Changes in interactions between juniper and mistletoe mediated by shared avian frugivores: parasitism to potential mutualism

Although mistletoe is typically viewed as a parasite of juniper in a two-way interaction, its role may become neutral or even mutualistic when their common avian seed dispersing agents are considered as a three-way interaction. In the study area, wintering avian frugivores forage on both one-seed juniper (Juniperus monosperma) berries and on the fruit of its associated mistletoe (Phoradendron juniperinum). Three major findings emerged from our studies that support a three-way interaction and the hypothesis of conditional interactions. First, mistletoes provide a stable resource for shared avian seed dispersers; junipers do not. Whereas juniper berry production varied 10- to 15-fold over the 3 years of our study, mistletoe fruit abundance did not vary significantly. Second, the abundance of avian seed dispersal agents, such as Townsend's solitaires (Myadestes townsendi), is strongly tied to the abundance of juniper berries in mast years and mistletoe fruits in all years. In fact, the best overall predictor of their common avian seed dispersal agents was the abundance of mistletoe; stands with mistletoe attracted up to 3 times more avian frugivores than stands with little or no mistletoe. Thus, mistletoe berries can serve as the main attractor for birds that disperse juniper berries. Third, in agreement with the hypothesis that mistletoe can benefit junipers by attracting and supporting greater populations of avian seed dispersal agents, the number of juniper seedlings was more than 2-fold greater in stands with high mistletoe density compared with stands that had little or no mistletoe. Results suggest that the occurrence of a three-way interaction, in the presence of environmental variation (in this case, annual variation in juniper berry crops), may change the ecological roles of associated species. A conceptual model is presented to illustrate how the role of mistletoe may range from parasitic to mutualistic, while the role of avian seed dispersers may conversely range from mutualistic to parasitic, the latter by acting as vectors for the spread of mistletoe.     

Preface to Mechanisms of neuromuscular control. A Theme organized and edited by J. L. van Leeuwen

Preface to Mechanisms of neuromuscular control. A Theme organized and edited by J. L. van Leeuwen.     

Proteomic Profiling of the TRAF3 Interactome Network Reveals a New Role for the ER-to-Golgi Transport Compartments in Innate Immunity

Tumor Necrosis Factor receptor-associated factor-3 (TRAF3) is a central mediator important for inducing type I interferon (IFN) production in response to intracellular double-stranded RNA (dsRNA). Here, we report the identification of Sec16A and p115, two proteins of the ER-to-Golgi vesicular transport system, as novel components of the TRAF3 interactome network. Notably, in non-infected cells, TRAF3 was found associated with markers of the ER-Exit-Sites (ERES), ER-to-Golgi intermediate compartment (ERGIC) and the cis-Golgi apparatus. Upon dsRNA and dsDNA sensing however, the Golgi apparatus fragmented into cytoplasmic punctated structures containing TRAF3 allowing its colocalization and interaction with Mitochondrial AntiViral Signaling (MAVS), the essential mitochondria-bound RIG-I-like Helicase (RLH) adaptor. In contrast, retention of TRAF3 at the ER-to-Golgi vesicular transport system blunted the ability of TRAF3 to interact with MAVS upon viral infection and consequently decreased type I IFN response. Moreover, depletion of Sec16A and p115 led to a drastic disorganization of the Golgi paralleled by the relocalization of TRAF3, which under these conditions was unable to associate with MAVS. Consequently, upon dsRNA and dsDNA sensing, ablation of Sec16A and p115 was found to inhibit IRF3 activation and anti-viral gene expression. Reciprocally, mild overexpression of Sec16A or p115 in Hec1B cells increased the activation of IFNβ, ISG56 and NF-κB -dependent promoters following viral infection and ectopic expression of MAVS and Tank-binding kinase-1 (TBK1). In line with these results, TRAF3 was found enriched in immunocomplexes composed of p115, Sec16A and TBK1 upon infection. Hence, we propose a model where dsDNA and dsRNA sensing induces the formation of membrane-bound compartments originating from the Golgi, which mediate the dynamic association of TRAF3 with MAVS leading to an optimal induction of innate immune responses.     

