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161.
Hiroshi Ohshima Yumiko Yoshie Sebastien Auriol Isabelle Gilibert 《Free radical biology & medicine》1998,25(9):1057-1065
Antioxidant and pro-oxidant activities of flavonoids have been reported. We have studied the effects of 18 flavonoids and related phenolic compounds on DNA damage induced by nitric oxide (NO), peroxynitrite, and nitroxyl anion (NO−). Similarly to our previous findings with catecholamines and catechol-estrogens, DNA single-strand breakage was induced synergistically when pBR322 plasmid was incubated in the presence of an NO-releasing compound (diethylamine NONOate) and a flavonoid having an ortho-trihydroxyl group in either the B ring (e.g., epigallocatechin gallate) or the A ring (e.g., quercetagetin). Either NO or any of the above flavonoids alone did not induce strand breakage significantly. However, most of the tested flavonoids inhibited the peroxynitrite-mediated formation of 8-nitroguanine in calf-thymus DNA, measured by a new HPLC-electrochemical detection method, as well as the peroxynitrite-induced strand breakage. NO− generated from Angeli’s salt caused DNA strand breakage, which was also inhibited by flavonoids but at only high concentrations. On the basis of these findings, we propose that NO− and/or peroxynitrite could be responsible for DNA strand breakage induced by NO and a flavonoid having an ortho-trihydroxyl group. Our results indicate that flavonoids have antioxidant properties, but some act as pro-oxidants in the presence of NO. 相似文献
162.
Maël Doré Keith Willmott Sebastien Lavergne Nicolas Chazot André V. L. Freitas Colin Fontaine Marianne Elias 《Ecology letters》2023,26(6):843-857
Understanding the mechanisms underlying species distributions and coexistence is both a priority and a challenge for biodiversity hotspots such as the Neotropics. Here, we highlight that Müllerian mimicry, where defended prey species display similar warning signals, is key to the maintenance of biodiversity in the c. 400 species of the Neotropical butterfly tribe Ithomiini (Nymphalidae: Danainae). We show that mimicry drives large-scale spatial association among phenotypically similar species, providing new empirical evidence for the validity of Müller's model at a macroecological scale. Additionally, we show that mimetic interactions drive the evolutionary convergence of species climatic niche, thereby strengthening the co-occurrence of co-mimetic species. This study provides new insights into the importance of mutualistic interactions in shaping both niche evolution and species assemblages at large spatial scales. Critically, in the context of climate change, our results highlight the vulnerability to extinction cascades of such adaptively assembled communities tied by positive interactions. 相似文献
163.
María Teresa Boquete Zulema Varela José Angel Fernández Juan Antonio Calleja Cristina Branquinho Antonina Chilà Nils Cronberg Ricardo Cruz de Carvalho Cristiana Aleixo Belén Estébanez‐Pérez Verónica Fernández‐González rés Baselga Carola Gómez‐Rodríguez Juana María González‐Mancebo Sebastien Leblond Javier Martínez‐Abaigar Nagore G. Medina Encarnación Núñez‐Olivera Jairo Patiño Rubén Retuerto Antón Vázquez‐Arias Alain Vanderpoorten Harald G. Zechmeister Jesús Ramón Aboal 《植物分类学报:英文版》2023,61(1):213-226
Unisexual bryophytes provide excellent models to study the mechanisms that regulate the frequency of sexual versusasexual reproduction in plants, and their ecological and evolutionary implications. Here, we determined sex expression, phenotypic sex ratio, and individual shoot traits in 242 populations of the cosmopolitan moss Pseudoscleropodium purum spanning its whole distributional range. We tested whether niche differentiation, sex-specific differences in shoot size, and biogeographical history explained the spatial variation of reproductive traits. We observed high levels of sex expression and predominantly female-biased populations, although both traits showed high intraspecific variation among populations. Sex expression and sex ratio were partly explained by current macroscale environmental variation, with male shoots being less frequent at the higher end of the environmental gradients defined by the current distribution of the species. Female bias in population sex ratio was significantly lower in areas recolonized after the last glacial maximum (recent populations) than in glacial refugia (long-term persistent populations). We demonstrated that reproductive trait variation in perennial unisexual mosses is partially driven by macroscale and historical environmental variation. Based on our results, we hypothesize that sexual dimorphism in environmental tolerance and vegetative growth contribute to sex ratio bias over time, constraining the chances of sexual reproduction, especially in long-term persistent populations. Further studies combining genetic analyses and population monitoring should improve our understanding of the implications of the intraspecific variation in the frequency of sexual versusasexual reproduction in bryophyte population fitness and eco-evolutionary dynamics. 相似文献
164.
