Conditions for the validity of SNP-based heritability estimation

The heritability of a trait (h ²) is the proportion of its population variance caused by genetic differences, and estimates of this parameter are important for interpreting the results of genome-wide association studies (GWAS). In recent years, researchers have adopted a novel method for estimating a lower bound on heritability directly from GWAS data that uses realized genetic similarities between nominally unrelated individuals. The quantity estimated by this method is purported to be the contribution to heritability that could in principle be recovered from association studies employing the given panel of SNPs ( \(h_{\text{SNP}}^{2}\) ). Thus far, the validity of this approach has mostly been tested empirically. Here, we provide a mathematical explication and show that the method should remain a robust means of obtaining \(h_{\text{SNP}}^{2}\) under circumstances wider than those under which it has so far been derived.     

Patterns of genetic parameters for height in field genetic tests of Picea abies and Pinus sylvestris in Sweden

We reviewed the genetic parameter estimates carried out from 1992 to 2006 for height increment in genetic tests of Norway spruce and Scots pine, to describe patterns of genetic variation, heritability, and genetic correlations. The material included seedling and clonal tests in Sweden, aged between 5 and 20 years. Multiple regression was used to explore relationships between parameter values and test environments. Results showed moderate narrow-sense heritabilities ([^(h)]² {\hat{h}^2} : mean =0.29 in Norway spruce; mean =0.23 in Scots pine) that decreased with test site latitude for both species. In Norway spruce, [^(h)]² {\hat{h}^2} increased with better growth and decreased with tree age, while for Scots pine, [^(h)]² {\hat{h}^2} increased with tree age and southward transfer. The additive genetic coefficient of variation (; mean 15%), in Norway spruce, decreased with growth as well as site latitude. in Scots pine (mean =8.5%) increased with southward transfer and more southerly test latitude. Additive and genotypic within-site genetic age-age correlations in Norway spruce were high, with mean r _A and r _G of 0.92 and 0.85, respectively. Corresponding across-sites estimates were on average lower. Genetic parameters were better expressed on favorable sites, at younger ages in Norway spruce and at older ages in Scots pine. The results imply that gain calculations should be based on different parameters in the two species. For maximizing genetic gain in the Swedish breeding program, testing times could be shorter for Norway spruce than for Scots pine. The investigation showed a large variation in parameter estimates from different field experiments, highlighting the importance of testing over multiple sites.     

Fine-scale spatial genetic structure and allozymic diversity in natural populations of <Emphasis Type="Italic">Ocotea catharinensis</Emphasis> Mez. (Lauraceae)

In order to establish a strategy for conservation, the distribution of genetic diversity in four natural populations of Ocotea catharinensis in the Brazilian Atlantic rain forest was investigated using 18 allozyme loci. Estimates of the average number of alleles per loci (2.2), percentage of polymorphic loci (83.3%) and expected genetic diversity (0.427) in adult individuals were high; suggesting that all populations have genetic potential for conservation. The inbreeding within populations ([^(f)] = - 0.0 1 1 \hat{f} = - 0.0 1 1 ) and the total inbreeding ([^(F)] = 0. 1 3 3 \hat{F} = 0. 1 3 3 ) suggest population structure, since a high level of divergence among populations ( [^(q)]_\textP = 0. 1 4 3 \hat{\theta }_{\text{P}} = 0. 1 4 3 ) was also detected. Significant values of spatial genetic structure were found inside the four populations. This study demonstrates that the realized gene flow among the remaining populations of O. catharinensis is not sufficient to stop population divergence due to genetic drift and local selection, which threatens the future viability of this species.     

