Floral volatiles with colour cues from two cucurbitaceous plants causing attraction of Aulacophora foveicollis

Aulacophora foveicollis Lucas (Coleoptera: Chrysomelidae) is an important phytophagous pest of two cucurbitaceous plants, Momordica cochinchinensis Spreng and Solena amplexicaulis (Lam.) Gandhi. The volatile organic compound profiles from flowers of M. cochinchinensis and S. amplexicaulis were identified and quantified by gas chromatography‐mass spectrometry (GC‐MS) and GC‐flame ionization detector (FID) analyses. Twenty nine and 28 compounds were identified in volatiles of M. cochinchinensis and S. amplexicaulis flowers, respectively. Methyl jasmonate and 3‐octanol were the predominant volatiles of M. cochinchinensis flowers, whereas 1‐octadecanol and 1‐hexanol were most found in the headspace of S. amplexicaulis flowers. Aulacophora foveicollis were more attracted by the flower volatiles of M. cochinchinensis than by those of S. amplexicaulis in a glass Y‐tube olfactometer. A mixture of 1‐heptanol, linalool oxide, 1‐octanol, and nonanal in the proportions present in the headspace of both flower types elicited attraction in the insect. From 25 cm distance, A. foveicollis displayed a preference for artificial flowers of 6.5 cm diameter of S. amplexicaulis flower colour (white) over M. cochinchinensis flower colour (white‐yellow). Finally, a synthetic blend (0.43 μg 1‐heptanol + 1.44 μg linalool oxide + 0.14 μg 1‐octanol + 1.77 μg nonanal dissolved in 25 μl methylene chloride) attracted more beetles when applied in a white artificial flower than when applied in a white‐yellow artificial flower from 40 cm distance. This finding may be helpful in the development of traps for pest management strategies.     

Hox2 Genes Are Required for Tonotopic Map Precision and Sound Discrimination in the Mouse Auditory Brainstem

1. Download high-res image (303KB)
2. Download full-size image

     

Extra‐mitochondrial localization and likely reproductive function of a female‐transmitted cytochrome c oxidase subunit II protein

Our previous study documented a reproductive function for the male‐transmitted mitochondrial DNA (mtDNA)‐encoded cytochrome c oxidase subunit II (MCOX2) protein in a unionoid bivalve. Here, immunoblotting, immunohistochemistry and immunoelectron microscopy analyses demonstrate that the female‐transmitted protein (FCOX2) is: (i) expressed in both male and female gonads; (ii) maximally expressed in ovaries just prior to the time of the annual fertilization event; (iii) displayed in the cytoplasm and more strongly in the plasma membrane (microvilli), vitelline matrix and vitelline envelope of mature ovarian eggs; and (iv) strongly localized to the vitelline matrix of some eggs just prior to fertilization. These findings represent evidence for the extra‐mitochondrial localization of an mtDNA‐encoded gene product and are consistent with multifunctionality for FCOX2 in eggs.     

Structural basis for the hyperthermostability of an archaeal enzyme induced by succinimide formation

Stability of proteins from hyperthermophiles (organisms existing under boiling water conditions) enabled by a reduction of conformational flexibility is realized through various mechanisms. A succinimide (SNN) arising from the post-translational cyclization of the side chains of aspartyl/asparaginyl residues with the backbone amide -NH of the succeeding residue would restrain the torsion angle Ψ and can serve as a new route for hyperthermostability. However, such a succinimide is typically prone to hydrolysis, transforming to either an aspartyl or β-isoaspartyl residue. Here, we present the crystal structure of Methanocaldococcus jannaschii glutamine amidotransferase and, using enhanced sampling molecular dynamics simulations, address the mechanism of its increased thermostability, up to 100°C, imparted by an unexpectedly stable succinimidyl residue at position 109. The stability of SNN109 to hydrolysis is seen to arise from its electrostatic shielding by the side-chain carboxylate group of its succeeding residue Asp110, as well as through n → π¹ interactions between SNN109 and its preceding residue Glu108, both of which prevent water access to SNN. The stable succinimidyl residue induces the formation of an α-turn structure involving 13-atom hydrogen bonding, which locks the local conformation, reducing protein flexibility. The destabilization of the protein upon replacement of SNN with a Φ-restricted prolyl residue highlights the specificity of the succinimidyl residue in imparting hyperthermostability to the enzyme. The conservation of the succinimide-forming tripeptide sequence (E(N/D)(E/D)) in several archaeal GATases strongly suggests an adaptation of this otherwise detrimental post-translational modification as a harbinger of thermostability.     

