Role of aminocyclopropane-l-carboxylic acid in ethylene release by distal tissues following localized application of ethephon in Cucurbita pepo

The application of ethephon to a single leaf of Cucurbita pepo L. cv. Trailing Marrow plants caused a huge increase in ethylene production from the treated organ and an increased rate of ethylene production from other parts of the plant. These increases were particularly marked in the shoot apex and expanding leaf. Prior treatment with aminoethoxyvinylglycine (AVG), an ethylene biosynthesis inhibitor, blocked the increased production of ethylene at sites distant from the point of ethephon application. This strongly suggests that the increased ethylene production at these distant sites is due to ethylene biosynthesis and not a result of the translocation of ethylene released by the breakdown of ethephon at the site of application. Assays of 1-aminocyclopropane-l-carboxylic acid (ACC), an ethylene precursor, showed that it increased substantially after ethephon application but was at undetectable levels in the presence of AVG. It is proposed that the application of ethephon stimulates ethylene biosynthesis, but that transport through the plants is effected by ACC which is then converted to ethylene at the shoot apex and leaves.     

Structural and Biochemical Characterization of Chlamydia trachomatis Hypothetical Protein CT263 Supports That Menaquinone Synthesis Occurs through the Futalosine Pathway

The obligate intracellular human pathogen Chlamydia trachomatis is the etiological agent of blinding trachoma and sexually transmitted disease. Genomic sequencing of Chlamydia indicated this medically important bacterium was not exclusively dependent on the host cell for energy. In order for the electron transport chain to function, electron shuttling between membrane-embedded complexes requires lipid-soluble quinones (e.g. menaquionone or ubiquinone). The sources or biosynthetic pathways required to obtain these electron carriers within C. trachomatis are poorly understood. The 1.58Å crystal structure of C. trachomatis hypothetical protein CT263 presented here supports a role in quinone biosynthesis. Although CT263 lacks sequence-based functional annotation, the crystal structure of CT263 displays striking structural similarity to 5′-methylthioadenosine nucleosidase (MTAN) enzymes. Although CT263 lacks the active site-associated dimer interface found in prototypical MTANs, co-crystal structures with product (adenine) or substrate (5′-methylthioadenosine) indicate that the canonical active site residues are conserved. Enzymatic characterization of CT263 indicates that the futalosine pathway intermediate 6-amino-6-deoxyfutalosine (k_cat/K_m = 1.8 × 10³ m⁻¹ s⁻¹), but not the prototypical MTAN substrates (e.g. S-adenosylhomocysteine and 5′-methylthioadenosine), is hydrolyzed. Bioinformatic analyses of the chlamydial proteome also support the futalosine pathway toward the synthesis of menaquinone in Chlamydiaceae. This report provides the first experimental support for quinone synthesis in Chlamydia. Menaquinone synthesis provides another target for agents to combat C. trachomatis infection.     

"The City Is My Mother": Narratives of Schizophrenia and Homelessness

Recent narrative analysis in medical anthropology provides keys to both the personal meaning of illness and the historical, cultural, and institutional shaping of that experience. Yet Western psychiatric thinking and practice continue to view schizophrenic discourse as closed to interpretation. Caught in this "closed text," the self would seem obliterated. But using narratives of schizophrenia and homelessness, this essay proposes a different understanding of schizophrenic alterity. The openness of the text-as-experience is re-created collectively, from outside the subject's narration: the subject's "self is construction through the added perspectives of his or her interlocutors in the role of storymakers.     