Courtship in the Zig-Zag Salamander (Plethodon dorsalis): Insights into a Transition in Pheromone-Delivery Behavior

Courtship in plethodontid salamanders includes the delivery of male courtship pheromones by two distinct modes. Within the eastern Plethodon clade of the tribe Plethodontini, members of the Plethodon cinereus species group use an ancestral ‘vaccination’ mode of delivery, while members of the P. glutinosus group use an olfactory delivery mode. In order to shed light on this transition in delivery mode, I observed courtship behavior in P. dorsalis, a species that is phylogenetically intermediate to the P. cinereus and P. glutinosus groups. My observations indicate that P. dorsalis also is intermediate to the P. cinereus and P. glutinosus species groups in terms of courtship behavior. The context of delivery of male courtship pheromones in P. dorsalis is similar to that of the P. cinereus species group; however, the mode of pheromone delivery in P. dorsalis is olfactory. Thus, a transition in the context of pheromone delivery underlies the more obvious change in pheromone delivery mode. I discuss these findings in terms of the evolution of courtship pheromone delivery across the eastern Plethodon clade. I also report the first observations of ‘premature’ spermatophore deposition by male plethodontids.     

Genetic diversity,genetic drift and mixed mating system in small subpopulations of <Emphasis Type="Italic">Dyckia ibiramensis</Emphasis>, a rare endemic bromeliad from Southern Brazil

Dyckia ibiramensis is a naturally rare, endemic and threatened bromeliad which occurs naturally on 4 km of rocky river outcroppings in Southern Brazil. For this study, subpopulations of the species were characterized based on size and genetics, to compile information for in situ and ex situ conservation strategies. A census of the rosettes was undertaken for each subpopulation and seven allozyme polymorphic loci were used to estimate genetic diversity and structure of adults and offspring and assess the mating system. In general, the subpopulations were small and most of the rosettes were aggregated into clumps. The species showed a high genetic diversity ([^(H)]_e = 0.219 \hat{H}_{e} = 0.219 ) and significant fixation index ([^(f)] = 0.642, \hat{f} = 0.642, P ≤ 0.05). The estimate of differentiation among all adult subpopulations indicate pronounced genetic structure ([^(G)]^￠_ST = 0.674 \hat{G}^{\prime}_{ST} = 0.674 ). D. ibiramensis has a mixed mating system and multilocus outcrossing rates [^(t)]_m \hat{t}_{m} were variable between subpopulations. This study demonstrates the importance of in situ preservation of all subpopulations for the maintenance of species diversity. For effective ex situ conservation, it would be necessary to collect seeds from 52 to 99 seed-rosettes, depending on the target population.     

Genetic parameters and predicted selection responses for timber production traits in a Castanea sativa progeny trial: developing a breeding program

Total height, diameter, index volume, stem straightness, apical dominance, and survival were assessed at 8 years from seed in an open-pollinated progeny test of 36 families of European chestnut (Castanea sativa Miller) established at two sites in the Atlantic area of Galicia, Spain. Iterative spatial analysis was applied to eliminate the effect of the spatial dependence in the original data and to estimate accurately genetic parameters for evaluating the potential for selection of the measured trees. Spatial analysis was very beneficial for growth traits and survival, but less so if at all for form traits. Estimated individual heritabilities ranged from moderate to high for growth traits ([^(h)]_i² = 0.29 - 0.42 \widehat{h}_i^2 = 0.29 - 0.42 ) and stem straightness ([^(h)]_i² = 0.24 - 0.42 \widehat{h}_i^2 = 0.{24} - 0.{42} ). High coefficients of additive genetic variance were obtained for volume ( [^(\textC)]\textV_\textA = 36.5 - 41.5% \widehat{\text{C}}{{\text{V}}_{\text{A}}} = {36}.{5} - {41}.{5}\% ) and straightness ( [^(\textC)]\textV_\textA = 44.26 - 53.84% \widehat{\text{C}}{{\text{V}}_{\text{A}}} = {44}.{26} - {53}.{84}\% ). Phenotypic and estimated genetic correlations between growth traits were very high, and correlations between sites indicated that there was no important family × site interaction. No adverse correlations between traits were evident. The results indicate the ample potential for selection in the current progeny trial, where responses to within-family and combined selection for growth traits may be high. Accordingly, three selection scenarios were addressed with the aim to initiate the selection of individuals for implementing the Forest Breeding Plan of Galicia for European chestnut.     

