Differential FeS cluster photodamage plays a critical role in regulating excess electron flow through photosystem I.

The photosynthetic electron flux from photosystem I (PSI) is mainly directed to NADP and CO fixation, but a fraction is always shared between alternative and cyclic electron transport. Although the electron transfer from P700 to ferredoxin, via phylloquinone and the FeS, FeS and FeS clusters, is well characterized, the regulatory role of these redox intermediates in the delivery of electrons from PSI to NADP, alternative and cyclic electron transport under environmental stress remains elusive. Here we provide evidence for sequential damage to PSI FeS clusters under high light and subsequent slow recovery under low light in Arabidopsis thaliana.

Interplay between photosynthetic electron flux and organic carbon sinks in sucrose-excreting Synechocystis sp. PCC 6803 revealed by omics approaches.

Background: Advancing the engineering of photosynthesis-based prokaryotic cell factories is important for sustainable chemical production and requires a deep understanding of the interplay between bioenergetic and metabolic pathways. Rearrangements in photosynthetic electron flow to increase the efficient use of the light energy for carbon fixation must be balanced with a strong carbon sink to avoid photoinhibition. In the cyanobacterium Synechocystis sp.

Accounting for photosystem I photoinhibition sheds new light on seasonal acclimation strategies of boreal conifers.

The photosynthetic acclimation of boreal evergreen conifers is controlled by regulatory and photoprotective mechanisms that allow conifers to cope with extreme environmental changes. However, the underlying dynamics of photosystem II (PSII) and photosystem I (PSI) remain unresolved. Here, we investigated the dynamics of PSII and PSI during the spring recovery of photosynthesis in Pinus sylvestris and Picea abies using a combination of chlorophyll a fluorescence, P700 difference absorbance measurements, and quantification of key thylakoid protein abundances.

PSI Photoinhibition and Changing CO Levels Initiate Retrograde Signals to Modify Nuclear Gene Expression.

Photosystem I (PSI) is a critical component of the photosynthetic machinery in plants. Under conditions of environmental stress, PSI becomes photoinhibited, leading to a redox imbalance in the chloroplast. PSI photoinhibition is caused by an increase in electron pressure within PSI, which damages the iron-sulfur clusters.

Photosynthetic and transcriptome responses to fluctuating light in ion transport triple mutant.

Fluctuating light intensity challenges fluent photosynthetic electron transport in plants, inducing photoprotection while diminishing carbon assimilation and growth, and also influencing photosynthetic signaling for regulation of gene expression. Here, we employed in vivo chlorophyll- fluorescence and P700 difference absorption measurements to demonstrate the enhancement of photoprotective energy dissipation of both photosystems in wild-type after 6 h exposure to fluctuating light as compared with constant light conditions. This acclimation response to fluctuating light was hampered in a triple mutant lacking the thylakoid ion transport proteins KEA3, VCCN1, and CLCe, leading to photoinhibition of photosystem I.

Enhanced function of non-photoinhibited photosystem II complexes upon PSII photoinhibition.

Light induced photosystem (PS)II photoinhibition inactivates and irreversibly damages the reaction center protein(s) but the light harvesting complexes continue the collection of light energy. Here we addressed the consequences of such a situation on thylakoid light harvesting and electron transfer reactions. For this purpose, Arabidopsis thaliana leaves were subjected to investigation of the function and regulation of the photosynthetic machinery after a distinct portion of PSII centers had experienced photoinhibition in the presence and absence of Lincomycin (Lin), a commonly used agent to block the repair of damaged PSII centers.

The Arabidopsis thylakoid chloride channel ClCe regulates ATP availability for light-harvesting complex II protein phosphorylation.

Coping with changes in light intensity is challenging for plants, but well-designed mechanisms allow them to acclimate to most unpredicted situations. The thylakoid K/H antiporter KEA3 and the voltage-dependent Cl channel VCCN1 play important roles in light acclimation by fine-tuning electron transport and photoprotection. Good evidence exists that the thylakoid Cl channel ClCe is involved in the regulation of photosynthesis and state transitions in conditions of low light.