Regional Central Nervous System Oligosaccharide Storage in Caprine β-Mannosidosis

Goats affected with beta-mannosidosis, an autosomal recessive disease of glycoprotein metabolism, have deficient activity of the lysosomal enzyme beta-mannosidase along with tissue storage of oligosaccharides, including a trisaccharide [Man(beta 1-4)GlcNAc(beta 1-4)GlcNAc] and a disaccharide [Man(beta 1-4)GlcNAc]. CNS myelin deficiency, with regional variation in severity, is a major pathological characteristic of affected goats. This study was designed to investigate regional CNS differences in oligosaccharide accumulation to assess the extent of correlation between oligosaccharide accumulation and severity of myelin deficits. The concentrations of accumulated disaccharide and trisaccharide and the activity of beta-mannosidase were determined in cerebral hemisphere gray and white matter and in spinal cord from three affected and two control neonatal goats. In affected goats, the content of trisaccharide and disaccharide in spinal cord (moderate myelin deficiency) was similar to or greater than that in cerebral hemispheres (severe myelin deficiency). Thus, greater oligosaccharide accumulation was not associated with more severe myelin deficiency. Regional beta-mannosidase activity levels in control goats were consistent with the affected goat oligosaccharide accumulation pattern. The similarity of trisaccharide and disaccharide content in cerebral hemisphere gray and white matter suggested that lysosomal storage vacuoles, more numerous in gray matter, may not be the only location of stored CNS oligosaccharides.     

Posters for accident departments: simple method of sustaining reduction in x ray examinations.

OBJECTIVE--To assess whether a simple strategy would sustain a reduction in the number of unnecessary x ray examinations. DESIGN--Use of posters to display guidelines encouraging the more effective use of radiology in patients with head injuries, twisted ankles, neck injuries, and abdominal pain. SETTING--Accident department of a large metropolitan district general hospital. PATIENTS--15,875 patients attending the accident department over two years. MAIN OUTCOME MEASURE--Proportion of patients having radiography. RESULTS--Referrals for skull radiography fell from 56% to 20% and those for abdominal radiography fell from 31% to 7%. Referral patterns for adults attending with twisted ankles and cervical spine injuries did not change. Reductions were sustained over two years. CONCLUSION--Carefully designed posters provide a simple method of reducing unnecessary x ray examinations.     

Isolation, Mapping, and Functional Expression of the Mouse X Chromosome Glycerol Kinase Gene

Glycerol kinase (Gyk) participates in the metabolism of endogenously derived and dietary glycerol. Deficiency of the human enzyme activity is an X-linked recessive disorder with a clinical picture varying from childhood metabolic crisis to asymptomatic adults incidentally identified by hyperlipidemia screening (pseudohypertriglyceridemia). Gyk is a member of a small group of kinases termed ambiquitous enzymes that are found in the cytosol or as membrane-bound enzymes associated with the voltage-dependent anion channel of the mitochondrial outer membrane. It was recently reported that in humans there are X-linked and autosomal copies of Gyk sequences, both apparently functional genes and processed pseudogenes. To understand the role of Gyk in normal metabolism and the variable clinical features seen with Gyk deficiency, we have characterized the mouse Gyk gene. We present the sequence of a full-length mouse Gyk cDNA that is alternatively spliced in brain. The Gyk gene was mapped to the mouse X chromosome by both fluorescencein situhybridization and an interspecies backcross panel, demonstrating conservation of synteny withdmd.To confirm the functional identity of the cDNA, transient transfection of the cDNA into COS7 cells was shown to cause a marked elevation in glycerol kinase activity.     

Promises and Challenges of Eco-Physiological Genomics in the Field: Tests of Drought Responses in Switchgrass

