Resistance to glufosinate is proportional to phosphinothricin acetyltransferase expression and activity in LibertyLink® and WideStrike® cotton

Planta - Insertion of the gene encoding phosphinothricin acetyltransferase (PAT) has resulted in cotton plants resistant to the herbicide glufosinate. However, the lower expression and commensurate...     

Do We Need to Detect Isoniazid Resistance in Addition to Rifampicin Resistance in Diagnostic Tests for Tuberculosis?

Background

Multidrug-resistant tuberculosis (MDR-TB) is resistant to both rifampicin (RIF) and isoniazid (INH). Whereas many TB diagnostics detect RIF-resistance, few detect INH-monoresistance, which is common and may increase risk of acquired MDR-TB. Whether inclusion of INH-resistance in a first-line rapid test for TB would have an important impact on MDR-TB rates remains uncertain.

Methods

We developed a transmission model to evaluate three tests in a population similar to that of India: a rapid molecular test for TB, the same test plus RIF-resistance detection (“TB+RIF”), and detection of RIF and INH-resistance (“TB+RIF/INH”). Our primary outcome was the prevalence of INH-resistant and MDR-TB at ten years.

Results

Compared to the TB test alone and assuming treatment of all diagnosed MDR cases, the TB+RIF test reduced the prevalence of MDR-TB among all TB cases from 5.5% to 3.8% (30.6% reduction, 95% uncertainty range, UR: 17–54%). Despite using liberal assumptions about the impact of INH-monoresistance on treatment outcomes and MDR-TB acquisition, expansion from TB+RIF to TB+RIF/INH lowered this prevalence only from 3.8% to 3.6% further (4% reduction, 95% UR: 3–7%) and INH-monoresistant TB from 15.8% to 15.1% (4% reduction, 95% UR: (-8)-19%).

Conclusion

When added to a rapid test for TB plus RIF-resistance, detection of INH-resistance has minimal impact on transmission of TB, MDR-TB, and INH-monoresistant TB.     

Resistance of α-globulin fromSesamum indicum L. to proteases in relationship to its structure

α-Globulin, the high-molecular-weight protein fraction fromSesamum indicum L., was hydrolyzed to low-molecular-weight protein and peptides by pepsin, while its resistance to hydrolysis by group-specific enzymes, trypsin or α-chymotrypsin, was very high. The protein showed definite structural changes after proteolysis, especially after peptic hydrolysis, as evidenced from various biophysical data. The sedimentation velocity pattern of α-globulin hydrolyzed by trypsin or α-chymotrypsin indicated reduction in the percentage of 11S component, while the pepsinhydrolyzed sample was devoid of any 11S component, indicating the absence of a native protein molecule. The fluorescence emission spectra of the various hydrolyzed α-globulin showed a red shift in the fluorescence emission maximum. The red shift was maximum with α-globulin hydrolyzed by pepsin and minimum with the trypsin-hydrolyzed sample. The far-ultraviolet-circular dichroic measurements indicated that most of the ordered structure of α-globulin was absent after pepsin hydrolysis, while after trypsin and chymotrypsin hydrolysis conformational changes were less.     

Genetic Analysis of Resistance to Benzimidazoles in Physarum: Differential Expression of β-Tubulin Genes

Physarum displays two vegetative cell types, uninucleate myxamoebae and multinucleate plasmodia. Mutant myxamoebae of Physarum resistant to the antitubulin drug methylbenzimidazole-2-yl-carbamate (MBC) were isolated. All mutants tested were cross-resistant to other benzimidazoles but not to cycloheximide or emetine. Genetic analysis showed that mutation to MBC resistance can occur at any one of four unlinked loci, benA, benB, benC or benD. MBC resistance of benB and benD mutants was expressed in plasmodia, but benA and benC mutant plasmodia were MBC sensitive, suggesting that benA and benC encode myxamoeba-specific products. Myxamoebae carrying the recessive benD210 mutation express a β-tubulin with noval electrophoretic mobility, in addition to a β-tubulin with wild-type mobility. This and other evidence indicates that benD is a structural gene for β-tubulin, and that at least two β-tubulin genes are expressed in myxamoebae. Comparisons of the β-tubulins of wildtype and benD210 strains by gel electrophoresis revealed that, of the three (or more) β-tubulin genes expressed in Physarum, one, benD, is expressed in both myxamoebae and plasmodia, one is expressed specifically in myxamoebae and one is expressed specifically in plasmodia. However, mutation in only one gene, benD, is sufficient to confer MBC resistance on both myxamoebae and plasmodia.     

