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Kopittke PM Menzies NW de Jonge MD McKenna BA Donner E Webb RI Paterson DJ Howard DL Ryan CG Glover CJ Scheckel KG Lombi E 《Plant physiology》2011,156(2):663-673
The phytotoxicity of trace metals is of global concern due to contamination of the landscape by human activities. Using synchrotron-based x-ray fluorescence microscopy and x-ray absorption spectroscopy, the distribution and speciation of copper (Cu), nickel (Ni), and zinc (Zn) was examined in situ using hydrated roots of cowpea (Vigna unguiculata) exposed to 1.5 μm Cu, 5 μm Ni, or 40 μm Zn for 1 to 24 h. After 24 h of exposure, most Cu was bound to polygalacturonic acid of the rhizodermis and outer cortex, suggesting that binding of Cu to walls of cells in the rhizodermis possibly contributes to the toxic effects of Cu. When exposed to Zn, cortical concentrations remained comparatively low with much of the Zn accumulating in the meristematic region and moving into the stele; approximately 60% to 85% of the total Zn stored as Zn phytate within 3 h of exposure. While Ni concentrations were high in both the cortex and meristem, concentrations in the stele were comparatively low. To our knowledge, this is the first report of the in situ distribution and speciation of Cu, Ni, and Zn in hydrated (and fresh) plant tissues, providing valuable information on the potential mechanisms by which they are toxic. 相似文献
104.
The HCO3− anion activates sperm motility, an important early step in capacitation, by increasing flagellar beat frequency through a pathway that requires the atypical adenylyl cyclase SACY and the sperm-specific Cα2 catalytic subunit of PKA. Here we show that the accelerating action of HCO3− also requires the continued presence of external Ca2+ (EC50 ∼ 0.5 mM), and find that Ca2+ can be replaced by Sr2+ but not by Mn2+. Ca2+ is required for HCO3− to elevate cAMP, but not for cAMP-AM to increase beat frequency, indicating that external Ca2+ acts before rather than after stimulation of SACY by HCO3−. With external Ca2+ present, HCO3− does not alter cytosolic or near-membrane [Ca2+]. Removal of external Ca2+ initiates a slow decline in intracellular [Ca2+] and rapid block of the HCO3−-evoked acceleration that is not relieved upon increasing internal [Ca2+] by rapid photolysis of caged Ca2+. We also find that the rapid (t1/2 ∼ 10 s) accelerating action of HCO3− is slowed more than three-fold by the carbonic anhydrase inhibitor acetazolamide. It is unaltered by the broad spectrum anion transport inhibitor SITS, and is not accompanied by detectable changes in intracellular pH. We propose that external Ca2+ binds an unidentified extracellular protein that is required for HCO3− to engage cAMP-mediated activation of motility. 相似文献
105.
Osama Odat Jason Gardiner Megan G. Sawchuk Carla Verna Tyler J. Donner Enrico Scarpella 《Genesis (New York, N.Y. : 2000)》2014,52(2):127-133
Patterning of numerous features of plants depends on transduction of the auxin signal. Auxin signaling is mediated by several pathways, the best understood of which relies on the function of the MONOPTEROS (MP) gene. Seven mp mutant alleles have been described in the widely used Columbia background of Arabidopsis: two extensively characterized and five only partially characterized. One of these five mp alleles appears to be extinct and thus unavailable for analysis. We show that two of the four remaining, partially characterized mp alleles reported to be in the Columbia background are in fact not in this background. We extend characterization of the remaining two Columbia alleles of mp, and we identify and characterize four new alleles of mp in the Columbia background, among which the first low‐expression allele of mp and the strongest Columbia allele of mp. These genetic resources provide the research community with new experimental opportunities for insight into the function of MP‐dependent auxin signaling in plant development. genesis 52:127–133. © 2013 Wiley Periodicals, Inc. 相似文献
106.
