TY - JOUR A1 - Üstün, Suayib A1 - Bartetzko, Verena A1 - Börnke, Frederik T1 - The Xanthomonas effector XopJ triggers a conditional hypersensitive response upon treatment of N. benthamiana leaves with salicylic acid JF - Frontiers in plant science N2 - XopJ is a Xanthomonas type III effector protein that promotes bacterial virulence on susceptible pepper plants through the inhibition of the host cell proteasome and a resultant suppression of salicylic acid (SA) - dependent defense responses. We show here that Nicotiana benthamiana leaves transiently expressing XopJ display hypersensitive response (HR) -like symptoms when exogenously treated with SA. This apparent avirulence function of XopJ was further dependent on effector myristoylation as well as on an intact catalytic triad, suggesting a requirement of its enzymatic activity for HR-like symptom elicitation. The ability of XopJ to cause a HR-like symptom development upon SA treatment was lost upon silencing of SGT1 and NDR1, respectively, but was independent of EDS1 silencing, suggesting that XopJ is recognized by an R protein of the CC-NBS-LRR class. Furthermore, silencing of NPR1 abolished the elicitation of HR-like symptoms in XopJ expressing leaves after SA application. Measurement of the proteasome activity indicated that proteasome inhibition by XopJ was alleviated in the presence of SA, an effect that was not observed in NPR1 silenced plants. Our results suggest that XopJ - triggered HR-like symptoms are closely related to the virulence function of the effector and that XopJ follows a two-signal model in order to elicit a response in the non-host plant N. benthamiana. KW - Xanthomonas KW - type-III effector KW - XopJ KW - avirulence KW - salicylic acid Y1 - 2015 U6 - https://doi.org/10.3389/fpls.2015.00599 SN - 1664-462X VL - 6 PB - Frontiers Research Foundation CY - Lausanne ER - TY - JOUR A1 - Zurell, Damaris A1 - Eggers, Ute A1 - Kaatz, Michael A1 - Rotics, Shay A1 - Sapir, Nir A1 - Wikelski, Martin A1 - Nathan, Ran A1 - Jeltsch, Florian T1 - Individual-based modelling of resource competition to predict density-dependent population dynamics: a case study with white storks JF - Oikos N2 - Density regulation influences population dynamics through its effects on demographic rates and consequently constitutes a key mechanism explaining the response of organisms to environmental changes. Yet, it is difficult to establish the exact form of density dependence from empirical data. Here, we developed an individual-based model to explore how resource limitation and behavioural processes determine the spatial structure of white stork Ciconia ciconia populations and regulate reproductive rates. We found that the form of density dependence differed considerably between landscapes with the same overall resource availability and between home range selection strategies, highlighting the importance of fine-scale resource distribution in interaction with behaviour. In accordance with theories of density dependence, breeding output generally decreased with density but this effect was highly variable and strongly affected by optimal foraging strategy, resource detection probability and colonial behaviour. Moreover, our results uncovered an overlooked consequence of density dependence by showing that high early nestling mortality in storks, assumed to be the outcome of harsh weather, may actually result from density dependent effects on food provision. Our findings emphasize that accounting for interactive effects of individual behaviour and local environmental factors is crucial for understanding density-dependent processes within spatially structured populations. Enhanced understanding of the ways animal populations are regulated in general, and how habitat conditions and behaviour may dictate spatial population structure and demographic rates is critically needed for predicting the dynamics of populations, communities and ecosystems under changing environmental conditions. Y1 - 2015 U6 - https://doi.org/10.1111/oik.01294 SN - 0030-1299 SN - 1600-0706 VL - 124 IS - 3 SP - 319 EP - 330 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Zhang, Houbin