Flv3A facilitates O photoreduction and affects H photoproduction independently of Flv1A in diazotrophic Anabaena filaments.

The model heterocyst-forming filamentous cyanobacterium Anabaena sp. PCC 7120 (Anabaena) is a typical example of a multicellular organism capable of simultaneously performing oxygenic photosynthesis in vegetative cells and O -sensitive N -fixation inside heterocysts. The flavodiiron proteins have been shown to participate in photoprotection of photosynthesis by driving excess electrons to O (a Mehler-like reaction).

Plants acclimate to Photosystem I photoinhibition by readjusting the photosynthetic machinery.

Photosynthetic light reactions require strict regulation under dynamic environmental conditions. Still, depending on environmental constraints, photoinhibition of Photosystem (PSII) or PSI occurs frequently. Repair of photodamaged PSI, in sharp contrast to that of PSII, is extremely slow and leads to a functional imbalance between the photosystems.

Gene expression and organization of thylakoid protein complexes in the PSII-less mutant of sp. PCC 6803.

Photosystems I and II (PSI and PSII) are the integral components of the photosynthetic electron transport chain that utilize light to provide chemical energy for CO fixation. In this study, we investigated how the deficiency of PSII affects the gene expression, accumulation, and organization of thylakoid protein complexes as well as physiological characteristics of sp. PCC 6803 by combining biochemical, biophysical, and transcriptomic approaches.

Role of serine/threonine protein kinase STN7 in the formation of two distinct photosystem I supercomplexes in Physcomitrium patens.

Reversible thylakoid protein phosphorylation provides most flowering plants with dynamic acclimation to short-term changes in environmental light conditions. Here, through generating Serine/Threonine protein kinase 7 (STN7)-depleted mutants in the moss Physcomitrella (Physcomitrium patens), we identified phosphorylation targets of STN7 kinase and their roles in short- and long-term acclimation of the moss to changing light conditions. Biochemical and mass spectrometry analyses revealed STN7-dependent phosphorylation of N-terminal Thr in specific Light-Harvesting Complex II (LHCII) trimer subunits (LHCBM2 and LHCBM4/8) and provided evidence that phospho-LHCBM accumulation is responsible for the assembly of two distinct Photosystem I (PSI) supercomplexes (SCs), both of which are largely absent in STN7-depleted mutants.

Patterning of the Autotrophic, Mixotrophic, and Heterotrophic Proteomes of Oxygen-Evolving Cyanobacterium sp. PCC 6803.

Proteomes of an oxygenic photosynthetic cyanobacterium, sp. PCC 6803, were analyzed under photoautotrophic (low and high CO, assigned as ATLC and ATHC), photomixotrophic (MT), and light-activated heterotrophic (LAH) conditions. Allocation of proteome mass fraction to seven sub-proteomes and differential expression of individual proteins were analyzed, paying particular attention to photosynthesis and carbon metabolism-centered sub-proteomes affected by the quality and quantity of the carbon source and light regime upon growth.

A kaleidoscope of photosynthetic antenna proteins and their emerging roles.

Photosynthetic light-harvesting antennae are pigment-binding proteins that perform one of the most fundamental tasks on Earth, capturing light and transferring energy that enables life in our biosphere. Adaptation to different light environments led to the evolution of an astonishing diversity of light-harvesting systems. At the same time, several strategies have been developed to optimize the light energy input into photosynthetic membranes in response to fluctuating conditions.

True oxygen reduction capacity during photosynthetic electron transfer in thylakoids and intact leaves.

Reactive oxygen species (ROS) are generated in electron transport processes of living organisms in oxygenic environments. Chloroplasts are plant bioenergetics hubs where imbalances between photosynthetic inputs and outputs drive ROS generation upon changing environmental conditions. Plants have harnessed various site-specific thylakoid membrane ROS products into environmental sensory signals.

