Coordination Chemistry and Redox Processes in Siderophore-Mediated Iron Transport

In this mini-review we present an environmental iron mobility/transport scheme consisting of inter-related controls, whereby the first coordination shell of iron modulates the iron redox potential (E_1/2), and the oxidation state of iron controls the chemistry of the first coordination sphere and therefore the immediate chemical environment of the iron. Siderophores (microbially generated iron specific chelators) may be viewed as iron redox mediators. Siderophore chelation of environmental iron in a reduced (Fe(II)) oxidation state results in facile air oxidation of iron due to the negative redox potentials observed for Fe-siderophore complexes. This solubilizes the iron and locks it into a specific coordination environment, thereby preventing hydrolysis and precipitation. The high-spin Fe³⁺ → Fe⁺ electron transfer process may be viewed as a switch that controls the thermodynamic stability and kinetic lability of the first coordination shell. Reduction of iron(III)-siderophore complexes to iron(II)-siderophore complexes decreases thermodynamic stability, increases the rate of siderophore ligand exchange, and increases the ease of siderophore donor atom protonation, thus facilitating a rapid turnover of the first coordination shell. Results are presented for iron-siderophore pH and oxidation state dependent speciation studies that are relevant to environmental and microbial iron mobility and transport.     

Saccharum × Miscanthus intergeneric hybrids (miscanes) exhibit greater chilling tolerance of C4 photosynthesis and postchilling recovery than sugarcane (Saccharum spp. hybrids)

Although commercial sugarcane (Saccharum spp. hybrid) produces large biomass yields, its lack of cold tolerance limits its cultivation to the tropics and subtropics. In contrast, sugarcane's close relative, Miscanthus, tolerates low temperatures. We studied 18 miscane genotypes, derived from hybridizations between two genotypes of sugarcane and two genotypes of Miscanthus (one each of M. sinensis and M. sacchariflorus). In an initial greenhouse experiment on long‐duration chilling stress (12–13°C day/7–9°C night), photosynthetic rates of the Miscanthus parents were significantly higher than the sugarcane parents after 7 days of chilling and were more than double by 14 days. The Miscanthus also retained more of their prechilling (22–25°C day/13–15°C night) photosynthetic rates (68%–72% 7 days, 64%–66% 14 days) than the sugarcanes (27% 7 days, 19%–20% 14 days). Seven of 18 miscanes exhibited higher photosynthetic rates than their sugarcane parents after 7 days of chilling, whereas after 14 days only four miscane genotypes had significantly higher photosynthetic rates than their sugarcane parents, but notably two of these did not differ from their highly tolerant Miscanthus parents. In a subsequent growth chamber experiment to evaluate short‐duration chilling stress and postchilling recovery, three miscanes representing the range of responses observed in the greenhouse experiment were compared with their parents. After 4 days of chilling (12/7°C day/night), the miscanes retained between 45% and 60% of their prechilling photosynthetic rate, with the best entry not significantly different from its Miscanthus parent (66%), and all three miscanes performed significantly better than the sugarcane parents (32%–33% for sugarcanes). After 7 days of postchilling recovery (26/18°C day/night), the Miscanthus parents and two of the miscanes fully recovered their prechilling photosynthetic rates but the sugarcane parents only recovered 69%–73% of their prechilling rates. Thus, genes from Miscanthus can be used to improve chilling tolerance of sugarcane via introgression.     

Anticipation of Antigenic Sites for the Goal of Vaccine Designing Against Nipah Virus: An Immunoinformatics Inquisitive Quest

International Journal of Peptide Research and Therapeutics - With time, the Nipah virus has been proved as a fatal and dangerous pathogen for humanity. Nipah virus has its origin from bats and...     

Chromatin and epigenetics in all their states: Meeting report of the first conference on Epigenetic and Chromatin Regulation of Plant Traits - January 14 – 15, 2016 - Strasbourg,France

In January 2016, the first Epigenetic and Chromatin Regulation of Plant Traits conference was held in Strasbourg, France. An all-star lineup of speakers, a packed audience of 130 participants from over 20 countries, and a friendly scientific atmosphere contributed to make this conference a meeting to remember. In this article we summarize some of the new insights into chromatin, epigenetics, and epigenomics research and highlight nascent ideas and emerging concepts in this exciting area of research.     

Chemoprevention of BBN-Induced Bladder Carcinogenesis by the Selective Estrogen Receptor Modulator Tamoxifen

Bladder cancer is the fifth most frequent tumor in men and ninth in women in the United States. Due to a high likelihood of recurrence, effective chemoprevention is a significant unmet need. Estrogen receptors (ERs), primarily ERβ, are expressed in normal urothelium and urothelial carcinoma, and blocking ER function with selective ER modulators such as tamoxifen inhibits bladder cancer cell proliferation in vitro. Herein, the chemoprotective potential of tamoxifen was evaluated in female mice exposed to the bladder-specific carcinogen, N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN). Carcinogen treatment resulted in a 76% tumor incidence and increased mean bladder weights in comparison to controls. In contrast, mice receiving tamoxifen concurrent (8–20 weeks) or concurrent and subsequent (8–32 weeks) to BBN administration had no change in bladder weight and only 10% to 14% incidence of tumors. Non-muscle-invasive disease was present in animals treated with tamoxifen before (5–8 weeks) or after (20–32 weeks) BBN exposure, while incidence of muscle-invasive bladder carcinoma was reduced. ERβ was present in all mice and thus is a potential mediator of the tamoxifen chemoprotective effect. Surprisingly, ERα expression, which was detected in 74% of the mice exposed to BBN alone but not in any controlmice, was correlated with tumor incidence, indicating a possible role for this receptor in carcinogen-induced urothelial tumorigenesis. Thus, these data argue that both ERα and ERβ play a role in modulating carcinogen-induced bladder tumorigenesis. Administration of tamoxifen should be tested as a chemopreventive strategy for patients at high risk for bladder cancer recurrence.