A1 - Hanke-Gogokhia, Christin A1 - Jiang, Li A1 - Li, Xiaobo A1 - Wang, Pu A1 - Gerstner, Cecilia D. A1 - Frederick, Jeanne M. A1 - Yang, Zhenglin A1 - Baehr, Wolfgang T1 - Mistrafficking of prenylated proteins causes retinitis pigmentosa 2 JF - The FASEB journal : the official journal of the Federation of American Societies for Experimental Biology N2 - The retinitis pigmentosa 2 polypeptide (RP2) functions as a GTPase-activating protein (GAP) for ARL3 (Arf-like protein 3), a small GTPase. ARL3 is an effector of phosphodiesterase 6 Delta (PDE6D), a prenyl-binding protein and chaperone of prenylated protein in photoreceptors. Mutations in the human RP2 gene cause X-linked retinitis pigmentosa (XLRP) and cone-rod dystrophy (XL-CORD). To study mechanisms causing XLRP, we generated an RP2 knockout mouse. The RP2h(-/-) mice exhibited a slowly progressing rod-cone dystrophy simulating the human disease. RP2h(-/-) scotopic a-wave and photopic b-wave amplitudes declined at 1 mo of age and continued to decline over the next 6 mo. Prenylated PDE6 subunits and G-protein coupled receptor kinase 1 (GRK1) were unable to traffic effectively to the RP2h(-/-) outer segments. Mechanistically, absence of RP2 GAP activity increases ARL3-GTP levels, forcing PDE6D to assume a predominantly "closed" conformation that impedes binding of lipids. Lack of interaction disrupts trafficking of PDE6 and GRK1 to their destination, the photoreceptor outer segments. We propose that hyperactivity of ARL3-GTP in RP2 knockout mice and human patients with RP2 null alleles leads to XLRP resembling recessive rod-cone dystrophy. KW - rod-cone dystrophy KW - ARL3 KW - PDE6D KW - RP2 KW - XLRP Y1 - 2015 U6 - https://doi.org/10.1096/fj.14-257915 SN - 0892-6638 SN - 1530-6860 VL - 29 IS - 3 SP - 932 EP - 942 PB - Federation of American Societies for Experimental Biology CY - Bethesda ER - TY - JOUR A1 - Zeng, Ting A1 - Pankratov, Dmitry A1 - Falk, Magnus A1 - Leimkühler, Silke A1 - Shleev, Sergey A1 - Wollenberger, Ursula T1 - Miniature direct electron transfer based sulphite/oxygen enzymatic fuel cells JF - Biosensors and bioelectronics : the principal international journal devoted to research, design development and application of biosensors and bioelectronics N2 - A direct electron transfer (DET) based sulphite/oxygen biofuel cell is reported that utilises human sulphite oxidase (hSOx) and Myrothecium verrucaria bilirubin oxidase (MvBOx) and nanostructured gold electrodes. For bioanode construction, the nanostructured gold microelectrodes were further modified with 3,3'-dithiodipropionic acid di(N-hydroxysuccinimide ester) to which polyethylene imine was covalently attached. hSOx was adsorbed onto this chemically modified nanostructured electrode with high surface loading of electroactive enzyme and in presence of sulphite high anodic bioelectrocatalytic currents were generated with an onset potential of 0.05 V vs. NHE. The biocathode contained MyBOx directly adsorbed to the deposited gold nanoparticles for cathodic oxygen reduction starting at 0.71 V vs. NHE. Both enzyme electrodes were integrated to a DET-type biofuel cell. Power densities of 8 and 1 mu W cm(-2) were achieved at 0.15 V and 0.45 V of cell voltages, respectively, with the membrane based biodevices under aerobic conditions. (C) 2014 Elsevier B.V. All rights reserved. KW - Enzymatic fuel cell KW - Microscale electrode KW - Direct electron transfer KW - Sulphite oxidase KW - Bilirubin oxidase Y1 - 2015 U6 - https://doi.org/10.1016/j.bios.2014.10.080 SN - 0956-5663 SN - 1873-4235 VL - 66 SP - 39 EP - 42 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Zeng, Ting A1 - Leimkühler, Silke A1 - Koetz, Joachim A1 - Wollenberger, Ursula T1 - Effective Electrochemistry of Human Sulfite Oxidase Immobilized on Quantum-Dots-Modified Indium Tin Oxide Electrode JF - ACS applied materials & interfaces N2 - The bioelectrocatalytic sulfite oxidation by human sulfite oxidase (hSO) on indium tin oxide (ITO) is reported, which is facilitated by functionalizing of the electrode surface with polyethylenimine (PEI)-entrapped CdS