Photosystem I Inhibition, Protection and Signalling: Knowns and Unknowns.

Photosynthesis is the process that harnesses, converts and stores light energy in the form of chemical energy in bonds of organic compounds. Oxygenic photosynthetic organisms (i.e.

Hydrocarbon Desaturation in Cyanobacterial Thylakoid Membranes Is Linked With Acclimation to Suboptimal Growth Temperatures.

The ability to produce medium chain length aliphatic hydrocarbons is strictly conserved in all photosynthetic cyanobacteria, but the molecular function and biological significance of these compounds still remain poorly understood. This study gives a detailed view to the changes in intracellular hydrocarbon chain saturation in response to different growth temperatures and osmotic stress, and the associated physiological effects in the model cyanobacterium sp. PCC 6803.

Characterization of the Free and Membrane-Associated Fractions of the Thylakoid Lumen Proteome in .

The thylakoid lumen houses proteins that are vital for photosynthetic electron transport, including water-splitting at photosystem (PS) II and shuttling of electrons from cytochrome to PSI. Other lumen proteins maintain photosynthetic activity through biogenesis and turnover of PSII complexes. Although all lumen proteins are soluble, these known details have highlighted interactions of some lumen proteins with thylakoid membranes or thylakoid-intrinsic proteins.

Comparison of alternative integration sites in the chromosome and the native plasmids of the cyanobacterium Synechocystis sp. PCC 6803 in respect to expression efficiency and copy number.

Background: Synechocystis sp. PCC 6803 provides a well-established reference point to cyanobacterial metabolic engineering as part of basic photosynthesis research, as well as in the development of next-generation biotechnological production systems. This study focused on expanding the current knowledge on genomic integration of expression constructs in Synechocystis, targeting a range of novel sites in the chromosome and in the native plasmids, together with established loci used in literature.

Global proteomic response of unicellular cyanobacterium Synechocystis sp. PCC 6803 to fluctuating light upon CO step-down.

Photosynthetic cyanobacteria are exposed to rapid changes in light intensity in their natural habitats, as well as in photobioreactors. To understand the effects of such fluctuations on Synechocystis sp. PCC 6803, the global proteome of cells grown under a fluctuating light condition (low background light interrupted with high light pulses) was compared to the proteome of cells grown under constant light with concomitant acclimation of cells to low CO level.

Rapid Transcriptional Reprogramming Triggered by Alteration of the Carbon/Nitrogen Balance Has an Impact on Energy Metabolism in sp. PCC 7120.

() sp. PCC 7120 is a filamentous cyanobacterial species that fixes N to nitrogenous compounds using specialised heterocyst cells. Changes in the intracellular ratio of carbon to nitrogen (C/N balance) is known to trigger major transcriptional reprogramming of the cell, including initiating the differentiation of vegetative cells to heterocysts.

PSB33 protein sustains photosystem II in plant chloroplasts under UV-A light.

Plants can quickly and dynamically respond to spectral and intensity variations of the incident light. These responses include activation of developmental processes, morphological changes, and photosynthetic acclimation that ensure optimal energy conversion and minimal photoinhibition. Plant adaptation and acclimation to environmental changes have been extensively studied, but many details surrounding these processes remain elusive.

Gel-based proteomic map of Arabidopsis thaliana root plastids and mitochondria.

Background: Non-photosynthetic plastids of plants are known to be involved in a range of metabolic and biosynthetic reactions, even if they have been difficult to study due to their small size and lack of color. The morphology of root plastids is heterogeneous and also the plastid size, density and subcellular distribution varies depending on the cell type and developmental stage, and therefore the functional features have remained obscure. Although the root plastid proteome is likely to reveal specific functional features, Arabidopsis thaliana root plastid proteome has not been studied to date.