Genome-wide methylation profiling identifies hypermethylated biomarkers in high-grade cervical intraepithelial neoplasia

Epigenetic modifications, such as aberrant DNA promoter methylation, are frequently observed in cervical cancer. Identification of hypermethylated regions allowing discrimination between normal cervical epithelium and high-grade cervical intraepithelial neoplasia (CIN2/3), or worse, may improve current cervical cancer population-based screening programs. In this study, the DNA methylome of high-grade CIN lesions was studied using genome-wide DNA methylation screening to identify potential biomarkers for early diagnosis of cervical neoplasia. Methylated DNA Immunoprecipitation (MeDIP) combined with DNA microarray was used to compare DNA methylation profiles of epithelial cells derived from high-grade CIN lesions with normal cervical epithelium. Hypermethylated differentially methylated regions (DMRs) were identified. Validation of nine selected DMRs using BSP and MSP in cervical tissue revealed methylation in 63.2–94.7% high-grade CIN and in 59.3–100% cervical carcinomas. QMSP for the two most significant high-grade CIN-specific methylation markers was conducted exploring test performance in a large series of cervical scrapings. Frequency and relative level of methylation were significantly different between normal and cancer samples. Clinical validation of both markers in cervical scrapings from patients with an abnormal cervical smear confirmed that frequency and relative level of methylation were related with increasing severity of the underlying CIN lesion and that ROC analysis was discriminative. These markers represent the COL25A1 and KATNAL2 and their observed increased methylation upon progression could intimate the regulatory role in carcinogenesis. In conclusion, our newly identified hypermethylated DMRs represent specific DNA methylation patterns in high-grade CIN lesions and are candidate biomarkers for early detection.     

Application of a semipermeable surface column for the determination of amoxicillin in human blood serum

A high-performance liquid chromatography column-switching system for the automated determination of amoxicillin in human serum was developed as a more efficient alternative for the already existing systems with off-line sample pretreatment. The column-switching system consists of a semipermeable surface (SPS) column and an analytical reversed-phase (RP) C18 column. After centrifuging, pure serum samples were injected into the column-switching system. Clean-up, with regard to removal of proteins, was performed on the SPS column. The fraction containing amoxicillin was concentrated on the analytical RP-C18 column. Finally, chromatography and detection were performed with the RP-C18 column using UV detection at 234 nm. The total analysis time was 15 min. The method has proven to be reliable and to be more time- and resource-efficient compared to previously used methods with off-line sample clean-up. It is now used in bioavailability studies for the development of new amoxicillin formulations.     

DIATOM SILICA BIOMINERALIZATION: AT NANOSCALE LEVEL A CHEMICALLY UNIFORM PROCESS

Using a high-brilliance synchrotron X-ray source, combined small- and wide-angle X-ray scattering (SAXS and WAXS) was applied to study nanoscale characteristics, in particular pore size in the range of 3 to 65 nm, of a variety of unialgal cultures of centric and pennate diatoms, and of mixed diatom populations sampled in the field. Results of scattering analysis were compared with details of pore size, structure and orientation visible at the electron microscopic level. WAXS patterns did not reveal any crystalline phase or features of microcrystallinity (resolution 0.07 to 0.51 nm), which implies a totally amorphous character of the SiO₂ matrix of the frustule material. SAXS data (resolution 3 to 65 nm) provided information on geometry, size, and distribution of pores in the silica. Overall, two pore regions were recognized that were common to the silica of all samples: the smallest (d less than 10 nm) regularly spaced and shaped spherically, the larger (up to 65 nm) being cylinders or slits. Apparently, at a nanoscale level diatomaceous silica is quite homologous among species, in agreement with the chemical principles of silica polymerization under the conditions of pH and precursor concentrations inside the silicon deposition vesicle. The final frustule "macro"-morphology is of course species-specific, being determined genetically. Synthetically-derived MCM-type silicas have a similarly organized pore distribution in an amorphous silica matrix as we found in all diatom species studied. We therefore suggest that organic molecules of a kind used as structure-directing agents to produce these artificial silicas play a role in the nucleation of the silica polymerization reaction and the shaping of pore morphology inside the silicon deposition vesicle of diatoms. Structure-directing molecules now await isolation from the SDV, followed by identification and characterisation by molecular techniques.