On the use of oxygenic photosynthesis for the sustainable production of commodity chemicals

A sustainable society will have to largely refrain from the use of fossil carbon deposits. In such a regime, renewable electricity can be harvested as a primary source of energy. However, as for the synthesis of carbon‐based materials from bulk chemicals, an alternative is required. A sustainable approach towards this is the synthesis of commodity chemicals from CO₂, water and sunlight. Multiple paths to achieve this have been designed and tested in the domains of chemistry and biology. In the latter, the use of both chemotrophic and phototrophic organisms has been advocated. ‘Direct conversion’ of CO₂ and H₂O, catalyzed by an oxyphototroph, has excellent prospects to become the most economically competitive of these transformations, because of the relative ease of scale‐up of this process. Significantly, for a wide range of energy and commodity products, a proof of principle via engineering of the corresponding production organism has been provided. In the optimization of a cyanobacterial production organism, a wide range of aspects has to be addressed. Of these, here we will put our focus on: (1) optimizing the (carbon) flux to the desired product; (2) increasing the genetic stability of the producing organism and (3) maximizing its energy conversion efficiency. Significant advances have been made on all these three aspects during the past 2 years and these will be discussed: (1) increasing the carbon partitioning to >50%; (2) aligning product formation with the growth of the cells and (3) expanding the photosynthetically active radiation region for oxygenic photosynthesis.     

Towards a more accurate future for chlorophyll a and b determinations: the inaccuracies of Daniel Arnon’s assay

Photosynthesis Research - A recent publication (Esteban in New Phytol 217:341–342, 2018) describes how the use and citation of the assay of chlorophylls a and b extracted in aqueous 80%...     

Coupling physiological analysis with proteomic profile to understand the photosynthetic responses of young Euterpe oleracea palms to drought

Photosynthesis Research - This study examined whether drought sensitivity in açaí (Euterpe oleracea Mart.) is associated with reductions in photosynthesis and increasing oxidative stress...     

Redox-based control of the gamma heavy chain ATPase from Chlamydomonas outer arm dynein

The outer dynein arm from Chlamydomonas flagella contains two redox-active thioredoxin-related light chains associated with the alpha and beta heavy chains; these proteins belong to a distinct subgroup within the thioredoxin family. This observation suggested that some aspect of dynein activity might be modulated through redox poise. To test this, we have examined the effect of sulfhydryl oxidation on the ATPase activity of isolated dynein and axonemes from wildtype and mutant strains lacking various heavy chain combinations. The outer, but not inner, dynein arm ATPase was stimulated significantly following treatment with low concentrations of dithionitrobenzoic acid; this effect was readily reversible by dithiol, and to a lesser extent, monothiol reductants. Mutational and biochemical dissection of the outer arm revealed that ATPase activation in response to DTNB was an exclusive property of the gamma heavy chain, and that enzymatic enhancement was modulated by the presence of other dynein components. Furthermore, we demonstrate that the LC5 thioredoxin-like light chain binds to the N-terminal stem domain of the alpha heavy chain and that the beta heavy chain-associated LC3 protein also interacts with the gamma heavy chain. These data suggest the possibility of a dynein-associated redox cascade and further support the idea that the gamma heavy chain plays a key regulatory role within the outer arm.     

Ferrocene substituted thiacyclophanes: Synthesis, electrochemistry and structure of 6-ethynylferrocene-2,11-dithia[3.3]orthocyclophane

6-Ethynylferrocene-2,11-dithia[3.3]orthocyclophane has been prepared by cross-coupling 6-bromo-2,11-dithia[3.3]orthocyclophane to ethynylferrocene under Sonogashira conditions. The dynamic structure in solution of this potential ligand has been examined by variable temperature NMR whereas its solid state structure has been determined by X-ray diffraction studies. The electrochemical parameters of this cyclophane have also been examined.     