nanoparticles and enzyme. hSO was assembled onto the electrode with a high surface loading of electroactive enzyme. In the presence of sulfite but without additional mediators, a high bioelectrocatalytic current was generated. Reference experiments with only PEI showed direct electron transfer and catalytic activity of hSO, but these were less pronounced. The application of the polyelectrolyte-entrapped quantum dots (QDs) on ITO electrodes provides a compatible surface for enzyme binding with promotion of electron transfer. Variations of the buffer solution conditions, e.g., ionic strength, pH, viscosity, and the effect of oxygen, were studied in order to understand intramolecular and heterogeneous electron transfer from hSO to the electrode. The results are consistent with a model derived for the enzyme by using flash photolysis in solution and spectroelectrochemistry and molecular dynamic simulations of hSO on monolayer-modified gold electrodes. Moreover, for the first time a photoelectrochemical electrode involving immobilized hSO is demonstrated where photoexcitation of the CdS/hSO-modified electrode lead to an enhanced generation of bioelectrocatalytic currents upon sulfite addition. Oxidation starts already at the redox potential of the electron transfer domain of hSO and is greatly increased by application of a small overpotential to the CdS/hSO-modified ITO. KW - human sulfite oxidase KW - direct electrochemistry KW - bioelectrocatalysis KW - photocurrent KW - CdS quantum dots Y1 - 2015 U6 - https://doi.org/10.1021/acsami.5b06665 SN - 1944-8244 VL - 7 IS - 38 SP - 21487 EP - 21494 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Yildirim-Semerci, Cigdem A1 - Benayahu, Dafna A1 - Adamovski, Miriam A1 - Wollenberger, Ursula T1 - An Electrochemical Assay for Monitoring Differentiation of the Osteoblastic Cell Line (MBA-15) on the Sensor Chip JF - Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis N2 - An electrochemical assay for the indication of the activity of the cell bound differentiation marker alkaline phosphatase (ALP) is proposed using voltammetry on an in-vitro cell culture. The basis of the assay is cultivation of cells on gold microelectrodes in wells of a microplate, catalytic hydrolysis of p-aminophenyl phosphate by ALP and indication of p-aminophenol oxidation by square wave voltammetry (SWV) with the sensors onto which the cells attached. The morphology of the bone marrow stromal cell line (MBA-15) on the electrode surface was investigated and it exhibited in vitro osteogenic characteristics. Since ALP is expressed on the cell surface in early differentiation stage of osteoblastic cells, its activity was followed after different culture times over a period of 144 h by recording repetitive voltammograms at different time points upon addition of the substrate p-aminophenyl phosphate. The ALP activity was estimated from the signal increase related to formation rate of p-aminophenol and the number of cells. The highest value was measured at 120 h, when the cells reached confluence. The results of the electrochemical activity assay are consistent with the colorimetric acquired value from p-nitrophenol formation rate. KW - Alkaline phosphatase KW - Osteoblast KW - Voltammetry KW - Biomarker KW - p-Aminophenol Y1 - 2015 U6 - https://doi.org/10.1002/elan.201400684 SN - 1040-0397 SN - 1521-4109 VL - 27 IS - 6 SP - 1350 EP - 1358 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Weiß, Lina A1 - Jeltsch, Florian T1 - The response of simulated grassland communities to the cessation of grazing JF - Ecological modelling : international journal on ecological modelling and engineering and systems ecolog N2 - Changes in land-use are supposed to be among the severest prospective threats to plant diversity worldwide. In semi-natural temperate grasslands, the cessation of traditional land use like livestock grazing is considered to be one of the most important drivers of the diversity loss witnessed within the last decades. Despite of the enormous number of studies on successional pathways following grazing abandonment there is no general pattern of how grassland