlamydomonas reinhardtii alpha-D-glucose 1-phosphate + GDP-alpha-D-mannose
-
 ?
2.7.7.69 GDP-alpha-D-glucose + alpha-D-mannose 1-phosphate
-
 Chlamydomonas reinhardtii cw15-325 alpha-D-glucose 1-phosphate + GDP-alpha-D-mannose
-
 ?
2.7.7.69 GDP-beta-L-galactose + alpha-D-mannose 1-phosphate
-
 Chlamydomonas reinhardtii beta-L-galactose 1-phosphate + GDP-alpha-D-mannose
-
 ?
2.7.7.69 GDP-beta-L-galactose + alpha-D-mannose 1-phosphate
-
 Chlamydomonas reinhardtii cw15-325 beta-L-galactose 1-phosphate + GDP-alpha-D-mannose
-
 ?

Synonyms

EC Number Synonyms Comment Organism
2.7.7.69 GDP-galactose:glucose-1-phosphate guanyltransferase UniProt Chlamydomonas reinhardtii
2.7.7.69 Vtc2
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 Chlamydomonas reinhardtii

Expression

EC Number Organism Comment Expression
2.7.7.69 Chlamydomonas reinhardtii expression of the VTC2 gene is rapidly induced by H2O2 and 1O2 resulting in a manifold increase in ascorbate content. The Chlamydomonas reinhardtii cell wall-deficient strain cw15-325 carrying a mutation in the argininosuccinate lyase (ARG7) with the VTC2-specific amiRNA vectors. In the case of the CDS-targeting amiRNA (VTC2-A) construct, 96 arginine-prototrophic colonies are tested by PCR and 89 of them are found to carry the whole amiRNA cassette. For the VTC2 3'-UTR-targeting amiRNA (VTC2-B) construct, 45 of the 96 tested arginine-prototrophic colonies carry the whole amiRNA cassette. Their Asc content shows a strong reduction (at least 80% reduction in 70% of the strains). In the VTC2 amiRNA lines, the mRNA abundances of APX1 and DHAR1, the main chloroplastic forms, are about 40% lower than in the EV2 control. The mutant lines also respond to high-light treatment up

General Information

EC Number General Information Comment Organism
2.7.7.69 malfunction the VTC2 amiRNA lines grow more slowly, have lower chlorophyll content, and are more susceptible to stress than the control strains. Ascorbate concentrations in VTC2 amiRNA lines are reduced to 10% of wild-type level. In the VTC2 amiRNA lines, the mRNA abundances of APX1 and DHAR1, the main chloroplastic forms, are about 40% lower than in the EV2 control Chlamydomonas reinhardtii
2.7.7.69 metabolism Chlamydomonas VTC2 lacks negative feedback regulation by ascorbate in the physiological concentration range. Ascorbate biosynthesis is also highly regulated in Chlamydomonas albeit via mechanisms distinct from those described in land plants. Dependence of Asc biosynthesis on the photosynthetic electron transport chain Chlamydomonas reinhardtii
2.7.7.69 physiological function GDP-L-galactose phosphorylase plays a pivotal role in ascorbate biosynthesis. In contrast to plants, there is no circadian regulation of ascorbate biosynthesis, photosynthesis is not required per se for ascorbate biosynthesis, and Chlamydomonas VTC2 lacks negative feedback regulation by ascorbate in the physiological concentration range Chlamydomonas reinhardtii