Regulation of phenylpropanoid metabolism by exogenous precursors in axenic cultures of Sphagnum fallax

Sphagnum plantlets, cultivated in continuous-feed bioreactors, are characterised by high levels of free endogenous phenolics and a pronounced excretion of some phenolics into the effluent culture medium. The transfer of Sphagnum fallax, precultivated in continuous-feed bioreactors, to batch cultures resulted in an increased flux through phenylpropanoid metabolism and an accumulation of p-coumaric acid to 0.1 μM and of trans-sphagnum acid up to 0.5 μM in the external medium [³H]-labelled L-phenylalanine (7.7 GBq mol^?1) was rapidly taken up, resulting in an enhanced synthesis and excretion of p-coumaric and trans-sphagnum acid. Specific activities were 6.9 and 5.4 GBq mol^?1, respectively, for these cinnamic acids excreted into the external medium. Endogenous pools of trans-cinnamic and p-coumaric acid did not increase and no labelling could be detected in these compounds. Cell wall-bound activity amounted to ca 14% of the applied activity after 48 h of incubation, 59% of which was recovered in dioxane/2 M HCl extracts of the cell wall. Exogenously applied trans-cinnamic acid (0.1 mM) was taken up to 46% and resulted in a transient endogenous accumulation of trans-cinnamic acid, the level of free endogenous p-coumaric and trans-sphagnum acid was found to have decreased. The concentrations of p-coumaric and trans-sphagnum acid in the culture medium rose to 17 and 2.4 μM, respectively, after 48 h of incubation in 0.1 mMtrans-cinnamic acid. Exogenously applied p-coumaric acid (0.1 mM) was taken up to 79% from the incubation solution but not stored endogenously, as metabolic products trans-sphagnum acid and an unknown p-coumaric acid-conjugate accumulated in the external medium and endogenously. These results give evidence for the biosynthetical route from phenylalanine to sphagnum acid and a channelling of pathway intermediates by the enzymes L-phenylalanine ammonia-lyase (EC 4.3.1.5) and cinnamic acid 4-hydroxylase (EC 1.14.13.11).     

Macroecology in the age of Big Data – Where to go from here?

Recent years have seen an exponential increase in the amount of data available in all sciences and application domains. Macroecology is part of this “Big Data” trend, with a strong rise in the volume of data that we are using for our research. Here, we summarize the most recent developments in macroecology in the age of Big Data that were presented at the 2018 annual meeting of the Specialist Group Macroecology of the Ecological Society of Germany, Austria and Switzerland (GfÖ). Supported by computational advances, macroecology has been a rapidly developing field over recent years. Our meeting highlighted important avenues for further progress in terms of standardized data collection, data integration, method development and process integration. In particular, we focus on (a) important data gaps and new initiatives to close them, for example through space- and airborne sensors, (b) how various data sources and types can be integrated, (c) how uncertainty can be assessed in data-driven analyses and (d) how Big Data and machine learning approaches have opened new ways of investigating processes rather than simply describing patterns. We discuss how Big Data opens up new opportunities, but also poses new challenges to macroecological research. In the future, it will be essential to carefully assess data quality, the reproducibility of data compilation and analytical methods, and the communication of uncertainties. Major progress in the field will depend on the definition of data standards and workflows for macroecology, such that scientific quality and integrity are guaranteed, and collaboration in research projects is made easier.     

Core Hunter: an algorithm for sampling genetic resources based on multiple genetic measures

Background  

Existing algorithms and methods for forming diverse core subsets currently address either allele representativeness (breeder's preference) or allele richness (taxonomist's preference). The main objective of this paper is to propose a powerful yet flexible algorithm capable of selecting core subsets that have high average genetic distance between accessions, or rich genetic diversity overall, or a combination of both.     

<Superscript>15</Superscript>N natural abundance of fossil peat reflects the influence of animal-derived nitrogen on vegetation

'¹⁵N signatures of fossil peat were used to interpret past ecosystem processes on tectonically active subantarctic Macquarie Island. By comparing past vegetation reconstructed from the fossil record with present-day vegetation analogues, our evidence strongly suggests that changes in the '¹⁵N signatures of fossil peat at this location reflect mainly past changes in the proportion of plant nitrogen derived from animal sources. Associated with uplift above sea level over the past 8,500 years, fossil records in two peat deposits on the island chronicle a change from coastal vegetation with fur and elephant seal disturbance to the existing inland herbfield. Coupled with this change are synchronous changes in the '¹⁵N signatures of peat layers. At two sites ¹⁵N-enriched peat '¹⁵N signatures of up to +17‰ were associated with a high abundance of pollen of the nitrophile Callitriche antarctica (Callitrichaceae). At one site fossil seal hair was also associated with enriched peat '¹⁵N. Less ¹⁵N enriched '¹⁵N signatures (e.g. -1.9‰ to +3.9‰) were measured in peat layers which lacked animal associated C. antarctica and Acaena spp. Interpretation of a third peat profile indicates continual occupation of a ridge site by burrowing petrels for most of the Holocene. We suggest that ¹⁵N signatures of fossil peat remained relatively stable with time once deposited, providing a significant new tool for interpreting the palaeoecology.     