Lipid bodies in oxidized LDL-induced foam cells are leukotriene-synthesizing organelles: a MCP-1/CCL2 regulated phenomenon

Lipid-laden foam macrophages are emerging as key players in early atherogenesis. Even though cytoplasmic lipid bodies (lipid droplets) are now recognized as organelles with cell functions beyond lipid storage, the mechanisms controlling lipid body biogenesis within macrophages and their additional functions in atherosclerosis are not completely elucidated. Here we studied oxLDL-elicited macrophage machinery involved in lipid body biogenesis as well as lipid body roles in leukotriene (LT) synthesis. Both in vivo and in vitro, oxLDL (but not native LDL) induced rapid assembly of cytoplasmic lipid bodies-bearing ADRP within mice macrophages. Such oxLDL-elicited foamy-like phenotype was a pertussis toxin-sensitive process that depended on a paracrine activity of endogenous MCP-1/CCL2 and activation of ERK. Pretreatment with neutralizing anti-MCP-1/CCL2 inhibited macrophage ADRP protein expression induced by oxLDL. By directly immuno-localizing leukotrienes at their sites of synthesis, we showed that oxLDL-induced newly formed lipid bodies function as active sites of LTB₄ and LTC₄ synthesis, since oxLDL-induced lipid bodies within foam macrophages compartmentalized the enzyme 5-lipoxygenase and five lipoxygenase-activating protein (FLAP) as well as newly formed LTB₄ and LTC₄. Consistent with MCP-1/CCL-2 role in ox-LDL-induced lipid body biogenesis, in CCR2 deficient mice both ox-LDL-induced lipid body assembly and LT release were reduced as compared to wild type mice. In conclusion, oxLDL-driven foam cells are enriched with leukotriene-synthesizing lipid bodies – specialized organelles whose biogenic process is mediated by MCP-1/CCL2-triggered CCR2 activation and ERK-dependent downstream signaling – that may amplify inflammatory mediator production in atherosclerosis.     

High survival rate of a critically endangered species, the Azores Bullfinch Pyrrhula murina, as a contribution to population recovery

This paper reports analyses of a capture–mark–recapture (CMR) dataset of 149 Azores Bullfinches ringed on S?o Miguel island (Azores) between 2005 and 2007, and recaptured–resighted on a monthly basis over a 4-year period (2005–2008) throughout their breeding range. We examined the effect of time, age (adults vs. juveniles), gender (adult males and females), and environmental covariates (temperature, rainfall, NAO index) on survival probabilities. The modelling found a high and constant monthly survival probability (mean ± SE) estimated at 0.96 ± 0.01, similar between both adults and juveniles and independent of environmental conditions and gender. These findings agree with expectations from island-based life-history theory where relatively mild conditions and lack of predators should favour high survival rates to compensate for the low reproductive output. The annual survival rate was estimated at 0.62, which was also consistent with this pattern when compared with survival estimates of mainland bullfinch and passerine species on other subtropical islands obtained in similar CMR studies. Based on a canonical estimator, the size of the studied population (mean ± SE) was estimated at 1608 ± 326 individuals. Given that the population size was only around 120–400 individuals in the early 1990s, we suggest that the high survival probabilities currently applying to this critically endangered species may have substantially contributed to the recent recovery of this population. Future research studies on the species’ demography should continue to monitor survival in order to measure the effect of management interventions currently taking place within the range of the Azores Bullfinch, including the restoration of the biodiversity rich laurel forest, but also focusing on nest success, which is important for understanding population dynamics.     

Activity-independent prespecification of synaptic partners in the visual map of Drosophila

Specifying synaptic partners and regulating synaptic numbers are at least partly activity-dependent processes during visual map formation in all systems investigated to date . In Drosophila, six photoreceptors that view the same point in visual space have to be sorted into synaptic modules called cartridges in order to form a visuotopically correct map . Synapse numbers per photoreceptor terminal and cartridge are both precisely regulated . However, it is unknown whether an activity-dependent mechanism or a genetically encoded developmental program regulates synapse numbers. We performed a large-scale quantitative ultrastructural analysis of photoreceptor synapses in mutants affecting the generation of electrical potentials (norpA, trp;trpl), neurotransmitter release (hdc, syt), vesicle endocytosis (synj), the trafficking of specific guidance molecules during photoreceptor targeting (sec15), a specific guidance receptor required for visual map formation (Dlar), and 57 other novel synaptic mutants affecting 43 genes. Remarkably, in all these mutants, individual photoreceptors form the correct number of synapses per presynaptic terminal independently of cartridge composition. Hence, our data show that each photoreceptor forms a precise and constant number of afferent synapses independently of neuronal activity and partner accuracy. Our data suggest cell-autonomous control of synapse numbers as part of a developmental program of activity-independent steps that lead to a "hard-wired" visual map in the fly brain.