Identifying the physiological and genetic basis of stress tolerance in plants has proven to be critical to understanding adaptation in both agricultural and natural systems. However, many discoveries were initially made in the controlled conditions of greenhouses or laboratories, not in the field. To test the comparability of drought responses across field and greenhouse environments, we undertook three independent experiments using the switchgrass reference genotype Alamo AP13. We analyzed physiological and gene expression variation across four locations, two sampling times, and three years. Relatively similar physiological responses and expression coefficients of variation across experiments masked highly dissimilar gene expression responses to drought. Critically, a drought experiment utilizing small pots in the greenhouse elicited nearly identical physiological changes as an experiment conducted in the field, but an order of magnitude more differentially expressed genes. However, we were able to define a suite of several hundred genes that were differentially expressed across all experiments. This list was strongly enriched in photosynthesis, water status, and reactive oxygen species responsive genes. The strong across-experiment correlations between physiological plasticity—but not differential gene expression—highlight the complex and diverse genetic mechanisms that can produce phenotypically similar responses to various soil water deficits.Crop productivity and wild plant distributions are governed by the availability of soil moisture (Axelrod, 1972; Boyer, 1982; Ciais et al., 2005). The impact of drought and soil water deficit in agriculture is estimated to be the largest abiotic determinant of yield (Boyer, 1982; Araus et al., 2002), while drought is also considered a primary cause of speciation and adaptation in nature (Stebbins, 1952). Dehydration avoidance and other drought adaptive strategies permit plants to survive or maintain growth during periodic droughts (Blum, 1996; Chaves et al., 2003; Chaves and Oliveira, 2004). Specifically, phenotypic plasticity of stomatal conductance, water foraging, and growth traits (among many others) may effectively maintain homeostasis of leaf water potential despite soil water deficits.Leaf water potential is a bellwether of the physiological impact of water deficit (Jones, 2007). Under drought, decreasing water availability results in reduced leaf water potentials and a sequence of physiological responses including reduced photosynthesis, growth rate, and ultimately, fitness (Taiz and Zeiger, 2014). Plants therefore seek to maintain homeostasis of leaf water potential, with the highest (least negative) values supporting the most efficient functioning of photosynthesis and other metabolic processes in most species (Lawlor and Fock, 1978; Turner and Begg, 1981; Kramer and Boyer, 1995; Cornic and Massacci, 1996; Jones, 2007). Plants that exhibit dehydration avoidance strategies compensate for soil water deficit through phenotypic plasticity of gene expression (Verslues et al., 2006; DesMarais and Juenger, 2010; DesMarais et al., 2013; Lovell et al., 2015) and downstream physiological phenotypes (Levitt, 1980), among others.To understand plant stress responses, it is critical to determine the physiological and genetic underpinnings of drought adaptation in both field and laboratory conditions (Travers et al., 2007; Gaudin et al., 2013). A common finding among such studies is that physiological and gene expression responses to drought vary considerably depending on the severity and temporal dynamics of drying soil (Chaves et al., 2003; Barker et al., 2005; Malmberg et al., 2005; Mittler, 2006; Mishra et al., 2012). Natural soil moisture variation, which has shaped adaptive responses to drought in wild populations, is not necessarily recapitulated by controlled (often, “shock”) laboratory experiments. For example, single abiotic stresses rarely occur in isolation in the field (Mittler, 2006). Instead, wild and crop plants respond to the combination of diverse stressors such as drought, heat, and salinity, simultaneously and at both molecular (e.g. Rizhsky et al., 2002; Rizhsky et al., 2004; Suzuki et al., 2005) and physiological (e.g. Heyne and Brunson, 1940; Craufurd and Peacock, 1993; Machado and Paulsen, 2001) levels. Therefore, inquiries into evolved plant stress responses are perhaps best served by experimental conditions that emulate selective agents in the field. Given that the extent and severity of stress causes qualitatively different physiological responses, it is not surprising that several studies have found relatively weak genetic correlations between laboratory phenotypes and those collected in the field (e.g. Weinig et al., 2002; Malmberg et al., 2005; Anderson et al., 2011; Mishra et al., 2012).Soil properties and biota can also affect plant growth and physiology (Meisner et al., 2013; Schweitzer et al., 2014), which may be exacerbated by contrasts between growth in potting mix or in native soil (Rowe et al., 2007; Heinze et al., 2016). The observation that field-grown plants have different root systems and greater total water storage than those in greenhouse pots is of particular importance to water relations (Poorter et al., 2012a). Short-term drought stress in the field may be buffered by access to larger volumes of soil and more complex root-soil-water dynamics, conditions poorly represented in most controlled settings.The field of experimental design has been fundamentally shaped by a central problem of biology: that it is notoriously difficult to control environmental factors in the field (Jones, 2013). A classic solution is to increase biological replication, but this is generally not feasible with costly and time-sensitive physiological and genetic assays (Poorter et al., 2012b; Marchand et al., 2013). Despite these difficulties, understanding the effects of drought in field conditions is necessary because it is in these settings that yield is impacted and selection is acting to shape adaptive responses to stress. Here, we determine how the interplay between drought severity, planting condition (e.g. field, potted, greenhouse) and sampling timing impacts physiological and genomic responses to drought in the C₄ perennial grass, Panicum virgatum (switchgrass). To accomplish this, we used observations collected from clonally replicated individuals of the “AP13” switchgrass genotype (derived from the Alamo cultivar), which is the genome reference for this important biofuel crop and dominant member of mesic tall grass prairie ecosystems. The Alamo cultivar is a southern lowland accession that has high vigor and performance across a variety of climatic conditions. Replicates were grown in three separate soil moisture manipulation experiments with distinct rooting environments: in medium sized pots in a greenhouse, in large containers in a field setting, and in native soil under rainout shelters. In all three of these experiments, we collected leaf-level physiological and whole-genome gene expression data from droughted and control plants.Combined, the three experiments represent contrasts in drought experimental manipulations (i.e. the extent, timing, and duration of drought), plant characteristics (i.e. age, maturity, and size), and broadly fit with the concepts of best practice for physiological analysis of drought responses (Poorter et al., 2012b). Contrasting these experimental design considerations allows us to address how edaphic and climactic conditions impact links between gene expression and physiological phenotypic plasticity. Specifically, we assessed three fundamental questions pertaining to physiological genomics in the field: (1) How consistent is phenotypic plasticity to drought across experiments? (2) Which soil moisture deficit responses vary across sites, years, and timing of sampling? (3) How does plasticity of physiological and gene expression phenotypes covary within and across experiments? To assess these questions, we tested how leaf physiology and whole-genome gene expression responded to the effects of drought treatments, leaf water potential, and sampling time (midday and predawn). These analyses permitted inference of the number, relative effect size, and identity of differentially expressed (plastic) genes. Overall, our results suggested that differences in leaf water potential and diurnal patterns were the major drivers of gene expression variation. Furthermore, we observed consistent physiological plasticity across greenhouse dry-down and field precipitation manipulation experiments, but extreme variability in the number of differentially expressed genes.     

