Differential divergences of obligately insect-pathogenic Entomophthora species from fly and aphid hosts

Three DNA regions (ITS 1, LSU rRNA and GPD) of isolates from the insect-pathogenic fungus genus Entomophthora originating from different fly (Diptera) and aphid (Hemiptera) host taxa were sequenced. The results documented a large genetic diversity among the fly-pathogenic Entomophthora and only minor differences among aphid-pathogenic Entomophthora. The evolutionary time of divergence of the fly and the aphid host taxa included cannot account for this difference. The host-driven divergence of Entomophthora, therefore, has been much greater in flies than in aphids. Host-range differences or a recent host shift to aphid are possible explanations.Centro de Estudios Parasitológicos y de Vectore

Differential divergences of obligately insect-pathogenic Entomophthora species from fly and aphid hosts

Three DNA regions (ITS 1, LSU rRNA and GPD) of isolates from the insect-pathogenic fungus genus Entomophthora originating from different fly (Diptera) and aphid (Hemiptera) host taxa were sequenced. The results documented a large genetic diversity among the fly-pathogenic Entomophthora and only minor differences among aphid-pathogenic Entomophthora. The evolutionary time of divergence of the fly and the aphid host taxa included cannot account for this difference. The host-driven divergence of Entomophthora, therefore, has been much greater in flies than in aphids. Host-range differences or a recent host shift to aphid are possible explanations.Centro de Estudios Parasitológicos y de Vectore

A systematic survey of an intragenic epistatic landscape [preprint]

Mutations are the source of evolutionary variation. The interactions of multiple mutations can have important effects on fitness and evolutionary trajectories. We have recently described the distribution of fitness effects of all single mutations for a nine amino acid region of yeast Hsp90 (Hsp82) implicated in substrate binding. Here, we report and discuss the distribution of intragenic epistatic effects within this region in seven Hsp90 point mutant backgrounds of neutral to slightly deleterious effect, resulting in an analysis of more than 1000 double-mutants. We find negative epistasis between substitutions to be common, and positive epistasis to be rare – resulting in a pattern that indicates a drastic change in the distribution of fitness effects one step away from the wild type. This can be well explained by a concave relationship between phenotype and genotype (i.e., a concave shape of the local fitness landscape), suggesting mutational robustness intrinsic to the local sequence space. Structural analyses indicate that, in this region, epistatic effects are most pronounced when a solvent-inaccessible position is involved in the interaction. In contrast, all 18 observations of positive epistasis involved at least one mutation at a solvent-exposed position. By combining the analysis of evolutionary and biophysical properties of an epistatic landscape, these results contribute to a more detailed understanding of the complexity of protein evolution

Theorizing the Transcendent Persona: Amelia Earhart’s Vision in The Fun of It

In this article, we define and theorize the ‘‘transcendent persona,’’ a discursive strategy in which a rhetor draws from a boundary-breaking accomplishment and utilizes the symbolic capital of that feat to persuasively delineate unconventional ways of communicating and behaving in society. Aviator Amelia Earhart’s autobiography The Fun of It (1932) functions as an instructive representative anecdote of this concept and demonstrates that the transcendent persona’s persuasive force hinges on one’s ability to balance distance from audiences with similarities to them. Striking such a balance creates a platform for rhetors to promote transformative visions of society. Earhart utilized the transcendent persona to illustrate an alternative vocabulary of what contemporary theorists might call feminine gender performativity. The article concludes by exploring the implications of the transcendent persona as an enduring, rhetorical resource for communicators, as well as for scholars of persuasion and social change, religious communication, and communication history

Theorizing the Transcendent Persona: Amelia Earhart’s Vision in The Fun of It

In this article, we define and theorize the ‘‘transcendent persona,’’ a discursive strategy in which a rhetor draws from a boundary-breaking accomplishment and utilizes the symbolic capital of that feat to persuasively delineate unconventional ways of communicating and behaving in society. Aviator Amelia Earhart’s autobiography The Fun of It (1932) functions as an instructive representative anecdote of this concept and demonstrates that the transcendent persona’s persuasive force hinges on one’s ability to balance distance from audiences with similarities to them. Striking such a balance creates a platform for rhetors to promote transformative visions of society. Earhart utilized the transcendent persona to illustrate an alternative vocabulary of what contemporary theorists might call feminine gender performativity. The article concludes by exploring the implications of the transcendent persona as an enduring, rhetorical resource for communicators, as well as for scholars of persuasion and social change, religious communication, and communication history

