Down-Regulation of ZmEXPB6 (Zea mays β-Expansin 6) Protein Is Correlated with Salt-mediated Growth Reduction in the Leaves of Z. mays L.

The salt-sensitive crop Zea mays L. shows a rapid leaf growth reduction upon NaCl stress. There is increasing evidence that salinity impairs the ability of the cell walls to expand, ultimately inhibiting growth. Wall-loosening is a prerequisite for cell wall expansion, a process that is under the control of cell wall-located expansin proteins. In this study the abundance of those proteins was analyzed against salt stress using gel-based two-dimensional proteomics and two-dimensional Western blotting. Results show that ZmEXPB6 (Z. mays β-expansin 6) protein is lacking in growth-inhibited leaves of salt-stressed maize. Of note, the exogenous application of heterologously expressed and metal-chelate-affinity chromatography-purified ZmEXPB6 on growth-reduced leaves that lack native ZmEXPB6 under NaCl stress partially restored leaf growth. In vitro assays on frozen-thawed leaf sections revealed that recombinant ZmEXPB6 acts on the capacity of the walls to extend. Our results identify expansins as a factor that partially restores leaf growth of maize in saline environments.     

Late Quaternary paleoenvironmental records from the western Lena Delta,Arctic Siberia

The three main Lena Delta terraces were formed during different stages of the late Quaternary. While only the first floodplain terrace is connected with active deltaic processes, the second and third terraces, which dominate the western part of the delta, are erosional remnants of arctic paleolandscapes affected by periglacial processes. The landscape dynamics of the second and the third terraces, and their relationship to each other, are of particular importance in any effort to elucidate the late Quaternary paleoenvironment of western Beringia.Multidisciplinary studies of permafrost deposits on the second terrace were carried out at several sites of the Arga Complex, named after the largest delta island, Arga–Muora–Sise. The frozen sediments predominantly consist of fluvial sands several tens of meters thick, radiocarbon-dated from > 52 to 16 kyr BP. These sands were deposited under changing fluvial conditions in a dynamic system of shifting river channels, and have been additionally modified by synsedimentary and postsedimentary cryogenesis. Later thermokarst processes affected this late Pleistocene fluvial landscape during the Lateglacial and the Holocene. In addition, eolian activity reworked the fluvial sands on exposed surfaces at least since the Lateglacial, resulting in dune formation in some areas. Contrary to the Arga Complex, the third terrace is mainly composed of polygenetic alluvial and proluvial ice-rich permafrost sequences (Ice Complex deposits) radiocarbon-dated from 50 to 17 kyr BP which cover older fluvial sand units luminescence-dated to about 100–50 kyr BP. Paleoecological records reflect tundra-steppe conditions that varied locally, depending on landscape dynamics, during the Marine Isotope Stage (MIS) 4 and 3 periods, and a persistent change to shrub and arctic tundra during Lateglacial and Holocene periods.The study results indicate a continuous fluvial sedimentation environment for the Laptev Sea shelf in the region of the second Lena Delta terrace during the late Pleistocene, and confirm the presence of a dynamic channel system of the paleo-Lena River that flowed at the same time as the nearby subaerial Ice Complex deposits were being formed.     

Identification and reciprocal introgression of a QTL affecting body mass in mice

The aim of this study was to examine the effects of a QTL in different genetic backgrounds. A QTL affecting body mass on chromosome 6 was identified in an F₂ cross between two lines of mice that have been divergently selected for this trait. The effect of the QTL on mass increased between 6 and 10 weeks of age and was not sex-specific. Body composition analysis showed effects on fat-free dry body mass and fat mass. To examine the effect of this QTL in different genetic backgrounds, the high body mass sixth chromosome was introgressed into the low body mass genetic background and vice versa by repeated marker-assisted backcrossing. After three generations of backcrossing, new F₂ populations were established within each of the introgression lines by crossing individuals that were heterozygous across the sixth chromosome. The estimated additive effect of the QTL on 10-week body mass was similar in both genetic backgrounds and in the original F₂ population (i.e., ~0.4 phenotypic standard deviations); no evidence of epistatic interaction with the genetic background was found. The 95% confidence interval for the location of the QTL was refined to a region of approximately 7 cM between D6Mit268 and D6Mit123.     