Resistance to gastrointestinal parasite infection in Djallonké sheep

Gastrointestinal parasitism places serious constraints on small ruminant production. The situation has been exacerbated by development of drug resistance in many parasite populations, leading to interest in identification of animals with genetically mediated resistance or tolerance to nematode infections. This study assessed the response to natural infection with gastrointestinal nematodes (GIN) in Djallonké sheep during the rainy season in the Sudan-Guinea Savannah region of Burkina Faso. Haemonchus contortus is the most prevalent GIN at this site and time. Djallonké lambs (n=434) were sampled from 40 households and evaluated at a common location in southern Burkina Faso. Lambs were dewormed with levamisole at 2 to 6 months of age and returned to infected pastures. Fecal egg counts (FEC), packed cell volumes (PCV), and FAffa Malan CHArt (FAMACHA©) scores were determined 28 and 35 days after deworming. Lamb mortality was monitored throughout the experiment. Least-squares means for BW increased from 13.8±0.2 kg at 28 days to 14.0±0.2 kg at 35 days (P<0.01). Simple means and medians for FEC were 615 and 100, respectively, at 28 days and 850 and 175, respectively, at 35 days. The FEC exhibited strong right skewness. Following logarithmic transformation and back-transformation of resulting least-squares means to the original scale, FEC were higher (P<0.01) for males (208±27) than females (122±10). Least-squares means for PCV decreased (P<0.001) from 28 (36.3±0.5%) to 35 days (33.7±0.5%), and were higher (P<0.01) for females (36.0±0.4%) than males (33.9±0.7%). Correlations (r) between repeated measurements of BW, FEC, PCV and FAMACHA scores at 28 and 35 days were all positive (P<0.001). The correlation between FAMACHA scores and PCV was negative at 28 (r=−0.14) and 35 days (r=−0.18) (P<0.001). This study revealed that BW was an easily measured predictor of the ability of the lamb to resist infection with GIN and maintain PCV, and confirmed that FAMACHA scores are useful indicators of differences in FEC. Approximately 40% of female and 30% of male lambs did not show detectable levels of infection (i.e. FEC=0) under field conditions. The great variability that was observed in FEC and PCV suggests potential to use Djallonké sheep in breeding programs to enhance resistance to GIN.     

Resistance of α-globulin fromSesamum indicum L. to proteases in relationship to its structure

-Globulin, the high-molecular-weight protein fraction fromSesamum indicum L., was hydrolyzed to low-molecular-weight protein and peptides by pepsin, while its resistance to hydrolysis by group-specific enzymes, trypsin or -chymotrypsin, was very high. The protein showed definite structural changes after proteolysis, especially after peptic hydrolysis, as evidenced from various biophysical data. The sedimentation velocity pattern of -globulin hydrolyzed by trypsin or -chymotrypsin indicated reduction in the percentage of 11S component, while the pepsinhydrolyzed sample was devoid of any 11S component, indicating the absence of a native protein molecule. The fluorescence emission spectra of the various hydrolyzed -globulin showed a red shift in the fluorescence emission maximum. The red shift was maximum with -globulin hydrolyzed by pepsin and minimum with the trypsin-hydrolyzed sample. The far-ultraviolet-circular dichroic measurements indicated that most of the ordered structure of -globulin was absent after pepsin hydrolysis, while after trypsin and chymotrypsin hydrolysis conformational changes were less.     

Resistance of α-crystallin quaternary structure to UV irradiation

The damaging effect of UV radiation (λ > 260 nm) on bovine α-crystallin in solution was studied by small-angle X-ray scattering, gel permeation chromatography, electrophoresis, absorption and fluorescence spectroscopy, and differential scanning calorimetry. The results obtained show that damage to even a large number of subunits within an α-crystallin oligomer does not cause significant rearrangement of its quaternary structure, aggregation of oligomers, or the loss of their solubility. Due to the high resistance of its quaternary structure, α-crystallin is able to prevent aggregation of destabilized proteins (especially of γ- and β-crystallins) and so to maintain lens transparency throughout the life of an animal (the chaperone-like function of α-crystallin).     

Introduction to plenary papers

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Reproductive toxicity of BioThrax® in rabbits

BACKGROUND: An increasing number of women are being vaccinated during child-bearing years, including vaccination with BioThrax^® (Anthrax Vaccine Adsorbed, or AVA). As only a limited number of studies exist in humans that have examined the effects of AVA on reproductive health, this study was conducted in order to evaluate the impact AVA vaccination may have on pregnant female rabbits and their offspring. METHODS: Two hundred female rabbits were vaccinated with saline, adjuvant, or AVA twice prior to mating and on one of two occasions during gestation, in order to have exposure to the antigen during organogenesis. Blood samples were collected from does and fetuses/kits to assess the development and in utero transfer of antibodies to Bacillus anthracisprotective antigen (anti-PA IgG). Half of the does underwent Caesarean-sectioning on gestation day 29 and a gross necropsy was performed on both the does and their fetuses. The other half were allowed to naturally deliver and gross necropsy of the does and their kits was performed on lactation day 29. RESULTS: ELISA results showed that anti-PA IgG was generated by the does and passed to the fetuses/kits at detectable levels. CONCLUSIONS: AVA directly, or indirectly through the production of anti-PA IgG, did not appear to have an adverse effect on the pregnant females or their offspring, as measured by mating and fertility indices, natural delivery observations, clinical signs, gross lesions, in utero growth and survival, morphological development, or kit viability. Birth Defects Res (Part B) 86:370–376, 2009. © 2009 Wiley-Liss, Inc.     

