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Data-Driven Modeling of Intracellular Auxin Fluxes Indicates a Dominant Role of the ER in Controlling Nuclear Auxin Uptake
Middleton, Alistair M. ; Bosco, Cristina Dal; Chlap, Phillip ; Bensch, Robert ; Harz, Hartmann ; Ren, Fugang ; Bergmann, Stefan ; Wend, Sabrina ; Weber, Wilfried ; Hayashi, Ken Ichiro ; Zurbriggen, Matias D. ; Uhl, Rainer ; Ronneberger, Olaf ; Palme, Klaus ; Fleck, Christian ; Dovzhenko, Alexander - \ 2018
Cell Reports 22 (2018)11. - ISSN 2211-1247 - p. 3044 - 3057.
auxin - auxin flux - auxin sensor - endoplasmic reticulum - fluorescent aux - mathematical modeling - microscopy - nucleus - protoplasts - single cells
In plants, the phytohormone auxin acts as a master regulator of developmental processes and environmental responses. The best characterized process in the auxin regulatory network occurs at the subcellular scale, wherein auxin mediates signal transduction into transcriptional programs by triggering the degradation of Aux/IAA transcriptional repressor proteins in the nucleus. However, whether and how auxin movement between the nucleus and the surrounding compartments is regulated remain elusive. Using a fluorescent auxin analog, we show that its diffusion into the nucleus is restricted. By combining mathematical modeling with time course assays on auxin-mediated nuclear signaling and quantitative phenotyping in single plant cell systems, we show that ER-to-nucleus auxin flux represents a major subcellular pathway to directly control nuclear auxin levels. Our findings propose that the homeostatically regulated auxin pool in the ER and ER-to-nucleus auxin fluxes underpin auxin-mediated downstream responses in plant cells. Middleton et al. study how the plant phytohormone auxin enters the nucleus by using quantitative phenotyping in single plant cell systems and bespoke mathematical models that relate controlled perturbations to experimentally measurable responses. Their findings show that auxin predominantly enters the nucleus via the endoplasmic reticulum.
High Rate Biomethanation of Carbon Monoxide-Rich Gases via a Thermophilic Synthetic Coculture
Diender, Martijn ; Uhl, Philipp S. ; Bitter, Johannes H. ; Stams, Alfons J.M. ; Sousa, Diana Z. - \ 2018
ACS sustainable chemistry & engineering 6 (2018)2. - ISSN 2168-0485 - p. 2169 - 2176.
Carbon monoxide-fermenting microorganisms can be used for the production of a wide range of commodity chemicals and fuels from syngas (generated by gasification of, e.g., wastes or biomass) or industrial off-gases (e.g., from steel industry). Microorganisms are normally more resistant to contaminants in the gas (e.g., hydrogen sulfide) than chemical catalysts, less expensive and self-regenerating. However, some carboxydotrophs are sensitive to high concentrations of CO, resulting in low growth rates and productivities. We hypothesize that cultivation of synthetic cocultures can be used to improve overall rates of CO bioconversion. As a case study, a thermophilic microbial coculture, consisting of Carboxydothermus hydrogenoformans and Methanothermobacter thermoautotrophicus was constructed to study the effect of cocultivation on conversion of CO-rich gases to methane. In contrast to the methanogenic monoculture, the coculture was able to efficiently utilize CO or mixtures of H2/CO/CO2 to produce methane at high efficiency and high rates. In CSTR-bioreactors operated in continuous mode, the coculture converted artificial syngas (66.6% H2:33.3% CO) to an outflow gas with a methane content of 72%, approaching the 75% theoretical maximum. CO conversion efficiencies of 93% and volumetric production rates of 4 m3methane/m3liquid/day were achieved. This case shows that microbial cocultivation can result in a significant improvement of gas-fermentation of CO-rich gases.
Attachment of antimicrobial peptides to reverse osmosis membranes by Cu(i)-catalyzed 1,3-dipolar alkyne-azide cycloaddition
Bodner, Elias J. ; Kandiyote, Nitzan Shtreimer ; Lutskiy, Marina Yamit ; Albada, Bauke ; Metzler-Nolte, Nils ; Uhl, Wolfgang ; Kasher, Roni ; Arnusch, Christopher J. - \ 2016
RSC Advances : An international journal to further the chemical sciences 6 (2016)94. - ISSN 2046-2069 - p. 91815 - 91823.
Biofilms are detrimental to many industrial systems that include reverse osmosis (RO) membranes. Accordingly, the development of surfaces with inherently bactericidal properties has attracted much research attention. Antimicrobial peptides (AMPs) have been shown to be potent antimicrobial and anti-biofilm agents. In the current study, we developed an efficient synthetic procedure for AMP immobilization on RO membranes which is based on the copper(i) mediated Huisgen 1,3-dipolar cycloaddition reaction ("click chemistry"). Optimization of the reaction temperature, time, peptide and catalyst concentration resulted in efficient coupling of peptides to the membrane surface. The reaction conditions did not affect membrane salt rejection, and resulted in only a slight reduction (14%) in pure water flux at the highest temperature tested (80 °C). Short AMPs that consisted of Arg-Trp repeats were attached onto a virgin RO membrane surface, and an RO membrane surface coated with a copolymer of methacrylic acid and poly(ethylene glycol)methacrylate. In a bacterial contact killing assay, the resulting peptide-modified membrane surfaces showed increased antimicrobial activity especially on the virgin membrane as compared to unmodified membranes. This study provides a basis for further research into the attachment of a wide variety of antimicrobials or other entities to surfaces.