Experimental ecology at deep-sea hydrothermal vents: a perspective

In situ and laboratory experiments conducted over the past quarter of a century have greatly increased our understanding of the ecology of deep-sea hydrothermal systems. Early experiments suggested that chemosynthetic primary production constituted the principal source of organic matter for biological communities associated with vents, although subsequent studies have revealed many complexities associated with interactions between microbes and higher organisms inhabiting these ecosystems. A diversity of host-microbial symbiont relationships has been identified and experimental studies have revealed the exquisite physiological adaptations within the giant tubeworm, Riftia pachyptila, for the uptake, fixation, and assimilation of carbon. In vitro experiments demonstrated the unusual sulfide binding properties of tubeworm hemoglobin that prevent inhibition of the cytochrome-c oxidase enzyme system during transport of sulfide to symbiont-bearing tissues. Studies of respiration and growth of several species of vent organisms conducted over the past two decades transformed earlier views that low metabolism and slow growth are characteristics of all organisms inhabiting all deep-sea environments. Results of recent experiments suggest that metabolic rates correlate with the degree of mobility of the organisms rather than with any specific attribute of the deep-sea environment itself, and growth rates of certain vent organisms (e.g., R. pachyptila) were found to be among the highest in any marine environments. While extreme thermal tolerance has been suggested as characteristic of certain vent fauna (e.g., alvinellid polychaetes and alvinocarid shrimp), the majority of vent metazoans live at temperatures below 20 °C and additional experiments are necessary to reconcile field experiments documenting thermal tolerance in situ, thermal tolerance in vivo, and thermal sensitivity of biochemical constituents of vent organisms. Transplantation and clearance experiments, as well as in situ characterization of vent fluid chemistry, have greatly increased our understanding of organism–environment interactions. Early analyses of metazoan egg size and larval morphology, coupled with in vivo larval culture experiments, available physical oceanographic data, and genetic studies of gene flow, have contributed greatly to our understanding of mechanisms of dispersal between widely separated vent sites. The documentation of invertebrate colonization and succession of new vents following a volcanic eruption, and a series of manipulative field experiments, provide considerable insights into the relative roles of abiotic conditions and biotic interactions in structuring vent communities. Recent and emerging technological developments, such as in situ chemical analyzers, observatory approaches, and laboratory-based pressure culture systems, should provide invaluable new experimental tools for tackling many remaining questions concerning the ecology of deep-sea hydrothermal systems.     

CyDisCo production of functional recombinant SARS‐CoV‐2 spike receptor binding domain

The COVID‐19 pandemic caused by SARS‐CoV‐2 has applied significant pressure on overtaxed healthcare around the world, underscoring the urgent need for rapid diagnosis and treatment. We have developed a bacterial strategy for the expression and purification of a SARS‐CoV‐2 spike protein receptor binding domain (RBD) that includes the SD1 domain. Bacterial cytoplasm is a reductive environment, which is problematic when the recombinant protein of interest requires complicated folding and/or processing. The use of the CyDisCo system (cytoplasmic disulfide bond formation in E. coli) bypasses this issue by pre‐expressing a sulfhydryl oxidase and a disulfide isomerase, allowing the recombinant protein to be correctly folded with disulfide bonds for protein integrity and functionality. We show that it is possible to quickly and inexpensively produce an active RBD in bacteria that is capable of recognizing and binding to the ACE2 (angiotensin‐converting enzyme) receptor as well as antibodies in COVID‐19 patient sera.     

Experimental and computational studies of two new mono- and dinuclear iridium complexes containing a Buchwald biphenyl phosphine ligand

The reaction of [(η⁴-1,5-C₈H₁₂)₂Ir₂(μ-Cl)₂] with 2-di-t-butylphosphino-2′-methylbiphenyl (t-Bu₂Pbiph^Me) in the presence of AgBF₄ afforded the dichlorido-bridged Ir–Ag complex [(η⁴-1,5-C₈H₁₂)Ir(μ-Cl)₂Ag(t-Bu₂Pbiph^Me)] (1) which was fully characterized by a single crystal X-ray diffraction study. Sequential treatment of the diiridium precursor first with the silver salt and then with the phosphine yielded cyclometalated [(η⁴-1,5-C₈H₁₂)Ir(t-Bu₂Pbiph^Me–H⁺)] (2). Detailed DFT calculations gave evidence that the phosphine ligand of 2 forms a strained four-membered iridaheterocycle through orthometalation rather than a sterically congested six-membered chelate structure through C–H activation on the remote phenyl ring. The phosphonium salt [t-Bu₂P(H)biph^Me]BF₄ was isolated as a by-product of the preparations of 1 and 2; its crystal structure was determined.     

