TY - JOUR A1 - Muñoz, Alfonso A1 - Mangano, Silvina A1 - Paz Gonzalez-Garcia, Mary A1 - Contreras, Ramon A1 - Sauer, Michael A1 - De Rybel, Bert A1 - Weijers, Dolf A1 - Juan Sanchez-Serrano, Jose A1 - Sanmartin, Maite A1 - Rojo, Enrique T1 - RIMA-Dependent Nuclear Accumulation of IYO Triggers Auxin-Irreversible Cell Differentiation in Arabidopsis JF - The plant cell N2 - The transcriptional regulator MINIYO (IYO) is essential and rate-limiting for initiating cell differentiation in Arabidopsis thaliana. Moreover, IYO moves from the cytosol into the nucleus in cells at the meristem periphery, possibly triggering their differentiation. However, the genetic mechanisms controlling IYO nuclear accumulation were unknown, and the evidence that increased nuclear IYO levels trigger differentiation remained correlative. Searching for IYO interactors, we identified RPAP2 IYO Mate (RIMA), a homolog of yeast and human proteins linked to nuclear import of selective cargo. Knockdown of RIMA causes delayed onset of cell differentiation, phenocopying the effects of IYO knockdown at the transcriptomic and developmental levels. Moreover, differentiation is completely blocked when IYO and RIMA activities are simultaneously reduced and is synergistically accelerated when IYO and RIMA are concurrently overexpressed, confirming their functional interaction. Indeed, RIMA knockdown reduces the nuclear levels of IYO and prevents its prodifferentiation activity, supporting the conclusion that RIMA-dependent nuclear IYO accumulation triggers cell differentiation in Arabidopsis. Importantly, by analyzing the effect of the IYO/RIMA pathway on xylem pole pericycle cells, we provide compelling evidence reinforcing the view that the capacity for de novo organogenesis and regeneration from mature plant tissues can reside in stem cell reservoirs. Y1 - 0201 U6 - https://doi.org/10.1105/tpc.16.00791 SN - 1040-4651 SN - 1532-298X VL - 29 IS - 3 SP - 575 EP - 588 PB - American Society of Plant Physiologists CY - Rockville ER - TY - JOUR A1 - Skłodowski, Kamil A1 - Riedelsberger, Janin A1 - Raddatz, Natalia A1 - Riadi, Gonzalo A1 - Caballero, Julio A1 - Chérel, Isabelle A1 - Schulze, Waltraud A1 - Graf, Alexander A1 - Dreyer, Ingo T1 - The receptor-like pseudokinase MRH1 interacts with the voltage-gated potassium channel AKT2 JF - Scientific reports N2 - The potassium channel AKT2 plays important roles in phloem loading and unloading. It can operate as inward-rectifying channel that allows H+-ATPase-energized K+ uptake. Moreover, through reversible post-translational modifications it can also function as an open, K+-selective channel, which taps a ‘potassium battery’, providing additional energy for transmembrane transport processes. Knowledge about proteins involved in the regulation of the operational mode of AKT2 is very limited. Here, we employed a large-scale yeast two-hybrid screen in combination with fluorescence tagging and null-allele mutant phenotype analysis and identified the plasma membrane localized receptor-like kinase MRH1/MDIS2 (AT4G18640) as interaction partner of AKT2. The phenotype of the mrh1-1 knockout plant mirrors that of akt2 knockout plants in energy limiting conditions. Electrophysiological analyses showed that MRH1/MDIS2 failed to exert any functional regulation on AKT2. Using structural protein modeling approaches, we instead gathered evidence that the putative kinase domain of MRH1/MDIS2 lacks essential sites that are indispensable for a functional kinase suggesting that MRH1/MDIS2 is a pseudokinase. We propose that MRH1/MDIS2 and AKT2 are likely parts of a bigger protein complex. MRH1 might help to recruit other, so far unknown partners, which post-translationally regulate AKT2. Additionally, MRH1 might be involved in the recognition of chemical signals. Y1 - 2017 U6 - https://doi.org/10.1038/srep44611 SN - 2045-2322 VL - 7 PB - Nature Publishing Group CY - London ER - TY - JOUR A1 - Mohandesan, Elmira A1 - Speller, Camilla F. A1 - Peters, Joris A1 - Uerpmann, Hans-Peter A1 - Uerpmann, Margarethe A1 - De Cupere, Bea A1 - Hofreiter, Michael A1 - Burger, Pamela A. T1 - Combined hybridization capture and shotgun sequencing for ancient DNA analysis of extinct wild and domestic dromedary camel JF - Molecular ecology resources N2 - The performance of