Dynamic assembly and sustained retention of 53BP1 at the sites of DNA damage are controlled by Mdc1/NFBD1

53BP1 is a key component of the genome surveillance network activated by DNA double strand breaks (DSBs). Despite its known accumulation at the DSB sites, the spatiotemporal aspects of 53BP1 interaction with DSBs and the role of other DSB regulators in this process remain unclear. Here, we used real-time microscopy to study the DSB-induced redistribution of 53BP1 in living cells. We show that within minutes after DNA damage, 53BP1 becomes progressively, yet transiently, immobilized around the DSB-flanking chromatin. Quantitative imaging of single cells revealed that the assembly of 53BP1 at DSBs significantly lagged behind Mdc1/NFBD1, another DSB-interacting checkpoint mediator. Furthermore, short interfering RNA-mediated ablation of Mdc1/NFBD1 drastically impaired 53BP1 redistribution to DSBs and triggered premature dissociation of 53BP1 from these regions. Collectively, these in vivo measurements identify Mdc1/NFBD1 as a key upstream determinant of 53BP1's interaction with DSBs from its dynamic assembly at the DSB sites through sustained retention within the DSB-flanking chromatin up to the recovery from the checkpoint

Delayed Hypersensitivity to Nanosecond Pulsed Electric Field in Electroporated Cells

We demonstrate that conditioning of mammalian cells by electroporation with nanosecond pulsed electric field (nsPEF) facilitates their response to the next nsPEF treatment. The experiments were designed to unambiguously separate the electroporation-induced sensitization and desensitization effects. Electroporation was achieved by bursts of 300-ns, 9 kV/cm pulses (50 Hz, n = 3–100) and quantified by propidium dye uptake within 11 min after the nsPEF exposure. We observed either sensitization to nsPEF or no change (when the conditioning was either too weak or too intense, or when the wait time after conditioning was too short). Within studied limits, conditioning never caused desensitization. With settings optimal for sensitization, the second nsPEF treatment became 2.5 times (25 °C) or even 6 times (37 °C) more effective than the same nsPEF treatment delivered without conditioning. The minimum wait time required for sensitization development was 30 s, with still longer delays increasing the effect. We show that the delayed hypersensitivity was not mediated by either cell swelling or oxidative effect of the conditioning treatment; biological mechanisms underlying the delayed electrosensitization remain to be elucidated. Optimizing nsPEF delivery protocols to induce sensitization can reduce the dose and adverse side effects of diverse medical treatments which require multiple pulse applications

The Cytotoxic Synergy of Nanosecond Electric Pulses and Low Temperature Leads to Apoptosis

Electroporation by nanosecond electric pulses (nsEP) is an emerging modality for tumor ablation. Here we show the efficient induction of apoptosis even by a non-toxic nsEP exposure when it is followed by a 30-min chilling on ice. This chilling itself had no impact on the survival of U-937 or HPAF-II cells, but caused more than 75% lethality in nsEP-treated cells (300 ns, 1.8-7 kV/cm, 50-700 pulses). The cell death was largely delayed by 5-23 hr and was accompanied by a 5-fold activation of caspase 3/7 (compared to nsEP without chilling) and more than 60% cleavage of poly-ADP ribose polymerase (compared to less than 5% in controls or after nsEP or chilling applied separately). When nsEP caused a transient permeabilization of 83% of cells to propidium iodide, cells placed at 37 ° C resealed in 10 min, whereas 60% of cells placed on ice remained propidium-permeable even in 30 min. The delayed membrane resealing caused cell swelling, which could be blocked by an isosmotic addition of a pore-impermeable solute (sucrose). However, the block of swelling did not prevent the delayed cell death by apoptosis. The potent enhancement of nsEP cytotoxicity by subsequent non-damaging chilling may find applications in tumor ablation therapies