The dosage-mortality relationship for two strains of house flies exposed to vapor of di-isopropylphosphorofluoridate

The dosage-mortality relationship for normally susceptible and di-isopropylphosphorofluoridate (DFP)-resistantMusca domestica L. was determined by means of vapor exposures of varied durations and concentrations.With reference to concentration, males of either strain were approximately 1.5 × as sensitive as the respective females, and the strains differed by a factor of about 10. Probit kill at each concentration was proportional to log exposure time for all four groups, and the log of time required to kill half a given sex or strain (log Lt₅₀) was proportional to the log of DFP concentration. For all four groups the apparent order of toxic reaction was the same, — namely slightly more than 2.5.Since the actual toxic process probably is a bimolecular reaction between DFP and nervous system cholinesterase (ChE), the observations indicate that an appreciable portion of the entering DFP was diverted to nontoxic pathways. The data contain no suggestion that the sexes and strains are distinguished by any qualitative differences in these pathways. The differences in tolerance are significant but unexplained.With all four groups, like percentages of kill were accompanied on the average by like percentages of inhibition of head ChE despite considerable intergroup differences in the dosages required. Per cent inhibition was directly proportional to kill. The overall correlation observed corroborates the view that inhibition of central nervous system ChE is related causally to toxicity. In general, flies whose head ChE was inhibited less than about 50% did not succumb, while those with more than 50% inhibition died irrespective of their source and the dose of DFP needed.Although the relationship favors the conclusion that ChE inhibition is instrumental in the toxicity of DFP, it does not indicate that inhibition of head ChE is more than an indirect index of events at the as yet unknown true sites of action, nor that an acetylcholine-ChE mechanism of synaptic transmission is vitally involved in the functioning of insect nerve.

