The Effect of Temperature on Flowers

Andrews, F. M.

doi:10.1104/pp.4.2.281

Cited by 35 publications

(40 citation statements)

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“…The maximum iron capacity measured under the conditions tested was ∼2700. This is significantly less than theoretical value of ∼4500 (30, 31) calculated for mammalian ferritin under the assumption that the crystalline core has a ferrihydrite-like structure (i.e., 5Fe 2 O 3 ‚9H 2 O) (32-34) but significantly greater than the average iron content of BFR cores isolated from nonoverxpressing strains (2). An effective capacity well under 4500 was also recently observed for horse spleen ferritin (35).…”

Section: Discussionmentioning

confidence: 67%

“…To investigate how the amount 2 Iron per protein is in the form of iron(III) bound per protein rather than iron(II) added per protein, because not all of the added iron is assimilated into the protein core. 3 A340nm traces resulting from the autoxidation of iron(II) are complex, presumably due to a dependence of the rate on the presence of precipitated iron(III) mineral.…”

Section: Resultsmentioning

confidence: 99%

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Core Formation in Escherichia coli Bacterioferritin Requires a Functional Ferroxidase Center

et al. 2003

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Bacterioferritin from Escherichia coli is able to accumulate large quantities of iron in the form of an inorganic iron(III) mineral core. Core formation in the wild-type protein and a number of ferroxidase center variants was studied to determine key features of the core formation process and, in particular, the role played by the ferroxidase center. Core formation rates were found to be iron(II)-dependent and also depended on the amount of iron already present in the core, indicating the importance of the core surface in the mineralization reaction. Core formation was also found to be pH-dependent in terms of both rate and iron-loading characteristics, occurring with maximum efficiency at pH 6.5. Even at this optimum pH, however, the effective iron capacity was approximately 2700 per molecule, i.e., well below the theoretical limit of approximately 4500, suggesting that competing oxidation/precipitation processes have a major influence on the amount of iron accumulated. Disruption of the ferroxidase center, by site-directed mutagenesis or by chemical inhibition with zinc(II), had a profound effect on core formation. Effective iron capacities were found to be linked to iron(II) oxidation rates, and in zinc(II)-inhibited wild-type and E18A bacterioferritins core formation was severely restricted. Zinc(II) was also able, even at low stoichiometries (12-60 ions/protein), to significantly inhibit further core formation in protein already containing a substantial core, indicating the importance of the ferroxidase center throughout the core formation process. A mechanism is proposed that incorporates essential roles for the core surface and the ferroxidase center. A central feature of this mechanism is that dioxygen cannot readily gain access to the core, perhaps because the channels through the bacterioferritin coat are hydrophilic and dioxygen is nonpolar.

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Section: Discussionmentioning

confidence: 67%

Section: Resultsmentioning

confidence: 99%

Core Formation in Escherichia coli Bacterioferritin Requires a Functional Ferroxidase Center

et al. 2003

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“…tularensis . Increasing global temperatures may allow for higher quantities of both mosquitoes and nectar-bearing flowers to exist seasonally due to more favorable growth conditions [34, 35]. Therefore, mosquito-borne tularemia, which is largely dependent upon weather patterns, may present an increased abundance in years to come.…”

Section: Discussionmentioning

confidence: 99%

The potential for flower nectar to allow mosquito to mosquito transmission of Francisella tularensis

et al. 2017

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Francisella tularensis is disseminated in nature by biting arthropods such as mosquitoes. The relationship between mosquitoes and F. tularensis in nature is highly ambiguous, due in part to the fact that mosquitoes have caused significant tularemia outbreaks despite being classified as a mechanical vector of F. tularensis. One possible explanation for mosquitoes being a prominent, yet mechanical vector is that these insects feed on flower nectar between blood meals, allowing for transmission of F. tularensis between mosquitoes. Here, we aimed to assess whether F. tularensis could survive in flower nectar. Moreover, we examined if mosquitoes could interact with or ingest and transmit F. tularensis from one source of nectar to another. F. tularensis exhibited robust survivability in flower nectar with concentrations of viable bacteria remaining consistent with the rich growth medium. Furthermore, F. tularensis was able to survive (albeit to a lesser extent) in 30% sucrose (a nectar surrogate) over a period of time consistent with that of a typical flower bloom. Although we observed diminished bacterial survival in the nectar surrogate, mosquitoes that fed on this material became colonized with F. tularensis. Finally, colonized mosquitoes were capable of transferring F. tularensis to a sterile nectar surrogate. These data suggest that flower nectar may be capable of serving as a temporary source of F. tularensis that could contribute to the amplification of outbreaks. Mosquitoes that feed on an infected mammalian host and subsequently feed on flower nectar could deposit some F. tularensis bacteria into the nectar in the process. Mosquitoes subsequently feeding on this nectar source could potentially become colonized by F. tularensis. Thus, the possibility exists that flower nectar may allow for vector-vector transmission of F. tularensis.

