Evolutionary divergence of anaphase spindle mechanics in nematode embryos constrained by antagonistic pulling and viscous forces

Cellular functions such as cell division are remarkably conserved across phyla. However, the evolutionary principles of cellular organization that drive them are less well explored. Thus, an essential question remains: to what extent do cellular parameters evolve without altering the basic functions they sustain? Here we have observed six different nematode species for which the mitotic spindle is positioned asymmetrically during the first embryonic division. Whereas the C. elegans spindle undergoes oscillations during its displacement, the spindle elongates without oscillations in other species. We asked which evolutionary changes in biophysical parameters could explain differences in spindle motion while maintaining a constant output. Using laser microsurgery of the spindle, we revealed that all species are subjected to cortical pulling forces of varying magnitudes. Using a viscoelastic model to fit the recoil trajectories and with an independent measurement of cytoplasmic viscosity, we extracted the values of cytoplasmic drag, cortical pulling forces, and spindle elasticity for all species. We found large variations in cytoplasmic viscosity, whereas cortical pulling forces and elasticity were often more constrained. In agreement with previous simulations, we found that increased viscosity correlates with decreased oscillation speeds across species. However, the absence of oscillations in some species despite low viscosity can only be explained by smaller pulling forces. Consequently, we find that spindle mobility across the species analyzed here is characterized by a tradeoff between cytoplasmic viscosity and pulling forces normalized by the size of the embryo. Our work provides a framework for understanding mechanical constraints on evolutionary diversification of spindle mobility.     

Functional and phylogenetic diversity of an agricultural matrix avifauna: The role of habitat heterogeneity in Afrotropical farmland

Varied strategies to alleviate the loss of farmland biodiversity have been tested, yet there is still insufficient evidence supporting their effectiveness, especially when considering phylogenetic and functional diversity alongside traditional taxonomic diversity metrics. This conservation challenge is accentuated in the Afrotropics by the rapid agricultural expansion and intensification for the production of cash crops and by a comparative lack of research. In this study, we assessed how farming practices influence avian phylogenetic and functional diversity. We conducted point‐count surveys to assess avian diversity in monocultures of tea and mixed crop farming systems surrounding the Nyungwe rainforest in south‐west Rwanda, allowing us to investigate the drivers of avian diversity at farm level. Species composition was found to be moderately different between farm types, with mixed crop farms supporting higher phylogenetic diversity than tea plantations. There were no significant seasonal differences in species composition, functional or phylogenetic diversity. Overall, functional diversity did not differ between farm types, but the dispersion of trophic‐related traits was significantly higher in mixed crop farms. Both functional and phylogenetic diversity were influenced by floristic diversity, vegetation height, tree number, and elevation to varying degrees. Our results also (i) highlight the role of farmland heterogeneity (e.g., crop species composition, height, and tree cover extent) in encouraging avian functional and phylogenetic diversity in the Afrotropics and (ii) indicate that the generally negative biodiversity impacts of monoculture agriculture can be partially alleviated by extensive agroforestry with an emphasis on indigenous tree species.     

Deposition of condensed phosphate as an effect of varying sulfur deficiency in the cyanobacterium Synechococcus sp. (Anacystis nidulans)

Uptake of orthophosphate and deposition of condensed phosphate were investigated in cells of Synechococcus sp. (Anacystis nidulans) deficient in phosphorus or sulfur. When phosphorus was restored to phosphorus-starved cells, uptake was rapid and immediate, with the greatest accumulation occurring within the first hour. Uptake was optimum in the pH 7.5–8.5 range. Long-term (6-day) studies of uptake and deposition with cells exposed to a wide range of sulfur deficiency showed that both processes were greatest when the level of exogenous sulfur was reduced to zero. The increase in cellular phosphorus as determined chemically was in agreement with the increased number and size of polyphosphate bodies at the ultrastructural level. Possible mechanisms for the control of phosphorus uptake and condensed phosphate formation by exogenous sulfur are discussed.     