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Die Dosis-Mortalitäts-Benziehungen zweier Stubenfliegen-Stämme, die di-isopropulphosphorfluoridat-Dämpfen Ausgesetzt wurden

Zusammenfassung Wenn die Geschlechter zweier Stubenfliegen-Stämme (ein normal empfindlicher und ein DFP-resistenter) getrennt DFP-Dämpfen ausgesetzt wurden, waren die entsprechenden Reihen der log Lt₅₀ zwar verschieden, wurden jedoch in jedem Falle linear abhängig von der logarithmischen DFP-Konzentration und einander parallel befunden.Für alle vier Gruppen betrugen die erkennnbaren Werte der toxischen Reaktion etwas mehr als 2,5. Da die tatsächliche toxische Reaktion bimolokularer Kinetik zu gehorchen scheint, wird geschlossen, daß ein beträchtlicher Anteil des von den Fliegen absorbierten DFP in nicht-toxische Prozesse abgeleitet wird.Die Ergebnisse liefern keinerlei neue Erklärung der Toleranzunterschiede zwischen den Geschlechtern und Stämmen, und infolgedessen bleiben die Ursachen für diese Unterschiede unbekannt.Im Durchschnitt war die Hemmung der Cholinesterase des Kopfes direkt proportional zum Abtötungsprozentsatz, trotz des Vorliegens einer beträchtlichen Variabilität, welche zufallsmäßig war und offensichtlich auf inneren Faktoren beruht. In dieser Hinsicht bestanden keine signifikanten Unterschiede zwischen den Geschlechtern und Stämmen.Das beobachtete Verhältnis wird als strenger Beweis für ein kausale Beziehung zwischen Cholinesterase und Giftwirkung angesehen, jedoch wird der Grad der Kopf-Cholinesterase-Hemmung nur als Index für ein unbekanntes Ausmaß der Hemmung an anderen hypothetisch vitalen Punkten betrachtet. Die Befunde liefern weder Anhaltspunkte für noch wider die Auffassung, daß ein Acetylcholin-Cholinesterase-Mechanismus der synaptischen Übertragung eine vitale Funktion im Insekt besitzt.

     

Host genotype controls ecological change in the leaf fungal microbiome

Leaf fungal microbiomes can be fundamental drivers of host plant success, as they contain pathogens that devastate crop plants and taxa that enhance nutrient uptake, discourage herbivory, and antagonize pathogens. We measured leaf fungal diversity with amplicon sequencing across an entire growing season in a diversity panel of switchgrass (Panicum virgatum). We also sampled a replicated subset of genotypes across 3 additional sites to compare the importance of time, space, ecology, and genetics. We found a strong successional pattern in the microbiome shaped both by host genetics and environmental factors. Further, we used genome-wide association (GWA) mapping and RNA sequencing to show that 3 cysteine-rich receptor-like kinases (crRLKs) were linked to a genetic locus associated with microbiome structure. We confirmed GWAS results in an independent set of genotypes for both the internal transcribed spacer (ITS) and large subunit (LSU) ribosomal DNA markers. Fungal pathogens were central to microbial covariance networks, and genotypes susceptible to pathogens differed in their expression of the 3 crRLKs, suggesting that host immune genes are a principal means of controlling the entire leaf microbiome.

Leaf fungal microbiomes can strongly influence host plant success. Monitoring the leaf fungal microbiome of switchgrass over time shows microbial ecological succession, and reveals the host plant genes that influence community-wide changes.