hybridization capture combined with next-generation sequencing (NGS) has seen limited investigation with samples from hot and arid regions until now. We applied hybridization capture and shotgun sequencing to recover DNA sequences from bone specimens of ancient-domestic dromedary (Camelus dromedarius) and its extinct ancestor, the wild dromedary from Jordan, Syria, Turkey and the Arabian Peninsula, respectively. Our results show that hybridization capture increased the percentage of mitochondrial DNA (mtDNA) recovery by an average 187-fold and in some cases yielded virtually complete mitochondrial (mt) genomes at multifold coverage in a single capture experiment. Furthermore, we tested the effect of hybridization temperature and time by using a touchdown approach on a limited number of samples. We observed no significant difference in the number of unique dromedary mtDNA reads retrieved with the standard capture compared to the touchdown method. In total, we obtained 14 partial mitochondrial genomes from ancient-domestic dromedaries with 17-95% length coverage and 1.27-47.1-fold read depths for the covered regions. Using whole-genome shotgun sequencing, we successfully recovered endogenous dromedary nuclear DNA (nuDNA) from domestic and wild dromedary specimens with 1-1.06-fold read depths for covered regions. Our results highlight that despite recent methodological advances, obtaining ancient DNA (aDNA) from specimens recovered from hot, arid environments is still problematic. Hybridization protocols require specific optimization, and samples at the limit of DNA preservation need multiple replications of DNA extraction and hybridization capture as has been shown previously for Middle Pleistocene specimens. KW - ancient DNA KW - Camelus dromedarius KW - capture enrichment KW - degraded DNA KW - mitochondrial genome (mtDNA) KW - next-generation sequencing Y1 - 2017 U6 - https://doi.org/10.1111/1755-0998.12551 SN - 1755-098X SN - 1755-0998 VL - 17 IS - 2 SP - 300 EP - 313 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Braig, Friederike A1 - Kriegs, Malte A1 - Voigtlaender, Minna A1 - Habel, Beate A1 - Grob, Tobias A1 - Biskup, Karina A1 - Blanchard, Veronique A1 - Sack, Markus A1 - Thalhammer, Anja A1 - Ben Batalla, Isabel A1 - Braren, Ingke A1 - Laban, Simon A1 - Danielczyk, Antje A1 - Goletz, Steffen A1 - Jakubowicz, Elzbieta A1 - Maerkl, Bruno A1 - Trepel, Martin A1 - Knecht, Rainald A1 - Riecken, Kristoffer A1 - Fehse, Boris A1 - Loges, Sonja A1 - Bokemeyer, Carsten A1 - Binder, Mascha T1 - Cetuximab Resistance in Head and Neck Cancer Is Mediated by EGFR-K-521 Polymorphism JF - Cancer research N2 - Head and neck squamous cell carcinomas (HNSCC) exhibiting resistance to the EGFR-targeting drug cetuximab poses a challenge to their effective clinical management. Here, we report a specific mechanism of resistance in this setting based upon the presence of a single nucleotide polymorphism encoding EGFR-K-521 (K-allele), which is expressed in > 40% of HNSCC cases. Patients expressing the K-allele showed significantly shorter progressionfree survival upon palliative treatment with cetuximab plus chemotherapy or radiation. In several EGFR-mediated cancer models, cetuximab failed to inhibit downstream signaling or to kill cells harboring a high K-allele frequency. Cetuximab affinity for EGFR-K-521 was reduced slightly, but ligand-mediated EGFR acti-vation was intact. We found a lack of glycan sialyation on EGFR-K-521 that associated with reduced protein stability, suggesting a structural basis for reduced cetuximab efficacy. CetuGEX, an antibody with optimized Fc glycosylation targeting the same epitope as cetuximab, restored HNSCC sensitivity in a manner associated with antibody-dependent cellular cytotoxicity rather than EGFR pathway inhibition. Overall, our results highlight EGFR-K-521 expression as a key mechanism of cetuximab resistance to evaluate prospectively as a predictive biomarker in HNSCC patients. Further, they offer a preclinical rationale for the use of ADCC-optimized antibodies to treat tumors harboring this EGFR isoform. Y1 - 2017 U6 - https://doi.org/10.1158/0008-5472.CAN-16-0754 SN - 0008-5472 SN - 1538-7445 VL - 77 IS - 5 SP - 1188 EP - 1199 PB - American Association for Cancer Research CY - Philadelphia ER - TY - JOUR A1 - Valente, Luis A1 - Etienne, Rampal S. A1 - Davalos, Liliana M. T1 - Recent extinctions disturb path to equilibrium diversity in Caribbean bats JF - Nature Ecology & Evolution N2 - Islands are ideal systems to model temporal changes in biodiversity and reveal the influence of humans on natural communities. Although theory predicts biodiversity on islands tends towards an equilibrium value, the recent extinction of large proportions of island biotas complicates testing this model. The well-preserved subfossil record of Caribbean bats-involving multiple insular radiations-provides a rare opportunity to model diversity dynamics in an insular community. Here, we reconstruct the diversity trajectory in noctilionoid bats of the Greater Antilles by applying a dynamic model of colonization, extinction and speciation to phylogenetic and palaeontological data including all known extinct and extant species. We show species richness asymptotes to an equilibrium value, a demonstration of natural equilibrium dynamics across an entire community. However, recent extinctions-many caused by humans-have wiped out nearly a third of island lineages, dragging diversity away from equilibrium. Using a metric to measure island biodiversity loss, we estimate it will take at least eight million years to regain pre-human diversity levels. Our integrative approach reveals how anthropogenic extinctions can drastically alter the natural trajectory of biological communities, resulting in evolutionary disequilibrium. Y1 - 2017 U6 - https://doi.org/10.1038/s41559-016-0026 SN - 2397-334X VL - 1 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Kolk, Jens A1 - Naaf, Tobias A1 - Wulf, Monika T1 - Paying the colonization credit BT - converging plant species richness in ancient and post-agricultural forests in NE Germany over five decades JF - Biodiversity and conservation N2 - Massive historical land cover changes in the Central European lowlands have resulted in a forest distribution that now comprises small remnants of ancient forests and more recently established post-agricultural forests. Here, land-use history is considered a key driver of recent herb-layer community changes, where an extinction debt in ancient forest remnants and/or a colonization credit in post-agricultural forests are being paid over time. On a regional scale, these payments should in theory lead toward a convergence in species richness between ancient and post-agricultural forests over time. In this study, we tested this assumption with a resurvey of 117 semi-permanent plots in the well-studied deciduous forests of the Prignitz region (Brandenburg, NE Germany), where we knew that the plant communities of post-agricultural stands exhibit a colonization credit while the extinction debt in ancient stands has largely been paid. We compared changes in the species richness of all herb layer species, forest specialists and ancient forest indicator species between ancient and post-agricultural stands with linear mixed effect models and determined the influence of patch connectivity on the magnitude of species richness changes. Species richness increased overall, but the richness of forest specialists increased significantly more in post-agricultural stands and was positively influenced by higher patch connectivity, indicating a convergence in species richness between the ancient and postagricultural stands. Furthermore, the richness of ancient forest indicator species only increased significantly in post-agricultural stands. For the first time, we were able to verify a gradual payment of the colonization credit in post-agricultural forest stands using a comparison of actual changes in temporal species richness. KW - Herb layer KW - Land-use history KW - Land-use legacy KW - Long-term change KW - Resurvey KW - Temperate forest Y1 - 2016 U6 - https://doi.org/10.1007/s10531-016-1271-y SN - 0960-3115 SN - 1572-9710 VL - 26 SP - 735 EP - 755 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Reschke, Stefan A1 - Mebs, Stefan A1 - Sigfridsson-Clauss, Kajsa G. V. A1 - Kositzki, Ramona A1 - Leimkühler, Silke A1 - Haumann, Michael T1 - Protonation and Sulfido versus Oxo Ligation Changes at the Molybdenum Cofactor in Xanthine Dehydrogenase (XDH) Variants Studied by X-ray Absorption Spectroscopy JF - Inorganic chemistry