Growth yields and saturation constant of Desulfovibrio vulgaris in chemostat culture

Desulfovibrio vulgaris (strain Marburg) was grown on H₂ and sulfate as sole energy source in a chemostat limited by the sulfate supply. The biomass concentration and the sulfate concentration in the culture were determined as a function of the dilution rate. From the data a K _S (saturation constant) for sulfate of 10 M, a _max of 0.23 h^–1, and a of 13 g/mol were calculated. The organism was also grown in chemostat culture on H₂ and sulfite, H₂ and thiosulfate, and pyruvate (without sulfate). was found to be 35 g/mol, 36 g/mol, and Y _pyr ^max 10 g/mol. The growth yields are discussed with respect to ATP gains in dissimilatory sulfate reduction.     

Bayesian estimation of genetic parameters for growth,stem straightness,and survival in Eucalyptus globulus on an Andean Foothill site

Knowledge of the genetic variation of key economic traits in Eucalyptus globulus under cold conditions is crucial to the genetic improvement of environmental tolerances and other economic traits. A Bayesian analysis of genetic parameters for quantitative traits was carried out in 37 E. globulus open-pollinated families under cold conditions in southern Chile. The trial is located in the Andean foothills, in the Province of Bío-Bío. The Bayesian approach was performed using Gibbs sampling algorithm. Multi-trait linear and threshold models were fitted to phenotypic data (growth traits, survival, and stem straightness). Fifteen years after planting, height, diameter at breast height, and stem volume were found to be weakly to moderately heritable with Bayesian credible intervals (probability of 90 %): $ {\widehat{h}}^2 $ ?=?0.009–0.102, $ {\widehat{h}}^2 $ ?=?0.031–0.185, and $ {\widehat{h}}^2 $ ?=?0.045–0.205, respectively. Stem straightness was found to be weakly to moderately heritable ranging from 0.032 to 0.208 (Bayesian 90 % credible interval); posterior mode $ {\widehat{h}}^2 $ ?=?0.091. Tree survival at age of 15 years was high in the trial (84.8 %) with such heritability values ranging from 0.072 to 0.157. Survival was non-significantly genetically correlated to growth and stem straightness. Stem volume had the highest predicted genetic gains ranging from 17.9 to 23.7 % (selection rate of 15.8 and 8.3 %, respectively). The results of this study confirm the potential for selective breeding of this eucalypt in areas of southern Chile where cold is a significant constraint.     

Heritability for resistance to Puccinia psidii Winter rust in Eucalyptus grandis Hill ex Maiden in Southwestern Brazil

The climates of the central and southern regions of São Paulo state in Brazil favor pathogens such as Puccinia psidii Winter, which causes a common and severe disease in Eucalyptus plantations under 2 years old. We studied genetic parameters including genotype by environment interaction (G × E) of resistance to P. psidii rust in Eucalyptus grandis at nine sites in São Paulo State. Open-pollinated progeny from ten ‘provenances’ were established in a randomized complete block design; at individual sites there were from 134 to 160 progenies, from four to eight blocks, and five to six trees per plot. Significant provenance and progeny(provenance) differences were detected, as was G × E involving progeny(provenance). However, the G × E involved little if any rank changes, indicating that selection can be done efficiently at a single site, if the disease level is sufficient. The estimated coefficient of genetic variation among the progeny within provenances $ \left( {{{{\widehat{\mathrm{CV}}}}_{\mathrm{g}}}} \right) $ was high and variable among the sites (ranging from 11 % to 36.7 %), demonstrating different expression of genetic variability among the sites. The estimated heritability at the individual-tree level $ \left( {{{\widehat{h}}^2}} \right) $ and within a plot $ \left( {\widehat{h}_{\mathrm{w}}^2} \right) $ ranged from low to intermediate (ranging from 0.04 to 0.46) and was high at the progeny-mean level $ \left( {\widehat{h}_{\mathrm{f}}^2} \right) $ (ranging from 0.30 to 0.86). Our study shows good prospects of controlling this disease by selection among and within progenies in a single site.     

