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The Conserved Small Protein SniP3 is Involved in Nitrogen Stress Response and Metabolic Regulation among Cyanobacteria

ABSTRACT: Cyanobacteria are oxygenic phototrophs that are regularly exposed to fluctuating environmental conditions. Particularly the availability of CO2 and combined nitrogen sources vary in many aquatic habitats. In the present study we investigated the role of SniP3, a well conserved, 3 kDa nitrogen starvation-induced protein, which is mainly localized on thylakoid membranes. Deletion of sniP3 resulted in a non-bleaching phenotype and reduced glycogen accumulation under N-limited conditions. Many more distinct metabolic alterations were observed, whereas the signaling molecule 2-oxoglutarate and the overall transcriptome remained comparable in mutant and wild-type cells under N-replete and N-deplete conditions. The SniP3 interactome revealed glyceraldehyde-3-phosphate dehydrogenase (Gap2) as main specific interaction partner. Gap2 activity was lowered in cells of the sniP3 mutant, while the activity of recombinant Gap2 was stimulated in the presence of the soluble N-terminal part of SniP3. Corresponding to the interaction of SniP3 and Gap2, the sniP3 mutant was unable to grow heterotrophically with glucose in the dark. Collectively, our result imply that the SniP3 protein plays an important role in the regulation of the cyanobacterial metabolism under fluctuation C/N conditions.

ORGANISM(S): Synechocystis sp. PCC 6803

PROVIDER: GSE309178 | GEO | 2025/12/15

REPOSITORIES: GEO

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Project description:The trophic condition related proteomes of an oxygenic photosynthetic cyanobacterium Synechocystis sp. PCC 6803 (glucose tolerant strain) were analyzed to get further insights into the metabolic traits governing the early exponential growth under photoautotrophic, mixotrophic and heterotrophic conditions. The cells were grown under constant light autotrophically (AT) in low (air-level) CO2 (ATLC) and in high CO2 (ATHC), mixotrophically (MT) in low (air-level) CO2 in the presence of glucose (MTLC) and heterotrophically in low (air-level) CO2 in the presence of glucose and only 10 min exposure to light every 24 hours (Light-Activated Heterotrophic Growth; LAHGLC). The proteomes of ATHC, MTLC and LAHGLC differed substantially from that of ATLC, particularly by downregulation of the inducible carbon concentrating mechanisms (CCM) and photorespiration related enzymes. On the contrary, under carbon-rich conditions (ATHC, MTLC, LAHGLC) the cells accumulated respiratory NAD(P)H dehydrogenase I complexes in the thylakoid membrane. In glucose supplemented cultures (MTLC, LAHGLC) a distinct NDH-2 protein, NdbA, additionally accumulated in the thylakoid membrane whilst the plasma membrane localized NdbC and ARTO decreased in abundance. The light-harvesting proteins together with the photosystem I and II subunits were uniquely depleted under LAHGLC condition, accumulated under ATHC and in MTLC remained at the level of the reference ATLC condition. The accumulation of P-transporters was unique, revealing only minor differences between ATLC and ATHC but strong up-regulation in MTLC and down-regulation in LAHGLC. This likely implies that MTLC stores energy surplus in the highly energetic bonds of polyphosphate polymer that can be used under unfavorable growth conditions. It is concluded that the rigor of cell growth in MTLC condition results to a great extent from high intracellular inorganic carbon conditions created upon glucose breakdown and release of CO2, beside the direct utilization of glucose-derived carbon skeletons for growth. This combination provides the MTLC cultures with excellent conditions for growth that often exceeds that of the mere photoautotrophic growth at high CO2.

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The Conserved Small Protein SniP3 is Involved in Nitrogen Stress Response and Metabolic Regulation among Cyanobacteria

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