scholarly journals Carbohydrate Metabolism in Mutants of the Cyanobacterium Synechococcus elongatus PCC 7942 Defective in Glycogen Synthesis

2010 ◽  
Vol 76 (10) ◽  
pp. 3153-3159 ◽  
Author(s):  
Eiji Suzuki ◽  
Hajime Ohkawa ◽  
Katsuya Moriya ◽  
Tatsuya Matsubara ◽  
Yukari Nagaike ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Carbohydrate Metabolism ◽  
Glycogen Synthase ◽  
Glycogen Synthesis ◽  
Synechococcus Elongatus ◽  
Wild Type ◽  
Liquid Cultures ◽  
Marginal Effects ◽  
Synechococcus Elongatus Pcc 7942 ◽  
Pcc 7942

ABSTRACT ADP-glucose pyrophosphorylase (AGPase) and glycogen synthase (GS) catalyze the first two reactions of glycogen synthesis in cyanobacteria. Mutants defective in each of these enzymes in Synechococcus elongatus PCC 7942 were constructed and characterized. Activities of the corresponding enzymes in the selected mutants were virtually undetectable, and their ability to synthesize glycogen was entirely abolished. The maximal activities of photosynthetic O2 evolution and the rates of respiration in the dark were significantly decreased in the mutants compared to those in wild-type cells. Addition of 0.2 M NaCl or 3 mM H2O2 to liquid cultures markedly inhibited the growth of the AGPase and GS mutants, while the same treatment had only marginal effects on the wild type. These results suggest a significant role for storage polysaccharides in tolerance to salt or oxidative stress.

scholarly journals Mutations at pipX Suppress Lethality of PII-Deficient Mutants of Synechococcus elongatus PCC 7942

2009 ◽  
Vol 191 (15) ◽  
pp. 4863-4869 ◽  
Author(s):  
Javier Espinosa ◽  
Miguel Angel Castells ◽  
Karim Boumediene Laichoubi ◽  
Asunción Contreras
Keyword(s):  
Molecular Basis ◽  
Synechococcus Elongatus ◽  
Wild Type ◽  
Growth Defects ◽  
Genetic Inactivation ◽  
Domains Of Life ◽  
Synechococcus Elongatus Pcc 7942 ◽  
Pcc 7942 ◽  
Severe Growth ◽  
Null Mutants

ABSTRACT The PII proteins are found in all three domains of life as key integrators of signals reflecting the balance of nitrogen and carbon. Genetic inactivation of PII proteins is typically associated with severe growth defects or death. However, the molecular basis of these defects depends on the specific functions of the proteins with which PII proteins interact to regulate nitrogen metabolism in different organisms. In Synechococcus elongatus PCC 7942, where PII forms complexes with the NtcA coactivator PipX, attempts to engineer PII-deficient strains failed in a wild-type background but were successful in pipX null mutants. Consistent with the idea that PII is essential to counteract the activity of PipX, four different spontaneous mutations in the pipX gene were found in cultures in which glnB had been genetically inactivated.

scholarly journals Alanine Dehydrogenase Activity Is Required for Adequate Progression of Phycobilisome Degradation during Nitrogen Starvation in Synechococcus elongatus PCC 7942

2006 ◽  
Vol 188 (14) ◽  
pp. 5258-5265 ◽  
Author(s):  
Roxane Lahmi ◽  
Eleonora Sendersky ◽  
Alexander Perelman ◽  
Martin Hagemann ◽  
Karl Forchhammer ◽  
...  
Keyword(s):  
Dehydrogenase Activity ◽  
Cellular Response ◽  
Nitrogen Starvation ◽  
Synechococcus Elongatus ◽  
Wild Type ◽  
Sulfur Starvation ◽  
Alanine Dehydrogenase ◽  
In The Wild ◽  
Synechococcus Elongatus Pcc 7942 ◽  
Pcc 7942

ABSTRACT Degradation of the cyanobacterial light-harvesting antenna, the phycobilisome, is a general acclimation response that is observed under various stress conditions. In this study we identified a novel mutant of Synechococcus elongatus PCC 7942 that exhibits impaired phycobilisome degradation specifically during nitrogen starvation, unlike previously described mutants, which exhibit aberrant degradation under nitrogen, sulfur, and phosphorus starvation conditions. The phenotype of the new mutant, AldΩ, results from inactivation of ald (encoding alanine dehydrogenase). AldΩ is deficient in transcription induction of a number of genes during nitrogen starvation. These genes include the “general nutrient stress-related” genes, nblA and nblC, the products of which are essential for phycobilisome degradation. Furthermore, transcripts of several specific nitrogen-responsive genes accumulate at lower levels in AldΩ than in the wild-type strain. In contrast, ald inactivation did not decrease the accumulation of transcripts during sulfur starvation. Transcription of ald is induced upon nitrogen starvation, which is consistent with the ability of wild-type cells to maintain a low cellular content of alanine under these conditions. Unlike wild-type cells, AldΩ accumulates alanine upon nitrogen starvation. Our analyses suggest that alanine dehydrogenase activity is necessary for an adequate cellular response to nitrogen starvation. Decomposition of alanine may be required to provide a sufficient amount of ammonia. Furthermore, the accumulated alanine, or a related metabolite, may interfere with the cues that modulate acclimation during nitrogen starvation. Taken together, our results provide novel information regarding cellular responses to nitrogen starvation and suggest that mechanisms related to nitrogen-specific responses are involved in modulation of a general acclimation process.

