Expression of the minor isoform pea ferredoxin in tobacco alters photosynthetic electron partitioning and enhances cyclic electron flow

Ferredoxins (Fds) are ferrosulfoproteins that function as low-potential electron carriers in plants. The Fd family is composed of several isoforms that share high sequence homology but differ in functional characteristics. In leaves, at least two isoforms conduct linear and cyclic photosynthetic electron transport around photosystem I, and mounting evidence suggests the existence of at least partial division of duties between these isoforms. To evaluate the contribution of different kinds of Fds to the control of electron fluxes along the photosynthetic electron transport chain, we overexpressed a minor pea (Pisum sativum) Fd isoform (PsFd1) in tobacco (Nicotiana tabacum) plants. The transplastomic OeFd1 plants exhibited variegated leaves and retarded growth and developmental rates. Photosynthetic studies of these plants indicated a reduction in carbon dioxide assimilation rates, photosystem II photochemistry, and linear electron flow. However, the plants showed an increase in nonphotochemical quenching, better control of excitation pressure at photosystem II, and no evidence of photoinhibition, implying a better dynamic regulation to remove excess energy from the photosynthetic electron transport chain. Finally, analysis of P700 redox status during illumination confirmed that the minor pea Fd isoform promotes enhanced cyclic flow around photosystem I. The two novel features of this work are: (1) that Fd levels achieved in transplastomic plants promote an alternative electron partitioning even under greenhouse light growth conditions, a situation that is exacerbated at higher light intensity measurements; and (2) that an alternative, minor Fd isoform has been overexpressed in plants, giving new evidence of labor division among Fd isoforms.Fil: Blanco, Nicolás Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Biología Molecular y Celular de Rosario; Argentina. Universidad de Umea; SueciaFil: Ceccoli, Romina Denis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Dalla Via, Maria Virginia. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular; ArgentinaFil: Voss, Ingo. Universität Osnabrück; AlemaniaFil: Segretin, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones En Ingeniería Genética y Biología Molecular; ArgentinaFil: Bravo Almonacid, Fernando Felix. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones En Ingeniería Genética y Biología Molecular; ArgentinaFil: Melzer, Michael. Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung, Physiologie und Zellbiologie; AlemaniaFil: Hajirezaei, Mohammad Reza. Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung, Physiologie und Zellbiologie; ArgentinaFil: Scheibe, Renate. Universität Osnabrück; AlemaniaFil: Hanke, Guy T.. Universität Osnabrück; Alemani

Association of Ferredoxin:NADP+ oxidoreductase with the photosynthetic apparatus modulates electron transfer in Chlamydomonas reinhardtii

R.M. acknowledges support from the MEXT (Ministry of Education, Culture, Sports, Science and Technology, 15K21122). T.H. gratefully acknowledges support from the DFG (DIP project cooperation “Nanoengineered optoelectronics with biomaterials and bioinspired assemblies”) and the Volkswagen Foundation (LigH2t). G.K. acknowledges support from CREST, Japan Science and Technology Agency. M.H. acknowledges support from the DFG (Deutsche Forschungsgemeinschaft, HI 739/13-1)

Numerical approach to a model for quasistatic damage with spatial BV-regularization

We address a model for rate-independent, partial, isotropic damage in quasistatic small strain linear elasticity, featuring a damage variable with spatial BV-regularization. Discrete solutions are obtained using an alternate time-discrete scheme and the Variable-ADMM algorithm to solve the constrained nonsmooth optimization problem that determines the damage variable at each time step. We prove convergence of the method and show that discrete solutions approximate a semistable energetic solution of the rate-independent system. Moreover, we present our numerical results for two benchmark problems

GPVI and GPIbα Mediate Staphylococcal Superantigen-Like Protein 5 (SSL5) Induced Platelet Activation and Direct toward Glycans as Potential Inhibitors

Background Staphylococcus aureus (S. aureus) is a common pathogen capable of causing life-threatening infections. Staphylococcal superantigen-like protein 5 (SSL5) has recently been shown to bind to platelet glycoproteins and induce platelet activation. This study investigates further the interaction between SSL5 and platelet glycoproteins. Moreover, using a glycan discovery approach, we aim to identify potential glycans to therapeutically target this interaction and prevent SSL5-induced effects. Methodology/Principal Findings In addition to platelet activation experiments, flow cytometry, immunoprecipitation, surface plasmon resonance and a glycan binding array, were used to identify specific SSL5 binding regions and mediators. We independently confirm SSL5 to interact with platelets via GPIbα and identify the sulphated-tyrosine residues as an important region for SSL5 binding. We also identify the novel direct interaction between SSL5 and the platelet collagen receptor GPVI. Together, these receptors offer one mechanistic explanation for the unique functional influences SSL5 exerts on platelets. A role for specific families of platelet glycans in mediating SSL5-platelet interactions was also discovered and used to identify and demonstrate effectiveness of potential glycan based inhibitors in vitro. Conclusions/Significance These findings further elucidate the functional interactions between SSL5 and platelets, including the novel finding of a role for the GPVI receptor. We demonstrate efficacy of possible glycan-based approaches to inhibit the SSL5-induced platelet activation. Our data warrant further work to prove SSL5-platelet effects in viv

ROS production and signalling in chloroplasts:cornerstones and evolving concepts

Reactive oxygen species (ROS) such as singlet oxygen, superoxide (O(2) (●−)) and hydrogen peroxide (H(2)O(2)) are the markers of living cells. Oxygenic photosynthesis produces ROS in abundance, which act as a readout of a functional electron transport system and metabolism. The concept that photosynthetic ROS production is a major driving force in chloroplast to nucleus retrograde signalling is embedded in the literature, as is the role of chloroplasts as environmental sensors. The different complexes and components of the photosynthetic electron transport chain (PETC) regulate O(2) (●−) production in relation to light energy availability and the redox state of the stromal Cys‐based redox systems. All of the ROS generated in chloroplasts have the potential to act as signals and there are many sulphhydryl‐containing proteins and peptides in chloroplasts that have the potential to act as H(2)O(2) sensors and function in signal transduction. While ROS may directly move out of the chloroplasts to other cellular compartments, ROS signalling pathways can only be triggered if appropriate ROS‐sensing proteins are present at or near the site of ROS production. Chloroplast antioxidant systems serve either to propagate these signals or to remove excess ROS that cannot effectively be harnessed in signalling. The key challenge is to understand how regulated ROS delivery from the PETC to the Cys‐based redox machinery is organised to transmit redox signals from the environment to the nucleus. Redox changes associated with stromal carbohydrate metabolism also play a key role in chloroplast signalling pathways

Electron Transport in Cyanobacteria and Its Potential in Bioproduction

Cyanobacteria are the only prokaryotes capable of oxygenic photosynthesis. They play a key role in the environment and have enormous potential as a platform for renewable production of food, power, chemicals, and biofuels. Cyanobacteria incorporate a range of interlinked electron transport pathways with various roles in energy generation, photoprotection, and as a source of electrons and reducing power for a range of metabolic processes. In this review, we outline the components involved in linear and cyclic photosynthesis, and respiration, detail the processes by which electrons are transferred, and the energy outputs of each pathway. We also detail the components involved in photoprotection, carbon fixation, photorespiration, and electron export and the importance of these processes under different environmental conditions. A range of metabolic processes dependent on interactions with electron transport chain components are also outlined. We also discuss regulation of electron flux and the spatial organization of electron transport components, and the importance of these for optimal cellular growth. Finally, we discuss mechanisms by which electron transport pathways could be manipulated for biotechnology applications, including increased growth, electrical power generation, and hydrogen and industrial chemical production