Modulation of the major paths of XXXX in photorespiratory mutants of @entity324 .

@entity7955 @entity25104 @entity2228 @entity1792 @entity7352 @entity5910 @entity41202 @entity515 @entity5993 @entity969 @entity492 @entity324 @entity505 @entity3776
BACKGROUND: Recent studies using transcript and metabolite profiles of wild-type and gene deletion mutants revealed that photorespiratory pathways are essential for the growth of @entity324 under atmospheric conditions. Pool size changes of primary metabolites, such as @entity2228 and @entity25104 , indicated a link to photorespiration. METHODOLOGY/PRINCIPAL FINDINGS: The @entity7352 labelling kinetics of primary metabolites were analysed in photoautotrophically grown cultures of @entity324 by gas chromatography-mass spectrometry (GC-MS) to demonstrate the link with photorespiration. Cells pre-acclimated to high @entity515 (5%, HC) or limited @entity515 (0.035%, LC) conditions were pulse-labelled under very high (2% w/w) @entity7352 - @entity5993 (VHC) conditions followed by treatment with ambient @entity41202 at HC and LC conditions, respectively. The @entity7352 enrichment, relative changes in pool size, and @entity7352 flux of selected metabolites were evaluated. We demonstrate two major paths of @entity515 assimilation via Rubisco in @entity324 , i.e., from 3PGA via @entity7955 to @entity492 , @entity5910 and @entity1792 or, to a lesser extent, from 3PGA via @entity3776 to @entity969 . The results reveal evidence of @entity505 channelling from 3PGA to the PEP pool. Furthermore, @entity7352 labelling of glycolate was observed under conditions thought to suppress photorespiration. Using the glycolate-accumulating /\glcD1 mutant, we demonstrate enhanced @entity7352 partitioning into the glycolate pool under conditions favouring photorespiration and enhanced @entity7352 partitioning into the @entity2228 pool of the @entity2228 -accumulating /\gcvT mutant. Under LC conditions, the photorespiratory mutants /\glcD1 and /\gcvT showed enhanced activity of the additional @entity505 -fixing PEP carboxylase pathway. CONCLUSIONS/SIGNIFICANCE: With our approach of non-steady-state @entity7352 labelling and analysis of metabolite pool sizes with respective @entity7352 enrichments, we identify the use and modulation of major pathways of @entity505 assimilation in @entity324 in the presence of high and low inorganic @entity505 supplies.