Homogeneous CO hydrogenation and transfer hydrogenation catalyzed by ruthenium(II) complexes containing optically active Ph2PCH(Ph)CH(Me)NH2 and 1,2-C5H8(PPh2)2 ligands

Combination of (1S,2S)-cyclopentanediylbis(diphenylphosphine) with [Ru(η⁴-C₈H₁₂){η³-(CH₂)₂CMe}₂] afforded the chelate complex [Ru{η³-(CH₂)₂CMe}₂{(1S,2S)-C₅H₈(PPh₂)₂}] (1), which gave (OC-6-13)-[RuCl₂{(1S,2S)-C₅H₈(PPh₂)₂}{(1S,2S)-Ph₂PCH(Ph)CH(Me)NH₂}] (2) upon reaction with methanolic HCl in acetone, followed by the addition of the β-aminophosphine in DMF. The (P ∩ N)₂-chelated complexes (OC-6-13)-[RuCl₂{(1S,2S)-Ph₂PCH(Ph)CH(Me)NH₂}₂] (3) and (OC-6-13)-[RuCl₂{(1R,2S)-Ph₂PCH(Ph)CH(Me)NH₂}₂] (4) resulted from RuCl₃ · 3H₂O and the P,N ligands under reducing conditions. The crystal structures of 3 and 4 were determined by single-crystal X-ray diffraction. Following activation by KOBu-t in isopropanol, compounds 2–4 catalyzed the enantioselective transfer hydrogenation of acetophenone with i-PrOH as the hydrogen source as well as the direct hydrogenation of the ketone by H₂ in low to moderate e.e. (up to 67%).     

Plants,microorganisms, and soil temperatures contribute to a decrease in methane fluxes on a drained Arctic floodplain

As surface temperatures are expected to rise in the future, ice‐rich permafrost may thaw, altering soil topography and hydrology and creating a mosaic of wet and dry soil surfaces in the Arctic. Arctic wetlands are large sources of CH₄, and investigating effects of soil hydrology on CH₄ fluxes is of great importance for predicting ecosystem feedback in response to climate change. In this study, we investigate how a decade‐long drying manipulation on an Arctic floodplain influences CH₄‐associated microorganisms, soil thermal regimes, and plant communities. Moreover, we examine how these drainage‐induced changes may then modify CH₄ fluxes in the growing and nongrowing seasons. This study shows that drainage substantially lowered the abundance of methanogens along with methanotrophic bacteria, which may have reduced CH₄ cycling. Soil temperatures of the drained areas were lower in deep, anoxic soil layers (below 30 cm), but higher in oxic topsoil layers (0–15 cm) compared to the control wet areas. This pattern of soil temperatures may have reduced the rates of methanogenesis while elevating those of CH₄ oxidation, thereby decreasing net CH₄ fluxes. The abundance of Eriophorum angustifolium, an aerenchymatous plant species, diminished significantly in the drained areas. Due to this decrease, a higher fraction of CH₄ was alternatively emitted to the atmosphere by diffusion, possibly increasing the potential for CH₄ oxidation and leading to a decrease in net CH₄ fluxes compared to a control site. Drainage lowered CH₄ fluxes by a factor of 20 during the growing season, with postdrainage changes in microbial communities, soil temperatures, and plant communities also contributing to this reduction. In contrast, we observed CH₄ emissions increased by 10% in the drained areas during the nongrowing season, although this difference was insignificant given the small magnitudes of fluxes. This study showed that long‐term drainage considerably reduced CH₄ fluxes through modified ecosystem properties.     

Linking microbial diversity and functionality of arctic glacial surface habitats

Distinct microbial habitats on glacial surfaces are dominated by snow and ice algae, which are the critical players and the dominant primary colonisers and net producers during the melt season. Here for the first time we have evaluated the role of these algae in association with the full microbial community composition (i.e., algae, bacteria, archaea) in distinct surface habitats and on 12 glaciers and permanent snow fields in Svalbard and Arctic Sweden. We cross‐correlated these data with the analyses of specific metabolites such as fatty acids and pigments, and a full suite of potential critical physico‐chemical parameters including major and minor nutrients, and trace metals. It has been shown that correlations between single algal species, metabolites, and specific geochemical parameters can be used to unravel mixed metabolic signals in complex communities, further assign them to single species and infer their functionality. The data also clearly show that the production of metabolites in snow and ice algae is driven mainly by nitrogen and less so by phosphorus limitation. This is especially important for the synthesis of secondary carotenoids, which cause a darkening of glacial surfaces leading to a decrease in surface albedo and eventually higher melting rates.