Induced gene expression in wheat seedlings treated with a crude extract of Agapanthus africanus L. prior to leaf rust infection

It was previously shown that a crude extract of Agapanthus africanus L. (Hoffman), applied as a foliar spray to wheat (Triticum aestivum L.) seedlings, significantly increased the in vitro activities of three pathogenesis related (PR) proteins (β-1,3-glucanase, chitinase and peroxidase). This was the case in both susceptible and resistant wheat lines whether the plants were uninfected or infected with leaf rust (Puccinia triticina). The aim of this study was to determine the influence of the A. africanus extract on both the intercellular PR-protein profile and PR gene expression in leaf rust infected wheat lines. Pretreatment of infected resistant and susceptible wheat with the extract led to increased β-1,3-glucanase levels that were higher as compared to the untreated controls. Similarly, treatment with the extract led to greater expression of both the PR3 and PR9 genes in infected resistant and susceptible seedlings as compared to the controls. This is also applied to a retrotransposon protein encoding gene whose expression was strongly induced following extract treatment. The induced expression of all these defence-related genes suggests that the crude A. africanus extract has the ability to prime the resistance response of wheat prior to leaf rust infection.Keywords: Wheat leaf rust, induced resistance, priming, gene expression, immunoblotting, crude Agapanthus africanus extractAfrican Journal of Biotechnology Vol. 12(20), pp. 2876-288

Visualizing and trapping transient oligomers in amyloid assembly pathways

Oligomers which form during amyloid fibril assembly are considered to be key contributors towards amyloid disease. However, understanding how such intermediates form, their structure, and mechanisms of toxicity presents significant challenges due to their transient and heterogeneous nature. Here, we discuss two different strategies for addressing these challenges: use of (1) methods capable of detecting lowly-populated species within complex mixtures, such as NMR, single particle methods (including fluorescence and force spectroscopy), and mass spectrometry; and (2) chemical and biological tools to bias the amyloid energy landscape towards specific oligomeric states. While the former methods are well suited to following the kinetics of amyloid assembly and obtaining low-resolution structural information, the latter are capable of producing oligomer samples for high-resolution structural studies and inferring structure-toxicity relationships. Together, these different approaches should enable a clearer picture to be gained of the nature and role of oligomeric intermediates in amyloid formation and disease

Modulation of Amyloidogenic Protein Self-Assembly Using Tethered Small Molecules

Protein–protein interactions (PPIs) are involved in many of life’s essential biological functions yet are also an underlying cause of several human diseases, including amyloidosis. The modulation of PPIs presents opportunities to gain mechanistic insights into amyloid assembly, particularly through the use of methods which can trap specific intermediates for detailed study. Such information can also provide a starting point for drug discovery. Here, we demonstrate that covalently tethered small molecule fragments can be used to stabilize specific oligomers during amyloid fibril formation, facilitating the structural characterization of these assembly intermediates. We exemplify the power of covalent tethering using the naturally occurring truncated variant (ΔN6) of the human protein β2-microglobulin (β2m), which assembles into amyloid fibrils associated with dialysis-related amyloidosis. Using this approach, we have trapped tetramers formed by ΔN6 under conditions which would normally lead to fibril formation and found that the degree of tetramer stabilization depends on the site of the covalent tether and the nature of the protein–fragment interaction. The covalent protein–ligand linkage enabled structural characterization of these trapped, off-pathway oligomers using X-ray crystallography and NMR, providing insight into why tetramer stabilization inhibits amyloid assembly. Our findings highlight the power of “post-translational chemical modification” as a tool to study biological molecular mechanisms

Dendritic cell-specific delivery of Flt3L by coronavirus vectors secures induction of therapeutic antitumor immunity

Efficacy of antitumor vaccination depends to a large extent on antigen targeting to dendritic cells (DCs). Here, we assessed antitumor immunity induced by attenuated coronavirus vectors which exclusively target DCs in vivo and express either lymphocyte- or DC-activating cytokines in combination with a GFP-tagged model antigen. Tracking of in vivo transduced DCs revealed that vectors encoding for Fms-like tyrosine kinase 3 ligand (Flt3L) exhibited a higher capacity to induce DC maturation compared to vectors delivering IL-2 or IL-15. Moreover, Flt3L vectors more efficiently induced tumor-specific CD8(+) T cells, expanded the epitope repertoire, and provided both prophylactic and therapeutic tumor immunity. In contrast, IL-2- or IL-15-encoding vectors showed a substantially lower efficacy in CD8(+) T cell priming and failed to protect the host once tumors had been established. Thus, specific in vivo targeting of DCs with coronavirus vectors in conjunction with appropriate conditioning of the microenvironment through Flt3L represents an efficient strategy for the generation of therapeutic antitumor immunity