TR McClanahan SD Donner JA Maynard MA Macneil NA Graham J Maina AC Baker JB Alemu I M Beger SJ Campbell ES Darling CM Eakin SF Heron SD Jupiter CJ Lundquist E McLeod PJ Mumby MJ Paddack ER Selig R van Woesik 《PloS one》2012,7(8):e42884
Managing coral reefs for resilience to climate change is a popular concept but has been difficult to implement because the empirical scientific evidence has either not been evaluated or is sometimes unsupportive of theory, which leads to uncertainty when considering methods and identifying priority reefs. We asked experts and reviewed the scientific literature for guidance on the multiple physical and biological factors that affect the ability of coral reefs to resist and recover from climate disturbance. Eleven key factors to inform decisions based on scaling scientific evidence and the achievability of quantifying the factors were identified. Factors important to resistance and recovery, which are important components of resilience, were not strongly related, and should be assessed independently. The abundance of resistant (heat-tolerant) coral species and past temperature variability were perceived to provide the greatest resistance to climate change, while coral recruitment rates, and macroalgae abundance were most influential in the recovery process. Based on the 11 key factors, we tested an evidence-based framework for climate change resilience in an Indonesian marine protected area. The results suggest our evidence-weighted framework improved upon existing un-weighted methods in terms of characterizing resilience and distinguishing priority sites. The evaluation supports the concept that, despite high ecological complexity, relatively few strong variables can be important in influencing ecosystem dynamics. This is the first rigorous assessment of factors promoting coral reef resilience based on their perceived importance, empirical evidence, and feasibility of measurement. There were few differences between scientists' perceptions of factor importance and the scientific evidence found in journal publications but more before and after impact studies will be required to fully test the validity of all the factors. The methods here will increase the feasibility and defensibility of including key resilience metrics in evaluations of coral reefs, as well as reduce costs. Adaptation, marine protected areas, priority setting, resistance, recovery. 相似文献
107.
We have developed a simple method for measuring the missense substitution of amino acids at specified positions in proteins synthesized in vivo. We find that the frequency of cysteine substitution for the single arginine in Escherichia coli ribosomal protein L7/L12 is close to 10(-3) for wild-type bacteria, decreases to 4 x 10(-4) in streptomycin-resistant bacteria containing mutant S12 (rpsL), and is virtually unchanged in Ram bacteria containing mutant S4 (rpsD). We have also found that the frequency of the cysteine substitution for the single tryptophan in E. coli ribosomal protein S6 is 3-4 x 10(-3) for wild-type bacteria, decreases to 6 x 10(-4) in streptomycin-resistant bacteria and is elevated to nearly 10(-2) in Ram bacteria. 相似文献
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109.
Shen W Fakhoury S Donner G Henry K Lee J Zhang H Cohen J Warner R Saeed B Cherian S Tahir S Kovar P Bauch J Ng SC Marsh K Sham H Rosenberg S 《Bioorganic & medicinal chemistry letters》1999,9(5):703-708
Synthesis and biological evaluation of heteroarenes as reduced cysteine replacements are described. Of the heteroaryl groups examined with respect to FT inhibitor FTI-276 (1), pyridyl was the replacement found to be most effective. Substitutions at C4 of the pyridyl moiety did not affect the in vitro activity. Compound 9a was found to have moderate in vivo bioavailability. 相似文献
110.
Donner PL Xie Q Pratt JK Maring CJ Kati W Jiang W Liu Y Koev G Masse S Montgomery D Molla A Kempf DJ 《Bioorganic & medicinal chemistry letters》2008,18(8):2735-2738
In our program to discover non-nucleoside, small molecule inhibitors of genotype 1 HCV polymerase, we investigated a series of promising analogs based on a benzothiadiazine screening hit that contains an ABCD ring system. After demonstrating that a methylsulfonylamino D-ring substituent increased the enzyme potency into the low nanomolar range, we explored a minimum core required for activity by truncating to a three-ring system. Described herein are the syntheses and structure-activity relationship of a set of inhibitors lacking the A-ring of an ABCD ring system. We observed that small aromatic rings and alkenyl groups appended to the 5-position of the B-ring were optimal, resulting in inhibitors with low nanomolar potencies. 相似文献