Evolution of human immunodeficiency virus type 1 cytotoxic T-lymphocyte epitopes: fitness-balanced escape

CD8(+) cytotoxic T lymphocytes (CTL) are strong mediators of human immunodeficiency virus type 1 (HIV-1) control, yet HIV-1 frequently mutates to escape CTL recognition. In an analysis of sequences in the Los Alamos HIV-1 database, we show that emerging CTL escape mutations were more often present at lower frequencies than the amino acid(s) that they replaced. Furthermore, epitopes that underwent escape contained amino acid sites of high variability, whereas epitopes persisting at high frequencies lacked highly variable sites. We therefore infer that escape mutations are likely to be associated with weak functional constraints on the viral protein. This was supported by an extensive analysis of one subject for whom all escape mutations within defined CTL epitopes were studied and by an analysis of all reported escape mutations of defined CTL epitopes in the HIV Immunology Database. In one of these defined epitopes, escape mutations involving the substitution of amino acids with lower database frequencies occurred, and the epitope soon reverted back to the sensitive form. We further show that this escape mutation substantially diminished viral fitness in in vitro competition assays. Coincident with the reversion in vivo, we observed the fixation of a mutation 3 amino acids C terminal to the epitope, coincident with the ablation of the corresponding CTL response. The C-terminal mutation did not restore replication fitness reduced by the escape mutation in the epitope and by itself had little effect on replication fitness. Therefore, this C-terminal mutation presumably impaired the processing and presentation of the epitope. Finally, for one persistent epitope, CTL cross-reactivity to a mutant form may have suppressed the mutant to undetected levels, whereas for two other persistent epitopes, each of two mutants showed poor cross-reactivity and appeared in the subject at later time points. Thus, a viral dynamic exists between the advantage of immune escape, peptide cross-reactivity, and the disadvantage of lost replication fitness, with the balance playing an important role in determining whether a CTL epitope will persist or decline during infection.     

Quantitative palmar dermatoglyphics and the assessment of population affinities: data from marine fishermen of Puri, India

Variation in quantitative dermatoglyphics among three endogamous groups of marine fishermen of Puri Coast, India, is greater for the palmar variables than for the fingers. This is the case in both the sexes. The pattern of population affinities, however, differs for the males and females. In order to evaluate the importance of palmar variables in population studies, the results in males are compared with those of finger variables and anthropometrics. There is no significant heterogeneity between the groups for finger variables. Although significant intergroup variability is observed in the palmar and anthropometric traits, the two sets of results are not in the same direction. Palmar dermatoglyphic relationships reflect the caste affiliations, while the anthropometric are in line with geographic proximity.     

PCA based population generation for genetic network optimization

A gene regulatory network (GRN) represents a set of genes and its regulatory interactions. The inference of the regulatory interactions between genes is usually carried out using an appropriate mathematical model and the available gene expression profile. Among the various models proposed for GRN inference, our recently proposed Michaelis–Menten based ODE model provides a good trade-off between the computational complexity and biological relevance. This model, like other known GRN models, also uses an evolutionary algorithm for parameter estimation. Considering various issues associated with such population based stochastic optimization approaches (e.g. diversity, premature convergence due to local optima, accuracy, etc.), it becomes important to seed the initial population with good individuals which are closer to the optimal solution. In this paper, we exploit the inherent strength of principal component analysis (PCA) in a novel manner to initialize the population for GRN optimization. The benefit of the proposed method is validated by reconstructing in silico and in vivo networks of various sizes. For the same level of accuracy, the approach with PCA based initialization shows improved convergence speed.     

Werner syndrome protein interacts with human flap endonuclease 1 and stimulates its cleavage activity

Werner syndrome (WS) is a human premature aging disorder characterized by chromosomal instability. The cellular defects of WS presumably reflect compromised or aberrant function of a DNA metabolic pathway that under normal circumstances confers stability to the genome. We report a novel interaction of the WRN gene product with the human 5' flap endonuclease/5'-3' exonuclease (FEN-1), a DNA structure-specific nuclease implicated in DNA replication, recombination and repair. WS protein (WRN) dramatically stimulates the rate of FEN-1 cleavage of a 5' flap DNA substrate. The WRN-FEN-1 functional interaction is independent of WRN catalytic function and mediated by a 144 amino acid domain of WRN that shares homology with RecQ DNA helicases. A physical interaction between WRN and FEN-1 is demonstrated by their co-immunoprecipitation from HeLa cell lysate and affinity pull-down experiments using a recombinant C-terminal fragment of WRN. The underlying defect of WS is discussed in light of the evidence for the interaction between WRN and FEN-1.