Implication of Porins in β-Lactam Resistance of Providencia stuartii

An integrative approach combining biophysical and microbiological methods was used to characterize the antibiotic translocation through the outer membrane of Providencia stuartii. Two novel members of the General Bacterial Porin family of Enterobacteriaceae, named OmpPst1 and OmpPst2, were identified in P. stuartii. In the presence of ertapenem (ERT), cefepime (FEP), and cefoxitin (FOX) in growth media, several resistant derivatives of P. stuartii ATCC 29914 showed OmpPst1-deficiency. These porin-deficient strains showed significant decrease of susceptibility to β-lactam antibiotics. OmpPst1 and OmpPst2 were purified to homogeneity and reconstituted into planar lipid bilayers to study their biophysical characteristics and their interactions with β-lactam molecules. Determination of β-lactam translocation through OmpPst1 and OmpPst2 indicated that the strength of interaction decreased in the order of ertapenem ≫ cefepime > cefoxitin. Moreover, the translocation of these antibiotics through OmpPst1 was more efficient than through OmpPst2. Heterologous expression of OmpPst1 in the porin-deficient E. coli strain BL21(DE3)omp8 was associated with a higher antibiotic susceptibility of the E. coli cells to β-lactams compared with expression of OmpPst2. All our data enlighten the involvement of porins in the resistance of P. stuartii to β-lactam antibiotics.     

Fluoroquinolone Resistance Linked to Both gyrA and parC Mutations in the Quinolone Resistance–Determining Region of Shigella dysenteriae Type 1

We examined the quinolone resistance–determining region (QRDR) of gyrA, gyrB, and parC of recently isolated fluoroquinolone-resistant S. dysenteriae type 1 strains from south Asia and compared data with fluoroquinolone-susceptible strains associated with previous epidemics of 1978, 1984, and 1994. In fluoroquinolone-resistant strains, double mutations (Ser⁸³ → Leu, Asp⁸⁷ → Asn or Gly) and a single mutation (Ser⁸⁰ → Ile) were detected in the QRDRs of gyrA and parC, respectively.     

Inheritance and Gene Mapping of Resistance to Soybean Mosaic Virus Strain SC14 in Soybean

Soybean mosaic virus (SMV) is one of the most broadly distributed diseases worldwide. It causes severe yield loss and seed quality deficiency in soybean (Glycine max (L.) Merr.). SMV Strain SC14 isolated from Shanxi Province, China, was a newly identified virulent strain and can infect Kefeng No. 1, a source with wide spectrum resistance. In the present study, soybean accessions, PI96983, Qihuang No. 1 and Qihuang No. 22 were identified to be resistant (R) and Nannong 1138‐2, Pixianchadou susceptible (S) to SC14. Segregation analysis of PI96983 x Nannong 1138‐2 indicated that a single dominant gene (designated as R_SC14) controlled the resistance to SC14 at both V₂ and R₁ developmental stages. The same results were obtained for the crosses of Qihuang No. 1 × Nannong 1138‐2 and Qihuang No. 22 × Nannong 1138‐2 as in PI96983 × Nannong 1138‐2 at V₂ stage, but at R₁ stage, the F₁ performed as necrosis (a susceptible symptom other than mosaic), F₂ segregated in a ratio of 1R:2N:1S, and the progenies of necrotic (N) F₂ individuals segregated also in R, N and S. It indicated that a single gene (designated as R_SC14Q, to be different from that of PI96983) controlled the resistance to SC14, its dominance was the same as in PI96983 × Nannong 1138‐2 (without symptoms) at V₂ stage and not the same at R₁ stage. The tightly linked co‐dominant simple sequence repeat (SSR) marker Satt334 indicated that all the heterozygous bands were completely corresponding to the necrotic F₂ individuals, or all the necrotic F₂ individuals were heterozygotes. It was inferred that necrosis might be due to the interaction among SMV strains, resistance genes, genetic background of the resistance genes, and plant development stage. Furthermore, the bulked segregant analysis (BSA) of SSR markers was conducted to map the resistance genes. In F2of PI96983 × Nannong 1138‐2, five SSR markers, Sat_297, Sat_234, Sat_154, Sct_033 and Sat_120, were found closely linked to RSC14, with genetic distances of 14.5 cM, 11.3cM, 4.3cM,3.2cM and 6cM, respectively. In F₂ of Qihuang No. 1 × Nannong 1138‐2, three SSR markers, Sat_234, Satt334 and Sct_033, tightly linked to R_SC14Q with genetic distances of 7.2 cM, 1.4 cM and 2.8 cM, respectively. Based on the integrated joint map by Cregan et al. (1999), both RScMand R_SC14Q were located between Sat_234 and Sct_033 on linkage with group F of soybean, with their distances from Sct_033 at the same side being 3.2 cM and 2.8 cM, respectively. Therefore, RSC14and R_SC14Q might be on a same locus. The obtained information provides a basic knowledge for marker‐assisted selection of the resistance gene in soybean breeding programs and fine mapping and map‐based cloning of the resistance gene. (Managing editor: Li‐Hui Zhao)