Loss of ncm<Superscript>5</Superscript> and mcm<Superscript>5</Superscript> wobble uridine side chains results in an altered metabolic profile

Introduction

The Elongator complex, comprising six subunits (Elp1p-Elp6p), is required for formation of 5-carbamoylmethyl (ncm⁵) and 5-methoxycarbonylmethyl (mcm⁵) side chains on wobble uridines in 11 out of 42 tRNA species in Saccharomyces cerevisiae. Loss of these side chains reduces the efficiency of tRNA decoding during translation, resulting in pleiotropic phenotypes. Overexpression of hypomodified \( {\text {tRNA}_{{\rm s^{2} {\rm UUU}}}^{{\rm Lys}} , {\rm tRNA}_{{\rm s^{2} {\rm UUG}}}^{{\rm Gln }} \;{\rm and}\;{\rm tRNA}_{{\rm s^{2} {\rm UUC}}}^{{\rm Glu}}} \), which in wild-type strains are modified with mcm⁵s²U, partially suppress phenotypes of an elp3Δ strain.

Objectives

To identify metabolic alterations in an elp3Δ strain and elucidate whether these metabolic alterations are suppressed by overexpression of hypomodified \( {\text {tRNA}_{{\rm s^{2} {\rm UUU}}}^{{\rm Lys}} , {\rm tRNA}_{{\rm s^{2} {\rm UUG}}}^{{\rm Gln }} \;{\rm and}\;{\rm tRNA}_{{\rm s^{2} {\rm UUC}}}^{{\rm Glu}}} \).

Method

Metabolic profiles were obtained using untargeted GC-TOF-MS of a temperature-sensitive elp3Δ strain carrying either an empty low-copy vector, an empty high-copy vector, a low-copy vector harboring the wild-type ELP3 gene, or a high-copy vector overexpressing \( {\text {tRNA}_{{\rm s^{2} {\rm UUU}}}^{{\rm Lys}} , {\rm tRNA}_{{\rm s^{2} {\rm UUG}}}^{{\rm Gln }} \;{\rm and}\;{\rm tRNA}_{{\rm s^{2} {\rm UUC}}}^{{\rm Glu}}} \). The temperature sensitive elp3Δ strain derivatives were cultivated at permissive (30 °C) or semi-permissive (34 °C) growth conditions.

Results

Culturing an elp3Δ strain at 30 or 34 °C resulted in altered metabolism of 36 and 46 %, respectively, of all metabolites detected when compared to an elp3Δ strain carrying the wild-type ELP3 gene. Overexpression of hypomodified \( {\text {tRNA}_{{\rm s^{2} {\rm UUU}}}^{{\rm Lys}} , {\rm tRNA}_{{\rm s^{2} {\rm UUG}}}^{{\rm Gln }} \;{\rm and}\;{\rm tRNA}_{{\rm s^{2} {\rm UUC}}}^{{\rm Glu}}} \) suppressed a subset of the metabolic alterations observed in the elp3Δ strain.

Conclusion

Our results suggest that the presence of ncm⁵- and mcm⁵-side chains on wobble uridines in tRNA are important for metabolic homeostasis.

     

Retention of Dissolved Inorganic Nitrogen by Foliage and Twigs of Four Temperate Tree Species