N2 - Enzymes of the xanthine oxidase family are among the best characterized mononuclear molybdenum enzymes. Open questions about their mechanism of transfer of an oxygen atom to the substrate remain. The enzymes share a molybdenum cofactor (Moco) with the metal ion binding a molybdopterin (MPT) molecule via its dithiolene function and terminal sulfur and oxygen groups. For xanthine dehydrogenase (XDH) from the bacterium Rhodobacter capsulatus, we used X-ray absorption spectroscopy to determine the Mo site structure, its changes in a pH range of 5-10, and the influence of amino acids (Glu730 and Gln179) close to Moco in wild-type (WT), Q179A, and E730A variants, complemented by enzyme kinetics and quantum chemical studies. Oxidized WT and Q179A revealed a similar Mo (VI) ion with each one MPT, Mo=O, Mo-O-, and Mo=S ligand, and a weak Mo-O(E730) bond at alkaline pH. Protonation of an oxo to a hydroxo (OH) ligand (pK similar to 6.8) causes inhibition of XDH at acidic pH, whereas deprotonated xanthine (pK similar to 8.8) is an inhibitor at alkaline pH. A similar acidic pK for the WT and Q179A. variants, as well as the metrical parameters of the Mo site and density functional theory calculations, suggested protonation at the equatorial oxo group. The sulfido was replaced with an oxo ligand in the inactive E730A variant, further showing another oxo and one Mo OH ligand at Mo, which are independent of pH. Our findings suggest a reaction mechanism for XDH in which an initial oxo rather than a hydroxo group and the sulfido ligand are essential for xanthine oxidation. Y1 - 2017 U6 - https://doi.org/10.1021/acs.inorgchem.6b02846 SN - 0020-1669 SN - 1520-510X VL - 56 IS - 4 SP - 2165 EP - 2176 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Hahn, Marc Benjamin A1 - Meyer, Susann A1 - Schröter, Maria-Astrid A1 - Seitz, Harald A1 - Kunte, Hans-Jörg A1 - Solomun, Tihomir A1 - Sturm, Heinz T1 - Direct electron irradiation of DNA in a fully aqueous environment BT - Damage determination in combination with Monte Carlo simulations JF - Physical chemistry, chemical physics : PCCP ; a journal of European chemical societies N2 - We report on a study in which plasmid DNA in water was irradiated with 30 keV electrons generated by a scanning electron microscope and passed through a 100 nm thick Si3N4 membrane. The corresponding Monte Carlo simulations suggest that the kinetic energy spectrum of the electrons throughout the water is dominated by low energy electrons (<100 eV). The DNA radiation damage, single-strand breaks (SSBs) and double-strand breaks (DSBs), was determined by gel electrophoresis. The median lethal dose of D-1/2 = 1.7 +/- 0.3 Gy was found to be much smaller as compared to partially or fully hydrated DNA irradiated under vacuum conditions. The ratio of the DSBs to SSBs was found to be 1 : 12 as compared to 1 : 88 found for hydrated DNA. Our method enables quantitative measurements of radiation damage to biomolecules (DNA, proteins) in solutions under varying conditions (pH, salinity, co-solutes) for an electron energy range which is difficult to probe by standard methods. Y1 - 2016 U6 - https://doi.org/10.1039/c6cp07707b SN - 1463-9076 SN - 1463-9084 VL - 19 IS - 3 SP - 1798 EP - 1805 PB - RSC Publ. CY - Cambridge ER - TY - JOUR A1 - Riedel, M. A1 - Sabir, N. A1 - Scheller, Frieder W. A1 - Parak, Wolfgang J. A1 - Lisdat, Fred T1 - Connecting quantum dots with enzymes BT - mediator-based approaches for the light-directed read-out of glucose and fructose oxidation JF - Nanoscale N2 - The combination of the biocatalytic features of enzymes with the unique physical properties of nanoparticles in a biohybrid system provides a promising approach for the development of advanced bioelectrocatalytic devices. This study describes the construction of photoelectrochemical signal chains based on CdSe/ZnS quantum dot (QD) modified gold electrodes as light switchable elements, and low molecular weight redox molecules for the combination with different biocatalysts. Photoelectrochemical and photoluminescence experiments verify that electron transfer can be achieved between the redox molecules hexacyanoferrate and ferrocene, and the QDs under illumination. Since for both redox mediators a concentration dependent photocurrent change has been found, light switchable