Microhabitat partitioning in seagrass mesograzers is driven by consistent species choices across multiple predator and competitor contexts

Explanations for the coexistence of multiple species from the same functional group or taxonomic clade frequently include fine‐scale resource partitioning. However, despite the hypothesized importance of niche partitioning, we know relatively little about the underlying mechanisms. For example, differences in resource use may be fixed consequences of organism traits, or they may be achieved via context‐dependent behaviors. In this study we investigated mechanisms of microhabitat partitioning using eight species of marine mesograzers inhabiting seagrass and algae habitats, using laboratory trials to measure microhabitat use in the presence and absence of both predators and competitors. We found clear evidence for microhabitat partitioning between the species, which account for over 60% of the mesograzers commonly found in this system and vary in both body size and the ability to build tubes on habitat substrates. Species‐specific microhabitat use was poorly predicted by these two traits, but remained remarkably consistent across contexts. Habitat use was not affected by the presence of fish predators common in this system, even though predation pressure is thought to place strong constraints on microhabitat in communities of plant‐associated arthropods. The presence of competing species also did not affect the relative separation of microhabitat use. Behavioral responses to potential competitors did cause significant changes in microhabitat use in all of the smallest species, but these changes did not depend on competitor identity and were relatively small compared to among‐species patterns of microhabitat partitioning. The consistency of species‐specific microhabitat use, regardless of the presence of predators or competitors, should make coexistence most likely among species that differ in these choices. For these species, it appears that the benefits accrued from their selected microhabitats are not affected by species interactions, or that any benefits of alternative microhabitat use are outweighed by risks associated with movement.     

The effect of seasonality upon the development of lotic biofilms and microbial biostabilisation

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Pore formation by GSDMD is the effector mechanism of pyroptosis

Pyroptosis is a unique, pro‐inflammatory form of lytic cell death that is initiated by the activation of inflammatory caspases. The caspase substrate gasdermin D (GSDMD) plays a critical function in pyroptosis, yet the precise mode of action of this molecule in cell death execution remained unclear. Several recent reports, including a The EMBO Journal article, show that the caspase‐matured N‐terminal fragment of GSDMD is recruited to lipid membranes to form pore‐like structures, which constitutes the key effector mechanism of pyroptotic cell death.     

Introducing an algal carbon‐concentrating mechanism into higher plants: location and incorporation of key components

Many eukaryotic green algae possess biophysical carbon‐concentrating mechanisms (CCMs) that enhance photosynthetic efficiency and thus permit high growth rates at low CO₂ concentrations. They are thus an attractive option for improving productivity in higher plants. In this study, the intracellular locations of ten CCM components in the unicellular green alga Chlamydomonas reinhardtii were confirmed. When expressed in tobacco, all of these components except chloroplastic carbonic anhydrases CAH3 and CAH6 had the same intracellular locations as in Chlamydomonas. CAH6 could be directed to the chloroplast by fusion to an Arabidopsis chloroplast transit peptide. Similarly, the putative inorganic carbon (Ci) transporter LCI1 was directed to the chloroplast from its native location on the plasma membrane. CCP1 and CCP2 proteins, putative Ci transporters previously reported to be in the chloroplast envelope, localized to mitochondria in both Chlamydomonas and tobacco, suggesting that the algal CCM model requires expansion to include a role for mitochondria. For the Ci transporters LCIA and HLA3, membrane location and Ci transport capacity were confirmed by heterologous expression and H¹⁴CO₃^‐ uptake assays in Xenopus oocytes. Both were expressed in Arabidopsis resulting in growth comparable with that of wild‐type plants. We conclude that CCM components from Chlamydomonas can be expressed both transiently (in tobacco) and stably (in Arabidopsis) and retargeted to appropriate locations in higher plant cells. As expression of individual Ci transporters did not enhance Arabidopsis growth, stacking of further CCM components will probably be required to achieve a significant increase in photosynthetic efficiency in this species.     

