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Probing the biogenesis pathway and dynamics of thylakoid membranes_C4PR_LIV

ABSTRACT: Thylakoid membranes are the specialized internal membrane system produced in plants, algae, and cyanobacteria to convert sunlight to chemical energy via oxygenic photosynthesis. Cyanobacterial thylakoid membranes harbor the protein complexes and electron transport molecules that are necessary for photosynthetic light reactions and respiratory electron flow. The thylakoid membranes sit between the plasma membrane and the central cytoplasm, leading to intricate cellular compartmentalization. How thylakoid membranes are generated to form the functional network and how protein complexes are recruited into thylakoids remain elusive. Here, we developed a method to modulate thylakoid biogenesis in the model cyanobacterium Synechococcus elongatus PCC7942 and probed the spatial-temporal stepwise biogenesis process of cyanobacterial thylakoid membranes, using electron microscopy, in situ cryo-electron tomography, confocal microscopy, mass spectroscopy, and biochemical approaches. Our results revealed that the plasma membrane and regularly-arranged concentric thylakoid layers have no physical connections. The newly synthesized thylakoid membrane fragments commerce between the plasma membrane and pre-existing thylakoids, where the initial biogenesis of Photosystem II occurs. Photosystem I monomers appear in thylakoid membranes earlier than other photosystem assemblies. Redistribution of photosynthetic protein complexes during thylakoid biogenesis ensures establishment of the spatial organization of the functional thylakoid membrane network. This study provides insights into the molecular processes of the photosynthetic machinery biosynthesis and organization.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Synechococcus Elongatus (strain Pcc 7942) (anacystis Nidulans R2)

TISSUE(S): Bacterial Protein

DISEASE(S): Disease Free

SUBMITTER: Deborah Simpson

LAB HEAD: Professor Lu-Ning Liu

PROVIDER: PXD019731 | Pride | 2020-11-17

REPOSITORIES: Pride

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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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Probing the biogenesis pathway and dynamics of thylakoid membranes_C4PR_LIV

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