communities are affected in terms of diversity, trait composition and pace of succession. To gain a comprehensive picture is difficult given the heterogeneity of environments and the time and effort needed for long-term investigations. We here use a proven individual- and trait-based grassland community model to analyze short- and long-term consequences of grazing abandonment under different assumptions of resource availability, pre-abandonment grazing intensity and regional isolation of communities. Grazing abandonment led to a decrease of plant functional type (PFT) diversity in all but two scenarios in the long-term. In short-term we also found an increase or no change in Shannon diversity for several scenarios. With grazing abandonment we overall found an increase in maximum plant mass, clonal integration and longer lateral spread, a decrease in rosette plant types and in stress tolerant plants, as well as an increase in grazing tolerant and a decrease in grazing avoiding plant types. Observed changes were highly dependent on the regional configuration of communities, prevalent resource conditions and land use intensity before abandonment. While long-term changes took around 10-20 years in resource rich conditions, new equilibria established in resource poor conditions only after 30-40 years. Our results confirm the potential threats caused by recent land-use changes and the assumption that oligotrophic communities are more resistant than mesotrophic communities also for long-term abandonment. Moreover, results revealed that species-rich systems are not per se more resistant than species-poor grasslands. (C) 2015 Elsevier B.V. All rights reserved. KW - Diversity KW - Individual-based model KW - Land use intensity KW - Seed immigration KW - Abandonment KW - Resistance Y1 - 2015 U6 - https://doi.org/10.1016/j.ecolmodel.2015.02.002 SN - 0304-3800 SN - 1872-7026 VL - 303 SP - 1 EP - 11 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Weithoff, Guntram A1 - Rocha, Marcia R. A1 - Gaedke, Ursula T1 - Comparing seasonal dynamics of functional and taxonomic diversity reveals the driving forces underlying phytoplankton community structure JF - Freshwater biology N2 - In most biodiversity studies, taxonomic diversity is the measure for the multiplicity of species and is often considered to represent functional diversity. However, trends in taxonomic diversity and functional diversity may differ, for example, when many functionally similar but taxonomically different species co-occur in a community. The differences between these diversity measures are of particular interest in diversity research for understanding diversity patterns and their underlying mechanisms. We analysed a temporally highly resolved 20-year time series of lake phytoplankton to determine whether taxonomic diversity and functional diversity exhibit similar or contrasting seasonal patterns. We also calculated the functional mean of the community in n-dimensional trait space for each sampling day to gain further insights into the seasonal dynamics of the functional properties of the community. We found an overall weak positive relationship between taxonomic diversity and functional diversity with a distinct seasonal pattern. The two diversity measures showed synchronous behaviour from early spring to mid-summer and a more complex and diverging relationship from autumn to late winter. The functional mean of the community exhibited a recurrent annual pattern with the most prominent changes before and after the clear-water phase. From late autumn to winter, the functional mean of the community and functional diversity were relatively constant while taxonomic diversity declined, suggesting competitive exclusion during this period. A further decline in taxonomic diversity concomitant with increasing functional diversity in late winter to early spring is seen as a result of niche diversification together with competitive exclusion. Under these conditions, several different sets of traits are suitable to thrive, but within one set of functional traits only one, or very few, morphotypes can persist. Taxonomic