Earth: Atmospheric Evolution of a Habitable Planet

Our present-day atmosphere is often used as an analog for potentially habitable exoplanets, but Earth's atmosphere has changed dramatically throughout its 4.5 billion year history. For example, molecular oxygen is abundant in the atmosphere today but was absent on the early Earth. Meanwhile, the physical and chemical evolution of Earth's atmosphere has also resulted in major swings in surface temperature, at times resulting in extreme glaciation or warm greenhouse climates. Despite this dynamic and occasionally dramatic history, the Earth has been persistently habitable--and, in fact, inhabited--for roughly 4 billion years. Understanding Earth's momentous changes and its enduring habitability is essential as a guide to the diversity of habitable planetary environments that may exist beyond our solar system and for ultimately recognizing spectroscopic fingerprints of life elsewhere in the Universe. Here, we review long-term trends in the composition of Earth's atmosphere as it relates to both planetary habitability and inhabitation. We focus on gases that may serve as habitability markers (CO2, N2) or biosignatures (CH4, O2), especially as related to the redox evolution of the atmosphere and the coupled evolution of Earth's climate system. We emphasize that in the search for Earth-like planets we must be mindful that the example provided by the modern atmosphere merely represents a single snapshot of Earth's long-term evolution. In exploring the many former states of our own planet, we emphasize Earth's atmospheric evolution during the Archean, Proterozoic, and Phanerozoic eons, but we conclude with a brief discussion of potential atmospheric trajectories into the distant future, many millions to billions of years from now. All of these 'Alternative Earth' scenarios provide insight to the potential diversity of Earth-like, habitable, and inhabited worlds.Comment: 34 pages, 4 figures, 4 tables. Review chapter to appear in Handbook of Exoplanet

O and H isotopic evidence for a mantle source of water in appinite magma: An example from the late Neoproterozoic Greendale Complex, Nova Scotia

Appinite suite rocks occur as small plutonic bodies, ranging from ultramafic to felsic in composition, that are characterized by abundant idiomorphic amphibole suggesting they are the products of water-rich mafic magmas. Appinites are also understood to record tectono-magmatic processes during the waning stages of subduction in convergent to collisional tectonic settings. Measuring D/H and&nbsp;18O/16O ratios of hornblende in appinitic rocks offers opportunities to constrain the sources of water (mantle, crustal, sea water and or meteoric) in the magma during its crystallization, and to shed light on the role of water as arc magmatism shuts down. The ca. 607&nbsp;Ma Greendale Complex in the Avalon terrane of Nova Scotia, Canada, is characterized by spectacular exposures of appinite suite rocks ranging from ultramafic to felsic in composition. Two populations of amphiboles are identified: one is characterized by &delta;18O values between 4.7 and 6.8&permil; and anomalously low &delta;D values (ca. &lt; &minus;90&permil;). These isotopic signatures are interpreted to represent incorporation of mantle-derived fluids into the crystal structure, possibly associated with mixing between a region of mantle upwelling and a subducting slab. This mixing process allows for hydration of the magma during its ascent into the overlying lithospheric mantle wedge. Some amphiboles retain mantle-like &delta;18O and &delta;D values, but others may have partially re-equilibrated during low T assimilation of supracrustal units (e.g. organic-rich sediments) and or fluids derived from such bodies. A second generation of hornblende yields &delta;18O varying from 0.9 to 4.6&permil; and &delta;D from ca. &minus;106 to &minus;64&permil;, which supports equilibration with fluids from crustal sources. Assimilation of volatiles sourced from previously hydrothermally altered intruded sheets and or country rock is interpreted to produce these second-generation isotopic signatures. Regional syntheses indicate that arc magmatism in the Avalon terrane ended with the generation of a transform system, implying the potential generation of a slab window behind that system. In that context, the Appinites in the Avalon terrane have previously been interpreted to have been emplaced after the cessation of subduction in a slab window or slab failure setting behind the transform system, in which asthenospheric upwelling generated juvenile magmas and/or facilitated melting of the overlying continental lithospheric mantle. Our &delta;D and &delta;18O data support this model and together with available Sm-Nd data, suggest asthenospheric upwelling triggered melting of the continental lithospheric mantle that was previously hydrated by subduction and this mantle-derived water contributed to the origin of appinites.</p

Towards Optimizing Peptide-Based Inhibitors of Protein-Protein Interactions: Predictive Saturation Variation Scanning (PreSaVS)

A simple-to-implement and experimentally validated computational workflow for sequence modification of peptide inhibitors of protein–protein interactions (PPIs) is described

In vivo characterization of the physicochemical properties of polymer-linked TLR agonists that enhance vaccine immunogenicity

The efficacy of vaccine adjuvants such as Toll-like receptor agonists (TLRa) can be improved through formulation and delivery approaches. Here, we attached small molecule TLR-7/8a to polymer scaffolds (polymer-TLR-7/8a) and evaluated how different physicochemical properties of the TLR-7/8a and polymer carrier influenced the location, magnitude and duration of innate immune activation in vivo. Particle formation by polymer-TLR-7/8a was the most important factor for restricting adjuvant distribution and prolonging activity in draining lymph nodes. The improved pharmacokinetic profile by particulate polymer-TLR-7/8a was also associated with reduced morbidity and enhanced vaccine immunogenicity for inducing antibodies and T cell immunity. We extended these findings to the development of a modular approach in which protein antigens are site-specifically linked to temperature-responsive polymer-TLR-7/8a adjuvants that self-assemble into immunogenic particles at physiologic temperatures in vivo. Our findings provide a chemical and structural basis for optimizing adjuvant design to elicit broad-based antibody and T cell responses with protein antigens