2001
DOI: 10.1094/mpmi.2001.14.6.811
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The Disruption of a Gene Encoding a Putative Arylesterase Impairs Pyruvate Dehydrogenase Complex Activity and Nitrogen Fixation in Sinorhizobium meliloti

Abstract: Nitrogen-fixing Sinorhizobium meliloti cells depend upon dicarboxylic acids as carbon and energy sources. The metabolism of these intermediate compounds of the trichloroacetic acid cycle is dependent upon the availability of acetyl-coenzyme A (CoA). In bacteroids, the combined activities of malic enzymes and pyruvate dehydrogenase (PDH) have been proposed to be responsible for the anaplerotic synthesis of acetyl-CoA. We obtained a S. meliloti mutant strain, PD3, in which a Tn5 insertion led to a significant de… Show more

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Cited by 4 publications
(4 citation statements)
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“…This result is qualitatively in agreement with the fact that icd mutants on S. meliloti are symbiotically ineffective [28]. Similarly, constraint-based modeling concludes that a reduction of enzymatic activity in pyruvate dehydrogenase (PDH) induces a significant reduction in symbiotic nitrogen fixation but does not impair it as occurs in the case of S. meliloti bacteroids [29], see Figure 3 (B). This finding suggests that the role of PDH in the production of acetyl-coenzyme A can be replaced by alternative pathways in R. etli bacteroids [5].…”
Section: Discussionsupporting
confidence: 80%
“…This result is qualitatively in agreement with the fact that icd mutants on S. meliloti are symbiotically ineffective [28]. Similarly, constraint-based modeling concludes that a reduction of enzymatic activity in pyruvate dehydrogenase (PDH) induces a significant reduction in symbiotic nitrogen fixation but does not impair it as occurs in the case of S. meliloti bacteroids [29], see Figure 3 (B). This finding suggests that the role of PDH in the production of acetyl-coenzyme A can be replaced by alternative pathways in R. etli bacteroids [5].…”
Section: Discussionsupporting
confidence: 80%
“…The genes encoding the pyruvate dehydrogenase complex (pdhABC) are cotranscribed elsewhere on the chromosome (Cabanes et al 2000). Although dihydrolipoyl dehydrogenase can be shared between the pyruvate dehydrogenase and ␣-ketoglutarate dehydrogenase complexes (Mattevi et al 1992), a second dihydrolipoyl dehydrogenase (lpdA1) is encoded near pdhABC, and a mutation that was polar on its transcription abolished pyruvate dehydrogenase activity (Soto et al 2001).…”
Section: Tricarboxylic Acid Cyclementioning
confidence: 99%
“…Pyruvate dehydrogenase is a multienzyme complex encoded by two genes, pdhAa and pdhAb, in S. meliloti (Cabanes et al, 2000). Mutation of a putative arylesterase (ada), that clusters with the genes for pyruvate dehydrogenase, reduced the activity of pyruvate dehydrogenase in S. meliloti 16-fold and resulted in a Fix 2 phenotype (Soto et al, 2001). In rhizobia there are two forms of malic enzyme: an NADP 1 -dependant malic enzyme with high affinity that is stimulated by ammonium, and an NAD 1 -dependant malic enzyme with a lower affinity that is stimulated by potassium and ammonium salts (Finan et al, 1991;Driscoll and Finan, 1993;Driscoll and Finan, 1996).…”
Section: Nitrogen Fixation and Bacteroid Metabolism Of Dicarboxylatesmentioning
confidence: 99%