Anti-oxidation activity of ethanol extracts from natural thalli of lichens

Screening test on anti-oxidation activity using 1,1-diphenyl-2-picrylhydrazyl(DPPH) was performed for 99 ethanol extracts of 85 species of natural thalli of lichens in order to find novel anti-oxidation compounds.The 17 extracts of natural thalli showed high anti-oxidation activity.Among them,the activities of extracts from Hypogymnia vittata,Peltigera aphthosa,Nephromopsis ornata,Pseudevernia furfuracea,Cladonia vulcani and Peltigera elizabethae were higher.Extracts of Peltigera spp.showed higher activity than those of other genera.The ethanol extract of P.aphthosa had been separated into ethyl acetate-soluble and water-soluble fractions.Two anti-oxidative spots were found only in the water-soluble fractions by thin-layer chromatography.The compound in the lower spot had the same Rf value,UV spectrum,and color as authentic solorinine that was previously found as a unique quaternary ammonium compound from Peltigera spp.We now report that the hydrophilic lichen substance,solorinine showed a nearly same anti-oxidation activity(EC50=120?mol/Lol/L) as standard antioxidant Trolox(EC50=150?mol/L).     

A new isolate of the rhodospirillum fulvum group and its photosynthetic pigments

Summary The present paper reports the isolation of an obligate phototrophic bacterium which belongs to the Rhodospirillum fulvum-group on the basis of its colour, morphology, nutritional requirements and strictly anaerobic nature. p-Aminobenzoic acid was shown to be the only growth factor required. Rhsp. fulvum synthesizes bacteriochlorophyll a as its only chlorophyllous pigments. The carotenoid composition comprises lycopene (I) and rhodopin (II) as the major components; traces of 1,2,1,2-tetrahydro-1,1-dihydroxy-lycopene (III) were also present.

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Zusammenfassung Es wird die Isolierung eines obligat phototrophen Bakteriums beschrieben, welches auf Grund seiner Farbe, Morphologie, Nährstoff-Bedürfnisse und streng anaeroben Lebensweise in die Rhodospirillum fulvum-Gruppe eingeordnet wird. Als einzigen Wachstumsfaktor benötigt der Stamm p-Aminobenzoesäure. Rhsp. fulvum bildet Bacteriochlorophyll a als einzigen chlorophyllartigen Farbstoff. Die Hauptmenge der Carotinoide besteht aus Lycopin (I) und Rhodopin (II); es sind außerdem Spuren von 1,2,12-Tetrahydro-1,1-dihydroxy-Lycopin (III) nachgewiesen.

     

X-Ray Crystal Structure of a Highly Functionalized Thiophene as a New Backbone Amide Linker for Solid-phase Peptide Synthesis. Relationship between Crystal Structure and Reactivity

The development of new linkers (handles) for solid-phase synthesis provides new chemical opportunities for peptide synthesis. To understand the chemical properties of a recently developed backbone amide linker from a structural perspective, the crystal structure of S-((5-formyl-3,4-ethylenedioxy)thiophene-2-yl)-3-thiopropionic acid (T-BAL2) was studied. Specifically, we wished to address whether this highly substituted thiophene retained planarity in the aromatic ring as well as between the aromatic ring and the aldehyde carbonyl. Furthermore, we sought an explanation for the relatively low reactivity in reductive aminations of the thienylaldehyde with amines in solution and on solid phase. Based on the crystal structure of T-BAL2, the thienyl-C (aldehyde) and C–O (aldehyde) bond lengths were applied as measures for the electron-deficiency (electrophilicity) of the aldehyde and compared to similar bond lengths found in previously reported formylated homo- and hetero-aromatic systems, which show significantly higher reactivity towards imine formation. The bond lengths found in the present structure are in accordance with normal C–C single bond and C–O double bond lengths. The high similarity in aldehyde bond lengths in the present system and in the reported systems indicates similar electron distribution in these systems. The lower reactivity of the present system may therefore not be attributed to electronic factors.