Nitrogen (N) retention by tree canopies is believed to be an important process for tree nutrient uptake, and its quantification is a key issue in determining the impact of atmospheric N deposition on forest ecosystems. Due to dry deposition and retention by other canopy elements, the actual uptake and assimilation by the tree canopy is often obscured in throughfall studies. In this study, ¹⁵N-labeled solutions ( $ ^{15} {\text{NH}}_{4}^{ + } $ and $ ^{15} {\text{NO}}_{3}^{ - } $ ) were used to assess dissolved inorganic N retention by leaves/needles and twigs of European beech, pedunculate oak, silver birch, and Scots pine saplings. The effects of N form, tree species, leaf phenology, and applied $ {\text{NO}}_{3}^{ - } $ to $ {\text{NH}}_{4}^{ + } $ ratio on the N retention were assessed. Retention patterns were mainly determined by foliar uptake, except for Scots pine. In twigs, a small but significant ¹⁵N enrichment was detected for $ {\text{NH}}_{4}^{ + } $ , which was found to be mainly due to physicochemical adsorption to the woody plant surface. The mean $ {{^{15} {\text{NH}}_{4}^{ + } } \mathord{\left/ {\vphantom {{^{15} {\text{NH}}_{4}^{ + } } {^{15} {\text{NO}}_{3}^{ - } }}} \right. \kern-0em} {^{15} {\text{NO}}_{3}^{ - } }} $ retention ratio varied considerably among species and phenological stadia, which indicates that the use of a fixed ratio in the canopy budget model could lead to an over- or underestimation of the total N retention. In addition, throughfall water under each branch was collected and analyzed for $ ^{15} {\text{NH}}_{4}^{ + } $ , $ ^{15} {\text{NO}}_{3}^{ - } $ , and all major ions. Net throughfall of $ ^{15} {\text{NH}}_{4}^{ + } $ was, on average, 20 times higher than the actual retention of $ ^{15} {\text{NH}}_{4}^{ + } $ by the plant material. This difference in $ ^{15} {\text{NH}}_{4}^{ + } $ retention could not be attributed to pools and fluxes measured in this study. The retention of $ ^{15} {\text{NH}}_{4}^{ + } $ was correlated with the net throughfall of K⁺, Mg²⁺, Ca²⁺, and weak acids during leaf development and the fully leafed period, while no significant relationships were found for $ ^{15} {\text{NO}}_{3}^{ - } $ retention. This suggests that the main driving factors for $ {\text{NH}}_{4}^{ + } $ retention might be ion exchange processes during the start and middle of the growing season and passive diffusion at leaf senescence. Actual assimilation or abiotic uptake of N through leaves and twigs was small in this study, for example, 1–5% of the applied dissolved ¹⁵N, indicating that the impact of canopy N retention from wet deposition on forest productivity and carbon sequestration is likely limited.     

ARTIFICIAL SELECTION FOR PAEDOMORPHOSIS IN THE SALAMANDER AMBYSTOMA TALPOIDEUM

Heterochronic ontogenetic mechanisms such as paedomorphosis are potentially important mechanisms of both microevolutionary and macroevolutionary change. The salamander Ambystoma talpoideum is facultatively paedomorphic. Expression of paedomorphosis in this species varies among local natural populations. Two breeding lines, one from a population associated with a temporary pond where metamorphosis to a terrestrial adult always occurs, another from a population associated with a nearly permanent pond where paedomorphosis is common, were selected artificially for paedomorphosis over four generations. The F₅ generation of each breeding line was reared in a “common garden” field experiment under two drying regimes to simulate the larval environment in a temporary and in a permanent pond. There was a significantly different response to the drying regimes and to the artificial selection in the two lines. A significant population × selection interaction indicated that the two populations responded differently to artificial selection for paedomorphosis. The presence of heritable genetic variation suggests that evolution and divergence among populations of salamanders is possible with intense natural selection over short periods of ecological time.     

A comparative study of the mechanism of Na+ and Cl? excretion by the gill ofMugil capito andFundulus heteroclitus: Effects of Stress

Summary In seawater (SW)-adaptedMugil andFundulus, gill effluxes of Na⁺ and of Cl^– and the simultaneously recorded transgill potential (P.D.) differ according to whether they are measured in stressed or rested animals.In rested animals of the two species, transfer to Ringer's solution considerably reduces the P.D. but not . InFundulus, is also decreased. Transfer of the two species from SW to fresh water (FW) reduces and by 75 to 85% and leads to a large inversion of P.D. When K⁺ is added to FW, a gill depolarization occurs, as well as a large increase of and .These results suggest that: 1) the P.D. originates primarily from the diffusion of cations, the gill permeability to Na⁺ ( ) being greater than that to Cl^– ( ), 2) a Cl^–/Cl^– exchange independent of P.D. is associated with the Cl^– pump; 3) Cl^– pump activity is linked to Na⁺/K⁺ exchange which in turn is associated to a Na⁺/Na⁺ exchange diffusion mechanism.In stressed individuals of the two species, the P.D. in SW, as well as the P.D. changes observed during transfer experiments, are considerably reduced. The decrease of and observed after transfer from SW to FW are also minimised. Changes are smaller inFundulus. The decrease of P.D. characterizing stressed animals may be at least in part due to a 3 to 4 fold increase of which becomes equal to in both species.As a result of stress, the K⁺-activated Na⁺ and Cl^– excretion mechanisms are totally inhibited inFundulus and partially so inMugil.Stress response seems more intense inFundulus and recovery from stress faster inMugil.     