diversity alone is a weak descriptor of trait diversity in phytoplankton. However, the combined analysis of taxonomic diversity and functional diversity, along with the functional mean of the community, allows for deeper insights into temporal patterns of community assembly and niche diversification. KW - algae KW - biodiversity KW - functional traits KW - seasonality KW - time series Y1 - 2015 U6 - https://doi.org/10.1111/fwb.12527 SN - 0046-5070 SN - 1365-2427 VL - 60 IS - 4 SP - 758 EP - 767 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Wannicke, Nicola A1 - Frindte, Katharina A1 - Gust, Giselher A1 - Liskow, Iris A1 - Wacker, Alexander A1 - Meyer, Andreas A1 - Grossart, Hans-Peter T1 - Measuring bacterial activity and community composition at high hydrostatic pressure using a novel experimental approach: a pilot study JF - FEMS microbiology ecology N2 - In this pilot study, we describe a high-pressure incubation system allowing multiple subsampling of a pressurized culture without decompression. The system was tested using one piezophilic (Photobacterium profundum), one piezotolerant (Colwellia maris) bacterial strain and a decompressed sample from the Mediterranean deep sea (3044 m) determining bacterial community composition, protein production (BPP) and cell multiplication rates (BCM) up to 27 MPa. The results showed elevation of BPP at high pressure was by a factor of 1.5 +/- 1.4 and 3.9 +/- 2.3 for P. profundum and C. maris, respectively, compared to ambient-pressure treatments and by a factor of 6.9 +/- 3.8 fold in the field samples. In P. profundum and C. maris, BCM at high pressure was elevated (3.1 +/- 1.5 and 2.9 +/- 1.7 fold, respectively) compared to the ambient-pressure treatments. After 3 days of incubation at 27 MPa, the natural bacterial deep-sea community was dominated by one phylum of the genus Exiguobacterium, indicating the rapid selection of piezotolerant bacteria. In future studies, our novel incubation system could be part of an isopiestic pressure chain, allowing more accurate measurement of bacterial activity rates which is important both for modeling and for predicting the efficiency of the oceanic carbon pump. KW - hydrostatic pressure KW - pressure chamber KW - piezophilic bacteria KW - deep-sea bacterial community KW - bacterial production KW - stable isotopes KW - membrane fatty acids Y1 - 2015 U6 - https://doi.org/10.1093/femsec/fiv036 SN - 0168-6496 SN - 1574-6941 VL - 91 IS - 5 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Wang, Ting A1 - Tohge, Takayuki A1 - Ivakov, Alexander A1 - Müller-Röber, Bernd A1 - Fernie, Alisdair R. A1 - Mutwil, Marek A1 - Schippers, Jos H. M. A1 - Persson, Staffan T1 - Salt-Related MYB1 Coordinates Abscisic Acid Biosynthesis and Signaling during Salt Stress in Arabidopsis JF - Plant physiology : an international journal devoted to physiology, biochemistry, cellular and molecular biology, biophysics and environmental biology of plants N2 - Abiotic stresses, such as salinity, cause global yield loss of all major crop plants. Factors and mechanisms that can aid in plant breeding for salt stress tolerance are therefore of great importance for food and feed production. Here, we identified a MYB-like transcription factor, Salt-Related MYB1 (SRM1), that negatively affects Arabidopsis (Arabidopsis thaliana) seed germination under saline conditions by regulating the levels of the stress hormone abscisic acid (ABA). Accordingly, several ABA biosynthesis and signaling genes act directly downstream of SRM1, including SALT TOLERANT1/NINE-CIS-EPOXYCAROTENOID DIOXYGENASE3, RESPONSIVE TO DESICCATION26, and Arabidopsis NAC DOMAIN CONTAINING PROTEIN19. Furthermore, SRM1 impacts vegetative growth and leaf shape. We show that SRM1 is an important transcriptional regulator that directly targets ABA biosynthesis and signaling-related genes and therefore may be regarded as an important regulator of ABA-mediated salt stress tolerance. Y1 - 2015 U6 - https://doi.org/10.1104/pp.15.00962 SN - 0032-0889 SN - 1532-2548 VL - 169 IS - 2 SP - 1027 EP - + PB - American Society of Plant Physiologists CY - Rockville ER -