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“…On the other hand, the Fe storage function of E. coli bacterial ferritin (EcFtnA) has been demonstrated both in vitro 31 and in vivo . 32 Amino-acid sequence comparisons and X-ray crystallographic studies 9,33 showed that EcFtnA contains a substrate Fe binding site that is homologous to the diiron binding ferroxidase center of H-type ferritins (sites A and B ). And, intriguingly, the X-ray crystallographic studies of EcFtnA 7,9,33 further revealed the presence of a third Fe binding site (site C ) in the vicinity of the H-type diiron ferroxidase center.…”

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confidence: 99%

Spectroscopic Evidence for and Characterization of a Trinuclear Ferroxidase Center in Bacterial Ferritin from Desulfovibrio vulgaris Hildenborough

et al. 2012

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Ferritins are ubiquitous and can be found in practically all organisms that utilize Fe. They are composed of 24 subunits forming a hollow sphere with an inner cavity of ~80 Å in diameter. The main function of ferritin is to oxidize the cytotoxic Fe2+ ions and store the oxidized Fe in the inner cavity. It has been established that the initial step of rapid oxidation of Fe2+ (ferroxidation) by H-type ferritins, found in vertebrates, occurs at a diiron binding center, termed ferroxidase center. In bacterial ferritins, however, X-ray crystallographic evidence and amino-acid sequence analysis revealed a trinuclear Fe binding center comprising a binuclear Fe binding center (sites A and B), homologous to the ferroxidase center of H-type ferritin, and an adjacent mononuclear Fe binding site (site C). In an effort to obtain further evidence supporting the presence of a trinuclear Fe binding center in bacterial ferritins and to gain information on the states of the iron bound to the trinuclear center, bacterial ferritin from Desulfovibrio vulgaris (DvFtn) and its E130A variant were loaded with sub-stoichiometric amounts of Fe2+ and products were characterized by Mössbauer and EPR spectroscopy. Four distinct Fe species were identified: a paramagnetic diferrous species, a diamagnetic diferrous species, a mixed valence Fe2+Fe3+ species and a mononuclear Fe2+ species. The latter three species were detected in the wild-type DvFtn, while the paramagnetic diferrous species was detected in the E130A variant. These observations can be rationally explained by the presence of a trinuclear Fe binding center, and the four Fe species can be properly assigned to the three Fe binding sites. Further, our spectroscopic data suggest that (1) the fully occupied trinuclear center supports an all ferrous state, (2) site B and C are bridged by a μ-OH group forming a diiron sub-center within the trinuclear center, and (3) this sub-center can afford both a mixed valence Fe2+Fe3+ state and a diferrous state. Mechanistic insights provided by these new findings are discussed and a minimal mechanistic scheme involving O-O bond cleavage is proposed.

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The Effect of Temperature on Flowers

Abstract: This paper is concerned with the opening and closing processes in the flowers of Crocus and Tulipa. As is well known from the work of PFEFFER, the flowers of Crocus and Tulipa are only slightly photonastic. They are, however, extremely thermonastic.

Cited by 35 publications

References 0 publications

Core Formation in Escherichia coli Bacterioferritin Requires a Functional Ferroxidase Center

Core Formation in Escherichia coli Bacterioferritin Requires a Functional Ferroxidase Center

The potential for flower nectar to allow mosquito to mosquito transmission of Francisella tularensis

Spectroscopic Evidence for and Characterization of a Trinuclear Ferroxidase Center in Bacterial Ferritin from Desulfovibrio vulgaris Hildenborough

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