Energetics of the growth of Methanobacterium thermoautotrophicum and Methanococcus thermolithotrophicus on ammonium chloride and dinitrogen

Methanobacterium thermoautotrophicum was grown in continuous culture in a fermenter gassed with H₂ and CO₂ as sole carbon and energy sources, and in a medium which contained either NH₄Cl or gaseous N₂ as nitrogen source. Growth was possible with N₂. Steady states were obtained at various gas flow rates with NH₄Cl and with and the maintenance coefficient varied with the gas input and with the nitrogen source. Growth of Methanococcus thermolithotrophicus in continuous culture in a fermenter gassed with H₂, CO₂ as nitrogen, carbon and energy sources was also examined.Abbreviations molecular growth yield (g dry weight of cells per mol of CH₄ evolved) - growth rate (h^-1) - D dilution rate (h^-1) - rate (h_-1); relation of Neijssel and Tempest and of Stouthamer and Bettenhaussen - energy     

3D-QSAR studies of triazolopyrimidine derivatives of <Emphasis Type="Italic">Plasmodium falciparum</Emphasis> dihydroorotate dehydrogenase inhibitors using a combination of molecular dynamics,docking, and genetic algorithm-based methods

A series of 35 triazolopyrimidine analogues reported as Plasmodium falciparum dihydroorotate dehydrogenase (PfDHODH) inhibitors were optimized using quantum mechanics methods, and their binding conformations were studied by docking and 3D quantitative structure–activity relationship studies. Genetic algorithm-based criteria was adopted for selection of training and test sets while maintaining structural diversity of training and test sets, which is also very crucial for model development and validation. Both the comparative molecular field analyses ( q_\textLOO² = 0.841 q_{\text{LOO}}^2 = 0.{841} , r_\textncv² = 0.99 r_{\text{ncv}}^2 = 0.{99} ) and comparative molecular similarity indices analyses ( q_\textLOO² = 0.757 q_{\text{LOO}}^2 = 0.{757} , r_\textncv² = 0.943 r_{\text{ncv}}^2 = 0.{943} ) show excellent correlation and high predictive power. Furthermore, molecular dynamics simulations were performed to explore the binding mode of the two of the most active compounds of the series, 10 and 14. Harmonization in the two simulation results validate the analysis and therefore applicability of docking parameters based on crystallographic conformation of compound 14 bound to receptor molecule. This work provides useful information about the inhibition mechanism of this class of molecules and will assist in the design of more potent inhibitors of PfDHODH.     

Effects of common soil anions and pH on the uptake and accumulation of perchlorate in lettuce

A mechanistic understanding of perchlorate () entry into plants is important for establishing the human health risk associated with consumption of contaminated produce and for assessing the effectiveness of phytoremediation. To determine whether common soil anions affect uptake and accumulation in higher plants, a series of competition experiments using lettuce (Lactuca sativa L.) were conducted between (50 nM) and (4–12 mM), (1–10 mM), or Cl⁻ (5–15 mM) in hydroponic solution. The effects of (0–5 mM) and pH (5.5–7.5) on uptake were also examined. Increasing in solution significantly reduced the amount of taken up by green leaf, butter head, and crisphead lettuces. Sulfate and Cl⁻ had no significant effects on uptake in lettuce over the concentrations tested. Increasing pH significantly reduced the amount of taken up by crisphead and green leaf lettuces, whereas increasing significantly reduced uptake in butter head lettuce. The inhibition by across all lettuce genotypes suggests that may share an ion carrier with , and the decrease in uptake with increasing pH or provides macroscopic evidence for cotransport across the plasma membrane.     