Drosophila ATP6AP2/VhaPRR functions both as a novel planar cell polarity core protein and a regulator of endosomal trafficking

Planar cell polarity (PCP) controls the orientation of cells within tissues and the polarized outgrowth of cellular appendages. So far, six PCP core proteins including the transmembrane proteins Frizzled (Fz), Strabismus (Stbm) and Flamingo (Fmi) have been identified. These proteins form asymmetric PCP domains at apical junctions of epithelial cells. Here, we demonstrate that VhaPRR, an accessory subunit of the proton pump V‐ATPase, directly interacts with the protocadherin Fmi through its extracellular domain. It also shows a striking co‐localization with PCP proteins during all pupal wing stages in Drosophila. This localization depends on intact PCP domains. Reversely, VhaPRR is required for stable PCP domains, identifying it as a novel PCP core protein. VhaPRR performs an additional role in vesicular acidification as well as endolysosomal sorting and degradation. Membrane proteins, such as E‐Cadherin and the Notch receptor, accumulate at the surface and in intracellular vesicles of cells mutant for VhaPRR. This trafficking defect is shared by other V‐ATPase subunits. By contrast, the V‐ATPase does not seem to have a direct role in PCP regulation. Together, our results suggest two roles for VhaPRR, one for PCP and another in endosomal trafficking. This dual function establishes VhaPRR as a key factor in epithelial morphogenesis.     

Low rates of iridoid glycoside hydrolysis in two Longitarsus leaf beetles with different feeding specialization confer tolerance to iridoid glycoside containing host plants

Iridoid glycosides are plant defence compounds that are deterrent and/or toxic for unadapted herbivores but are readily sequestered by dietary specialists of different insect orders. Hydrolysis of iridoid glycosides by β‐glucosidase leads to protein denaturation. Insect digestive β‐glucosidases thus have the potential to mediate plant–insect interactions. In the present study, mechanisms associated with iridoid glycoside tolerance are investigated in two closely‐related leaf beetle species (Coleoptera: Chrysomelidae) that feed on iridoid glycoside containing host plants. The polyphagous Longitarsus luridus Scopoli does not sequester iridoid glycosides, whereas the specialist Longitarsus tabidus Fabricius sequesters these compounds from its host plants. To study whether the biochemical properties of their β‐glucosidases correspond to the differences in feeding specialization, the number of β‐glucosidase isoforms and their kinetic properties are compared between the two beetle species. To examine the impact of iridoid glycosides on the β‐glucosidase activity of the generalist, L. luridus beetles are kept on host plants with or without iridoid glycosides. Furthermore, β‐glucosidase activities of both species are examined using an artificial β‐glucosidase substrate and the iridoid glycoside aucubin present in their host plants. Both species have one or two β‐glucosidases with different substrate affinities. Interestingly, host plant use does not influence the specific β‐glucosidase activities of the generalist. Both species hydrolyse aucubin with a much lower affinity than the standard substrate. The neutral pH reduces the β‐glucosidase activity of the specialist beetles by approximately 60% relative to its pH optimum. These low rates of aucubin hydrolysis suggest that the ability to sequester iridoid glycosides has evolved as a key to potentially preventing iridoid glycoside hydrolysis by plant‐derived β‐glucosidases.     

The Focal Adhesion: A Regulated Component of Aortic Stiffness

Increased aortic stiffness is an acknowledged predictor and cause of cardiovascular disease. The sources and mechanisms of vascular stiffness are not well understood, although the extracellular matrix (ECM) has been assumed to be a major component. We tested here the hypothesis that the focal adhesions (FAs) connecting the cortical cytoskeleton of vascular smooth muscle cells (VSMCs) to the matrix in the aortic wall are a component of aortic stiffness and that this component is dynamically regulated. First, we examined a model system in which magnetic tweezers could be used to monitor cellular cortical stiffness, serum-starved A7r5 aortic smooth muscle cells. Lysophosphatidic acid (LPA), an activator of myosin that increases cell contractility, increased cortical stiffness. A small molecule inhibitor of Src-dependent FA recycling, PP2, was found to significantly inhibit LPA-induced increases in cortical stiffness, as well as tension-induced increases in FA size. To directly test the applicability of these results to force and stiffness development at the level of vascular tissue, we monitored mouse aorta ring stiffness with small sinusoidal length oscillations during agonist-induced contraction. The alpha-agonist phenylephrine, which also increases myosin activation and contractility, increased tissue stress and stiffness in a PP2- and FAK inhibitor 14-attenuated manner. Subsequent phosphotyrosine screening and follow-up with phosphosite-specific antibodies confirmed that the effects of PP2 and FAK inhibitor 14 in vascular tissue involve FA proteins, including FAK, CAS, and paxillin. Thus, in the present study we identify, for the first time, the FA of the VSMC, in particular the FAK-Src signaling complex, as a significant subcellular regulator of aortic stiffness and stress.