The Glycine Decarboxylase Complex is not Essential for the Cyanobacterium Synechocystis sp. Strain PCC 6803

Abstract

In order to investigate the metabolic importance of glycine decarboxylase (GDC) in cyanobacteria, mutants were generated defective in the genes encoding GDC subunits and the serine hydroxymethyl-transferase (SHMT). It was possible to mutate the genes for GDC subunits P, T, or H protein in the cyanobacterial model strain Synechocystis sp. PCC 6803, indicating that GDC is not necessary for cell viability under standard conditions. In contrast, the SHMT coding gene was found to be essential. Almost no changes in growth, pigmentation, or photosynthesis were detected in the GDC subunit mutants, regardless of whether or not they were cultivated at ambient or high CO2 concentrations. The mutation of GDC led to an increased glycine/serine ratio in the mutant cells. Furthermore, supplementation of the medium with low glycine concentrations was toxic for the mutants but not for wild type cells. Conditions stimulating photorespiration in plants, such as low CO2 concentrations, did not induce but decrease the expression of the GDC and SHMT genes in Synechocystis. It appears that, in contrast to heterotrophic bacteria and plants, GDC is dispensable for Synechocystis and possibly other cyanobacteria.

Metabolome Phenotyping of Inorganic Carbon Limitation in Cells of the Wild Type and Photorespiratory Mutants of the CyanobacteriumSynechocystissp. Strain PCC 6803

“…5). Indeed, high Gly was observed in mutant DgcvT in accordance with its genetic defect in the T-protein subunit of Gly decarboxylase (Hagemann et al, 2005). As indicated by above ICA, the difference of Gly levels compared to wild-type cells was moderate under HC conditions but became a dominant feature under LC conditions (Fig.…”

“…The generation and characterization of the mutants DglcD, bearing a defect in the GlcD coding gene sll0404, and DgcvT, bearing a defect in gene sll0171 coding for the T-protein subunit of the Gly decarboxylase complex, have been described elsewhere (Hagemann et al, 2005;Eisenhut et al, 2006). For all experiments, axenic cultures of the cyanobacteria were grown photoautotrophically in batch cultures using 3-cm glass vessels with 5-mm glass tubes for aeration (bubbling flow rate was 5 mL min 21 ) and 29°C growth temperature under continuous illumination of 130 mmol photons s 21 m…”

“…For this reason, free amino acids were extracted from frozen cyanobacterial cell pellets with 80% ethanol at 65°C for 3 h. After centrifugation, the supernatants were dried by lyophilization and redissolved in 8 mM Na 2 HPO 4 , pH 6.8, containing 2.5% tetrahydrofurane. Individual amino acids were assayed after derivatization with o-phthaldialdehyde and analyzed by HPLC as described by Hagemann et al (2005).…”

Regulation of Plant Glycine Decarboxylase byS-Nitrosylation and Glutathionylation

“…Samples were incubated for 30 min and then diluted 1:50 with the same phosphate buffer. Individual amino acids were separated by HPLC and quantified as described (Hagemann et al, 2005).…”

d-GLYCERATE 3-KINASE, the Last Unknown Enzyme in the Photorespiratory Cycle in Arabidopsis, Belongs to a Novel Kinase Family

“…Therefore, green algal GLYK is probably involved in photosynthetic-photorespiratory processes similar to land plants. By contrast, the complete knockout of Gly decarboxylase (which is an indispensable C 2 cycle enzyme in higher plants) does not impair the performance of Synochocystis to any measurable extent (Hagemann et al, 2005), suggesting that the C 2 cycle is of minor importance in this species and perhaps most cyanobacteria. Correspondingly, the Synechocystis genome does not harbor a plant-type GLYK gene, which seems to be restricted to complex cyanobacteria with larger genomes.…”