Glycogen synthesis is a required component of the nitrogen stress response in Synechococcus elongatus PCC 7942

2013 ◽  
Vol 2 (2) ◽  
pp. 98-106 ◽  
Author(s):  
Jason W. Hickman ◽  
Kimberly M. Kotovic ◽  
Cameron Miller ◽  
Paul Warrener ◽  
Brett Kaiser ◽  
...  
Keyword(s):  
Stress Response ◽  
Glycogen Synthesis ◽  
Synechococcus Elongatus ◽  
Nitrogen Stress ◽  
Synechococcus Elongatus Pcc 7942 ◽  
Pcc 7942

scholarly journals Effects of Reduced and Enhanced Glycogen Pools on Salt-Induced Sucrose Production in a Sucrose-Secreting Strain of Synechococcus elongatus PCC 7942

2017 ◽  
Vol 84 (2) ◽  
Author(s):  
Cuncun Qiao ◽  
Yangkai Duan ◽  
Mingyi Zhang ◽  
Martin Hagemann ◽  
Quan Luo ◽  
...  
Keyword(s):  
Carbon Flux ◽  
Glycogen Synthesis ◽  
Sucrose Phosphate Synthase ◽  
Synechococcus Elongatus ◽  
Carbon Pool ◽  
Sucrose Synthesis ◽  
Content Type ◽  
Stressed Cells ◽  
Synechococcus Elongatus Pcc 7942 ◽  
Pcc 7942

ABSTRACT Sucrose and glycogen syntheses in cyanobacteria share the common precursor glucose-1-phosphate. It is generally assumed that lowering glycogen synthesis could drive more carbon toward sucrose synthesis that can be induced by salt stress among cyanobacteria. By using a theophylline-dependent riboswitch system, the expression of glgC, a key gene in glycogen synthesis, was downregulated in a quantitative manner in a sucrose-secreting strain of Synechococcus elongatus PCC 7942. We observed that the stepwise suppression of glycogen synthesis limited rather than stimulated sucrose production in the salt-stressed cells, suggesting that glycogen could serve as a carbon pool for the synthesis of sucrose. Accordingly, we generated glycogen-overproducing strains, but the increased glycogen pool alone did not stimulate sucrose production, indicating that alternative steps limit the carbon flux toward the synthesis of sucrose. Consistent with previous studies that showed that sucrose-phosphate synthase (SPS) catalyzes the rate-limiting step in sucrose synthesis, the combination of glycogen overproduction and sps overexpression resulted in increased sucrose production. Our results indicate that the glycogen and sucrose pools are closely linked in Synechococcus elongatus PCC 7942, and we propose that enhancing the glycogen pool could be a promising strategy for the improvement of sucrose production by cyanobacteria in the presence of a strong sucrose synthesis sink. IMPORTANCE Many cyanobacteria naturally synthesize and accumulate sucrose when stressed by NaCl, which provides novel possibilities for obtaining sugar feedstock by engineering of cyanobacteria. It has been assumed that glycogen synthesis competes with sucrose synthesis for the carbon flux. However, our results showed that the suppression of glycogen synthesis decreased rather than stimulated sucrose production in a sucrose-secreting strain of Synechococcus elongatus PCC 7942. This result suggests that glycogen could serve as a supportive rather than a competitive carbon pool for the synthesis of sucrose, providing new insights about the relation between glycogen synthesis and sucrose synthesis in cyanobacteria. This finding is also useful to guide metabolic engineering work to optimize the production of sucrose and possibly other products by cyanobacteria.

scholarly journals Photophysiological and Photosynthetic Complex Changes during Iron Starvation in Synechocystis sp. PCC 6803 and Synechococcus elongatus PCC 7942

PLoS ONE ◽  
2013 ◽  
Vol 8 (3) ◽  
pp. e59861 ◽  
Author(s):  
Jared M. Fraser ◽  
Sarah E. Tulk ◽  
Jennifer A. Jeans ◽  
Douglas A. Campbell ◽  
Thomas S. Bibby ◽  
...  
Keyword(s):  
Synechococcus Elongatus ◽  
Iron Starvation ◽  
Synechococcus Elongatus Pcc 7942 ◽  
Pcc 7942 ◽  
Synechocystis Sp ◽  
Pcc 6803
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