Inducible gene modification in the gastric epithelium of Tff1‐CreERT2, Tff2‐rtTA,Tff3‐luc mice

Temporal and spatial regulation of genes mediated by tissue‐specific promoters and conditional gene expression systems provide a powerful tool to study gene function in health, disease, and during development. Although transgenic mice expressing the Cre recombinase in the gastric epithelium have been reported, there is a lack of models that allow inducible and reversible gene modification in the stomach. Here, we exploited the gastrointestinal epithelium‐specific expression pattern of the three trefoil factor (Tff) genes and bacterial artificial chromosome transgenesis to generate a novel mouse strain that expresses the CreERT2 recombinase and the reverse tetracycline transactivator (rtTA). The Tg(Tff1‐CreERT2;Tff2‐rtTA;Tff3‐Luc) strain confers tamoxifen‐inducible irreversible somatic recombination and allows simultaneous doxycycline‐dependent reversible gene activation in the gastric epithelium of developing and adult mice. This strain also confers luciferase activity to the intestinal epithelium to enable in vivo bioluminescence imaging. Using fluorescent reporters as conditional alleles, we show Tff1‐CreERT2 and Tff2‐rtTA transgene activity in a partially overlapping subset of long‐term regenerating gastric stem/progenitor cells. Therefore, the Tg(Tff1‐CreERT2;Tff2‐rtTA;Tff3‐Luc) strain can confer intermittent transgene expression to gastric epithelial cells that have undergone previous gene modification, and may be suitable to genetically model therapeutic intervention during development, tumorigenesis, and other genetically tractable diseases. Birth Defects Research (Part A) 106:626–635, 2016. © 2016 Wiley Periodicals, Inc.     

A bootstrap-aggregated hybrid semi-parametric modeling framework for bioprocess development

Bioprocess and Biosystems Engineering - Hybrid semi-parametric modeling, combining mechanistic and machine-learning methods, has proven to be a powerful method for process development. This paper...     

Sequentially Deposited versus Conventional Nonfullerene Organic Solar Cells: Interfacial Trap States,Vertical Stratification,and Exciton Dissociation

Bulk heterojunction (BHJ) nonfullerene organic solar cells prepared from sequentially deposited donor and acceptor layers (sq‐BHJ) have recently been shown to be highly efficient, environmentally friendly, and compatible with large area and roll‐to‐roll fabrication. However, the related photophysics at donor‐acceptor interface and the vertical heterogeneity of donor‐acceptor distribution, critical for exciton dissociation and device performance, have been largely unexplored. Herein, steady‐state and time‐resolved optical and electrical techniques are employed to characterize the interfacial trap states. Correlating with the luminescent efficiency of interfacial states and its nonradiative recombination, interfacial trap states are characterized to be about 40% more populated in the sq‐BHJ devices than the as‐cast BHJ (c‐BHJ), which probably limits the device voltage output. Cross‐sectional energy‐dispersive X‐ray spectroscopy and ultraviolet photoemission spectroscopy depth profiling directly visualize the donor–acceptor vertical stratification with a precision of 1–2 nm. From the proposed “needle” model, the high exciton dissociation efficiency is rationalized. This study highlights the promise of sequential deposition to fabricate efficient solar cells, and points toward improving the voltage output and overall device performance via eliminating interfacial trap states.     

Methane yield and species diversity dynamics of perennial wild plant mixtures established alone,under cover crop maize (Zea mays L.), and after spring barley (Hordeum vulgare L.)

The cultivation of perennial wild plant mixtures (WPMs) in biogas cropping systems dominated by maize (Zea mays L.) restores numerous ecosystem functions and improves both spatial and temporal agrobiodiversity. In addition, the colorful appearance of WPM can help enhance landscape beauty. However, their methane yield per hectare (MYH) varies greatly and amounts to only about 50% that of maize. This study aimed at decreasing MYH variability and increasing accumulated MYH of WPM by optimizing the establishment method. A field trial was established in southwest Germany in 2014, and is still running. It tested the effects of three WPM establishment procedures (E1: alone [without maize, in May], E2: undersown in cover crop maize [in May], E3: WPM sown after whole‐crop harvest of spring barley [Hordeum vulgare L.] in June) on both MYH and species diversity of two WPMs [S1, S2]). Mono‐cropped maize and cup plant (Silphium perfoliatum L.) were used as reference crops. Of the WPM treatments tested, S2E2 achieved the highest (19,296 , 60.5% of maize) and S1E1 the lowest accumulated MYH (8,156 , 25.6% of maize) in the years 2014–2018. Cup plant yielded slightly higher than S2E2 (19,968 , 62.6% of maize). In 2014, the WPM sown under maize did not significantly affect the cover crop performance. From 2015 onward, E1 and E2 had comparable average annual MYH and average annual number of WPM species. With a similar accumulated MYH but significantly higher number of species (3.5–10.2), WPM S2E2 outperformed cup plant. Overall, the long‐term MYH performance of WPM cultivation for biogas production can be significantly improved by undersowing with maize as cover crop. This improved establishment method could help facilitate the implementation of WPM cultivation for biogas production and thus reduce the trade‐off between bioenergy and biodiversity.