Coombes BK Wickham ME Brown NF Lemire S Bossi L Hsiao WW Brinkman FS Finlay BB 《Journal of molecular biology》2005,348(4):817-830
165.
The cytokinetic Z ring is required for bacterial cell division. It consists of polymers of FtsZ, the bacterial ancestor of eukaryotic tubulin, linked to the cytoplasmic membrane. Formation of a Z ring in Escherichia coli occurs as long as one of two proteins, ZipA or FtsA, is present. Both of these proteins bind FtsZ suggesting that they might function to tether FtsZ filaments to the membrane. Although ZipA has a transmembrane domain and therefore can function as a membrane anchor, interaction of FtsA with the membrane has not been explored. In this study we demonstrate that FtsA, which is structurally related to eukaryotic actin, has a conserved C-terminal amphipathic helix that is essential for FtsA function. It is required to target FtsA to the membrane and subsequently to the Z ring. As FtsA is much more widely conserved in bacteria than ZipA, it is likely that FtsA serves as the principal membrane anchor for the Z ring. 相似文献
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A BAC library of 30,228 clones with an average insert size of 102 kb was constructed in the grass Brachypodium sylvaticum.
Brachypodium has a simple genome, similar in size and repetitive DNA content to that of rice, and is more closely related than rice both to the major temperate cereals wheat and barley, and to the forage grasses. The library represents 6.6 genome equivalents, implying a 99.9% probability of recovering any specific sequence. The library was arrayed onto two high-density colony filters, which were screened with heterologous DNA probes from rice chromosome nine and from syntenous regions of wheat, barley, maize and oat. The construction of Brachypodium BAC contigs revealed that synteny between rice, wheat and Brachypodium was largely maintained over several regions of rice chromosome nine. This suggests that Brachypodium will be a useful tool in the elucidation of gene content in agronomically important cereal crops, complementing rice as a grass genome model. 相似文献
168.
Honoré G. Ouattara Ban L. Koffi Germain T. Karou Abdourahamane Sangaré Sebastien L. Niamke Jacques K. Diopoh 《World journal of microbiology & biotechnology》2008,24(9):1753-1760
The role of bacilli in cocoa fermentation is not well known. Their potential of production of pectinolytic enzymes during
this process was evaluated. Bacillus growth was monitored and pectinolytic strains were screened for their use of pectin as sole carbon source. Effects of cocoa
fermentation parameters susceptible to influence on enzyme production were analysed. Among 98 strains isolated, 90 were positive
for pectin degradation and 80% of them presented detectable pectinolytic activities in submerged fermentation. Forty-eight
strains produced polygalacturonase (PG), 47 yielded pectin lyase (PL) and 23 strains produced both enzymes. Bacilli growth
was not significantly affected during fermentation. PL production was favoured by galactose, lactose, glucose as sugars, and
arginine, glutamine, cysteine and ammonium sulphate as nitrogen compounds. Pectin at low concentration (0.05%) and iron stimulated
PL production. It was strongly repressed by galacturonic acid (1%), and negatively affected by nitrogen starvation, zinc and
temperatures above 45°C. PL yield was very weak below pH 4.0 and in anaerobic conditions. PG production was weakened by sucrose
and cation depletion. It was increased slightly by cysteine, ammonium nitrate and nitrogen starvation and significantly above
40°C. PG synthesis was not affected by acidic pH (3.0–6.0) or oxygen availability. As fermentation products, lactate and acetate
lowered the production of both enzymes while ethanol had no effect. The high proportion of pectinolytic producers among the
strains studied and analysis of factors influencing pectinolytic enzymes production, suggest that Bacillus sp. is liable to produce at least one enzyme during cocoa fermentation. 相似文献
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Michael H Perlin Joelle Amselem Eric Fontanillas Su San Toh Zehua Chen Jonathan Goldberg Sebastien Duplessis Bernard Henrissat Sarah Young Qiandong Zeng Gabriela Aguileta Elsa Petit Helene Badouin Jared Andrews Dominique Razeeq Toni Gabaldón Hadi Quesneville Tatiana Giraud Michael E. Hood David J. Schultz Christina A. Cuomo 《BMC genomics》2015,16(1)