enzymatic signal chains are built up with fructose dehydrogenase (FDH) and pyrroloquinoline quinone-dependent glucose dehydrogenase ((PQQ) GDH) for the detection of sugars. After immobilization of the enzymes at the QD electrode the biocatalytic oxidation of the substrates can be followed by conversion of the redox mediator in solution and subsequent detection at the QD electrode. Furthermore, (PQQ) GDH has been assembled together with ferrocenecarboxylic acid on top of the QD electrode for the construction of a funtional biohybrid architecture, showing that electron transfer can be realized from the enzyme over the redox mediator to the QDs and subsequently to the electrode in a completely immobilized fashion. The results obtained here do not only provide the basis for light-switchable biosensing and bioelectrocatalytic applications, but may also open the way for self-driven point-of-care systems by combination with solar cell approaches (power generation at the QD electrode by enzymatic substrate consumption). Y1 - 2017 U6 - https://doi.org/10.1039/c7nr00091j SN - 2040-3364 SN - 2040-3372 VL - 9 SP - 2814 EP - 2823 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Simons, Nadja K. A1 - Lewinsohn, Thomas A1 - Bluethgen, Nico A1 - Buscot, Francois A1 - Boch, Steffen A1 - Daniel, Rolf A1 - Gossner, Martin M. A1 - Jung, Kirsten A1 - Kaiser, Kristin A1 - Müller, Jörg A1 - Prati, Daniel A1 - Renner, Swen C. A1 - Socher, Stephanie A. A1 - Sonnemann, Ilja A1 - Weiner, Christiane N. A1 - Werner, Michael A1 - Wubet, Tesfaye A1 - Wurst, Susanne A1 - Weisser, Wolfgang W. T1 - Contrasting effects of grassland management modes on species-abundance distributions of multiple groups JF - Agriculture, ecosystems & environment : an international journal for scientific research on the relationship of agriculture and food production to the biosphere N2 - Intensive land use is a major cause of biodiversity loss, but most studies comparing the response of multiple taxa rely on simple diversity measures while analyses of other community attributes are only recently gaining attention. Species-abundance distributions (SADs) are a community attribute that can be used to study changes in the overall abundance structure of species groups, and whether these changes are driven by abundant or rare species. We evaluated the effect of grassland management intensity for three land-use modes (fertilization, mowing, grazing) and their combination on species richness and SADs for three belowground (arbuscular mycorrhizal fungi, prokaryotes and insect larvae) and seven aboveground groups (vascular plants, bryophytes and lichens; arthropod herbivores; arthropod pollinators; bats and birds). Three descriptors of SADs were evaluated: general shape (abundance decay rate), proportion of rare species (rarity) and proportional abundance of the commonest species (dominance). Across groups, taxonomic richness was largely unaffected by land-use intensity and only decreased with increasing mowing intensity. Of the three SAD descriptors, abundance decay rate became steeper with increasing combined land-use intensity across groups. This reflected a decrease in rarity among plants, herbivores and vertebrates. Effects of fertilization on the three descriptors were similar to the combined land-use intensity effects. Mowing intensity only affected the SAD descriptors of insect larvae and vertebrates, while grazing intensity produced a range of effects on different descriptors in distinct groups. Overall, belowground groups had more even abundance distribtitions than aboveground groups. Strong differences among aboveground groups and between above- and belowground groups indicate that no single taxonomic group can serve as an indicator for effects in other groups. In the past, the use of SADs has been hampered by concerns over theoretical models underlying specific forms of SADs. Our study shows that SAD descriptors that are not connected to a particular model are suitable to assess the effect of land use on community structure. KW - Biodiversity KW - Cutting frequency KW - Management intensity KW - Rank-abundance KW - Species loss KW - Rarity Y1 - 2017 U6 - https://doi.org/10.1016/j.agee.2016.12.022 SN - 0167-8809 SN - 1873-2305 VL - 237 SP - 143 EP - 153 PB - Elsevier CY - Amsterdam ER -