Chemoprevention of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ)-induced colonic and hepatic preneoplastic lesions in the F344 rat by cruciferous vegetables administered simultaneously with the carcinogen
Kassie, F. ; Uhl, M. ; Grasl-Kraupp, B. ; Verkerk, R. ; Kundi, M. ; Chabicovsky, M. ; Schulte-Hermann, R. ; Knasmüller, S. - \ 2003
Carcinogenesis 24 (2003)2. - ISSN 0143-3334 - p. 255 - 261.
aberrant crypt foci - performance liquid-chromatography - n-nitrosodimethylamine - epidemiologic evidence - quantitative-analysis - breakdown products - solvent extracts - murine colon - inhibition - apoptosis
The aim of this study was to investigate the chemopreventive effects of widely consumed cruciferous vegetables, namely Brussels sprouts and red cabbage towards 2-amino3-methylimidazo[4,5-f]quinoline (IQ)-induced preneoplastic lesions [liver glutathione-S-transferase placental positive (GST-P+) foci and colonic aberrant crypt foci (ACF)]. Male F344 rats were treated with IQ (100 mg/kg bw/g) on 10 alternating days and received drinking water supplemented with Brussels sprouts and red cabbage juices (5% v/v) before and during the carcinogen treatment. From each vegetable two different cultivars were tested. Brussels sprouts reduced the frequency of IQ-induced aberrant foci in both organs (41-52% in the colon and 27-67% in the liver). Also, Brussels sprouts drastically diminished (85-91%) the size of liver GST-P+ foci, but no such effect was seen in the colon. With red cabbage, the size of liver GST-P+ foci was markedly reduced (41-83%) whereas the foci frequency was only moderately decreased (19-50%). No protection was seen in the colon after treatment with red cabbage. Cooking (10 min, 100degreesC) of the vegetables had no influence on their protective effects. The stronger chemoprotective effects of Brussels sprouts may be due to the fact that the overall glucosinolate contents were substantially (2-3-fold) higher than those of the cabbage cultivars, but it was not possible to attribute the reduction of preneoplastic lesions to specific glucosinolates. The activities of hepatic UDP-glucuronosyltransferase form 2 (UDPGT-2) and cytochrome P4501A2 were increased by both vegetables. The induction effect of Brussels sprouts on the activity of UDPGT-2 was more marked than that of the red cabbage cultivars, suggesting that increased glucuronidation of IQ may account for the reduction of the preneoplastic lesions. Our findings support the assumption that Brassica vegetables protect against the carcinogenic effects of heterocyclic amines.
Protective effects of Brussels sprouts towards B[a]P-induced DNA damage: a model study with the single-cell gel electrophpresis (SCGE)/Hep G2 assay
Laky, B. ; Knasmuller, S. ; Gminski, R. ; Mersch-Sundermann, V. ; Scharf, G. ; Verkerk, R. ; Freywald, C. ; Uhl, M. ; Kassie, F. - \ 2002
Food and Chemical Toxicology 40 (2002)8. - ISSN 0278-6915 - p. 1077 - 1083.
benzyl isothiocyanate - metabolizing enzymes - in-vitro - vegetables - glutathione - extracts - fruits - allyl
The aim of this study was to investigate the chemoprotective effects of Brussels sprouts juice towards benzo[a]pyrene (B(a)P)-induced DNA damage in the single-cell gel electrophoresis (SCGE)/Hep G2 test system. This assay combines the advantages of the SCGE assay with that of the use of human-derived cells possessing inducible phase I and phase 11 enzymes. Co-treatment of Hep G2 cells with small amounts of Brussels sprouts juice (0.25-2.0 mul/ml) and B(a)P reduced the genotoxic effect of the latter in a dose-dependent manner. Contrary to the results with the crude juice, unexpected synergistic effects were observed with allyl isothiocyanate (AITC, 1.0-6.0 muM), a breakdown product of sinigrin, which is the most abundant glucosinolate in Brussels sprouts. Although these concentrations of AITC did not cause DNA damage per se, at higher concentrations (greater than or equal to 25 muM), the compound caused a pronounced dose-dependent DNA damage by itself. Mechanistic studies showed that Brussels sprouts juice causes induction of activities of ethoxyresorufin O-deethylase (EROD) and glutathione S-transferase (GST) at dose levels which were protective towards B(a)P. In combined treatment experiments with (+/-)-anti-benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE, 5.0 muM), the main genotoxic metabolite of B(a)P, and Brussels sprouts juice, only weak protection was found indicating that the mechanism of chemoprotection of Brussels sprouts is not mediated through inactivation of this metabolite. In conclusion, our findings show that Brussels sprouts are highly protective against B(a)P-induced DNA damage in human-derived cells. (C) 2002 Elsevier Science Ltd. All rights reserved.