THE EVOLUTION OF GENETIC CORRELATIONS: AN ANALYSIS OF PATTERNS

The genetic correlation is a central parameter of quantitative genetics, providing a measure of the rate at which traits respond to indirect selection (i.e., selection that does not act upon the traits under study, but some other trait with which they have genes in common). In this paper, I review the pattern of variation among four combinations of traits: life history × life history (L × L), morphological × morphological (M × M), life history × morphological (L × M), and behavioral × behavioral (B × B). A few other combinations were investigated, but insufficient data were obtained for separate analysis. A total of 1798 correlations, distributed over 51 different animal and plant species, were analyzed. The analysis was conducted at two levels: first by dividing the data set solely by trait combination, and second by blocking the data by trait combination and species. Because selection will tend to fix alleles that show positive correlations with fitness traits faster than those that are negative and because the latter are expected to arise more frequently by mutation, correlations between life-history traits are predicted to be more often negative than those between morphological traits. This prediction was supported, with the ranking in decreasing proportion of negative correlations being: L × L > L × M > B × B > M × M. The mean magnitude of the genetic correlation shows little variation among morphological and life-history combinations, and the distribution of values is remarkably flat. However, the estimated standard errors and the coefficient of variation (SE/r_G) are large, making it difficult to separate biological factors influencing the pattern of dispersion from experimental error. Analysis of the phenotypic and genetic correlations suggest that for the combinations M × M and L × M, but not L × L or B × B, the phenotypic correlation is an adequate estimate of the genetic correlation.     

Ascaris lumbricoides: succinate and tiglate in hemolymph

When hemolymph is taken from Ascaris lumbricoides at the time the worm is collected from pigs, it contains acetic, propionic, 2-methylbutyric, n-valeric, 2-methylvaleric, and succinic acid radicals; tiglic acid is absent.     

The benefits of interpopulation hybridization diminish with increasing divergence of small populations

Interpopulation hybridization can increase the viability of small populations suffering from inbreeding and genetic drift, but it can also result in outbreeding depression. The outcome of hybridization can depend on various factors, including the level of genetic divergence between the populations, and the number of source populations. Furthermore, the effects of hybridization can change between generations following the hybridization. We studied the effects of population divergence (low vs. high level of divergence) and the number of source populations (two vs. four source populations) on the viability of hybrid populations using experimental Drosophila littoralis populations. Population viability was measured for seven generations after hybridization as proportion of populations facing extinction and as per capita offspring production. Hybrid populations established at the low level of population divergence were more viable than the inbred source populations and had higher offspring production than the large control population. The positive effects of hybridization lasted for the seven generations. In contrast, at the high level of divergence, the viability of the hybrid populations was not significantly different from the inbred source populations, and offspring production in the hybrid populations was lower than in the large control population. The number of source populations did not have a significant effect at either low or high level of population divergence. The study shows that the benefits of interpopulation hybridization may decrease with increasing divergence of the populations, even when the populations share identical environmental conditions. We discuss the possible genetic mechanisms explaining the results and address the implications for conservation of populations.     

Nature of Novel 2D van der Waals Heterostructures for Superior Potassium Ion Batteries

Novel 2D van der Waals heterostructures with innovative bimetallic oxychloride (Bi‐ and Sb‐based oxychloride) nanosheets that are well dispersed on reduced graphene oxide nanosheets, are established through element engineering for superior potassium ion battery (PIBs) anodes. This material displays an exceptional electrochemical performance, obtaining a discharge capacity as high as 360 mAh g^?1 at 100 mA g^?1 after running 1000 cycles for over 9 months with a capacity preservation percentage of 88.5% and achieving a discharge capacity as high as 319 mAh g^?1 at 1000 mA g^?1, in addition to the low charge/discharge plateaus for anodes and promising full cell performance. More significantly, the nature of such 2D van der Waals heterostructures, including the element engineering for morphology control, the function of each component of heterostructures, the mechanism of potassium ion storage, and the process of K⁺ intercalation accompanied with the lattice distortion and chemical bond breakages, is explored in depth. This study is critical for not only paving the way for the practical application of PIBs but also shedding light on fundamentals of potassium ion storage in 2D van der Waals heterostructures.     

Senescence in cut carnation flowers: Temporal and physiological relationships among water status, ethylene, abscisic acid and membrane permeability

Changes in water status, membrane permeability, ethylene production and levels of abscisic acid (ABA) were measured during senescence of cut carnation flowers ( Dianthus caryophyllus L. cv. White Sim) in order to clarify the temporal sequence of physiological events during this post-harvest period. Ethylene production and ABA content of the petal tissue rose essentially in parallel during natural senescence and after treatment of young flowers with exogenous ethylene, indicating that their syntheses are not widely separated in time. However, solute leakage, reflecting membrane deterioration, was apparent well before the natural rise in ethylene and ABA had begun. In addition, there were marked changes in water status of the tissue, including losses in water potential (ψ_w), and turgor (ψ_p), that preceded the rise in ABA and ethylene. As senescence progressed, ψ_w continued to decline, but ψ_p returned to normal levels. These temporal relationships were less well resolved when senescence of young flowers was induced by treatment with ethylene, presumably because the time-scale had been shortened. Thus changes in membrane permeability and an associated water stress in petal tissue appear to be earlier symptoms of flower senescence than the rises in ABA or ethylene. These observations support the contention that the climacteric-like rise in ethylene production is not the initial or primary event of senescence and that the rise in ABA titre may simply be a response to changes in water status.     

Shewanella biofilm development and engineering for environmental and bioenergy applications

The genus Shewanella comprises about 70 species of Gram-negative, facultative anaerobic bacteria inhabiting various environments, which have shown great potential in various biotechnological applications ranging from environmental bioremediation, metal(loid) recovery and material synthesis to bioenergy generation. Most environmental and energy applications of Shewanella involve the biofilm mode of growth on surfaces of solid minerals or electrodes. In this article, we first provide an overview of Shewanella biofilm biology with the focus on biofilm dynamics, biofilm matrix, and key signalling systems involved in Shewanella biofilm development. Then we review strategies recently exploited to engineer Shewanella biofilms to improve biofilm-mediated bioprocesses.     

Electron Microscopic Evidence in Support of α-Solenoid Models of Proteasomal Subunits Rpn1 and Rpn2

Rpn1 (109 kDa) and Rpn2 (104 kDa) are components of the 19S regulatory complex of the proteasome. The central portions of both proteins are predicted to have toroidal α-solenoid folds composed of 9-11 proteasome/cyclosome repeats, each ∼ 40 residues long and containing two α-helices and turns [A. V. Kajava, J. Biol. Chem. 277, 49791-49798, 2002]. To evaluate this prediction, we examined the full-length yeast proteins and truncated versions thereof consisting only of the repeat-containing regions by gel filtration, CD spectroscopy, and negative-staining electron microscopy (EM). All four proteins are monomeric in solution and highly α-helical, particularly the truncated ones. The EM data were analyzed by image classification and averaging techniques. The preponderant projections, in each case, show near-annular molecules 6-7 nm in diameter. Comparison of the full-length with the truncated proteins showed molecules similar in size and shape, indicating that their terminal regions are flexible and thus smeared to invisibility in the averaged images. We tested the toroidal model further by calculating resolution-limited projections and comparing them with the EM images. The results support the α-solenoid model, except that they indicate that the repeats are organized not as symmetrical circular toroids but in less regular horseshoe-like structures.     

Antagonistic and synergistic interactions between aluminum and manganese on growth of Vigna unguiculata at low ionic strength

Concentrations of soluble aluminum (Al) and manganese (Mn) frequently reach phytotoxic levels in acid soils. While dose response relationships for these metals are well documented, the effects of combined exposure have received less attention. We have examined the effect of combinations of Al and Mn on growth and metal accumulation in Vigna unguiculata (L.) Walp. grown in solution culture under conditions of low ionic strength (conductivities typically < 100 µS cm⁻¹). The nature of interaction between these metals varied with the specific physiological response, the part of the plant investigated, and the relative amount of stress imposed. Analysis of growth data provided evidence for amelioration of metal toxicity (antagonistic effects), although this effect was dose dependent. Analysis of metal content data provided evidence for antagonistic and synergistic (exacerbation of toxicity) effects, again depending on dose. Analysis of foliar symptoms also provided evidence for antagonisms and synergisms, with the nature of the response dependent on the specific physiological response and specific plant part investigated. In contrast with previous reports, evidence for antagonistic, synergistic, and multiplicative effects on growth, metal uptake, and expression of foliar symptoms have been obtained under physiologically and environmentally relevant conditions. These results suggest a more detailed analysis of the potential for interactions between metals in the environment is required.