Novel approach to heritability detection suggests robustness to paternal genotype in a complex morphological trait

Heritable variation is essential for evolution by natural selection. In Neotropical army ants, the ecological role of a given species is linked intimately to the morphological variation within the sterile worker caste. Furthermore, the army ant Eciton burchellii is highly polyandrous, presenting a unique opportunity to explore heritability of morphological traits among related workers sharing the same colonial environment. In order to exploit the features of this organismal system, we generated a large genetic and morphological dataset and applied our new method that employs geometric morphometrics (GM) to detect the heritability of complex morphological traits. After validating our approach with an existing dataset of known heritability, we simulated our ability to detect heritable variation given our sampled genotypes, demonstrating the method can robustly recover heritable variation of small effect size. Using this method, we tested for genetic caste determination and heritable morphological variation using genetic and morphological data on 216 individuals of E. burchellii. Results reveal this ant lineage (1) has the highest mating frequency known in ants, (2) demonstrates no paternal genetic caste determination, and (3) suggests a lack of heritable morphological variation in this complex trait associated with paternal genotype. We recommend this method for leveraging the increased resolution of GM data to explore and understand heritable morphological variation in nonmodel organisms.     

Effective size of an Atlantic salmon (Salmo salar L.) metapopulation in Northern Spain

The genetic diversity of metapopulations is influenced not only by the effective sizes (N _e ) of individual subpopulations, but also by the total effective size of the metapopulation (meta-N _e ). We estimated meta-N _e of four neighbouring Atlantic salmon populations connected by gene flow using genetic estimates of subpopulation N _e s and migration rates derived from capture–recapture data. The meta-[^(N)]_e meta{\hbox{-}}\hat{N}_{e} was lower than the sum of [^(N)]_e \hat{N}_{e} s of the subpopulations, suggesting that genetic diversity harboured by the four river salmon metapopulation is lower than what would have been expected by viewing individual subpopulations separately. In addition, meta-[^(N)]_e meta{\hbox{-}}\hat{N}_{e} was found to be sensitive to changes in [^(N)]_e \hat{N}_{e} of the subpopulation from which net emigration rate was largest, so as that the genetic diversity of the metapopulation would be best preserved by avoiding any reductions in N _e of this subpopulation. Yet, this subpopulation is the one that has historically—and still is—experiencing the highest exploitation rate in the metapopulation system.     

Transition from octahedral to tetrahedral geometry causes the activation or inhibition by Zn<Superscript>2+</Superscript> of <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> phosphorylcholine phosphatase

Pseudomonas aeruginosa phosphorylcholine phosphatase (PchP) catalyzes the hydrolysis of phosphorylcholine, which is produced by the action of hemolytic phospholipase C on phosphatidylcholine or sphyngomielin, to generate choline and inorganic phosphate. Among divalent cations, its activity is dependent on Mg²⁺ or Zn²⁺. Mg²⁺ produced identical activation at pH 5.0 and 7.4, but Zn²⁺ was an activator at pH 5.0 and became an inhibitor at pH 7.4. At this higher pH, very low concentrations of Zn²⁺ inhibited enzymatic activity even in the presence of saturating Mg²⁺ concentrations. Considering experimental and theoretical physicochemical calculations performed by different authors, we conclude that at pH 5.0, Mg²⁺ and Zn²⁺ are hexacoordinated in an octahedral arrangement in the PchP active site. At pH 7.4, Mg²⁺ conserves the octahedral coordination maintaining enzymatic activity. The inhibition produced by Zn²⁺ at 7.4 is interpreted as a change from octahedral to tetrahedral coordination geometry which is produced by hydrolysis of the [ \textZn ²⁺ \textL ₂ ^{- 1} \textL ₂⁰ ( \textH ₂ \textO ) ₂ ] \left[ {{\text{Zn}}^{ 2+ } {\text{L}}_{ 2}^{ - 1} {\text{L}}_{ 2}^{0} \left( {{\text{H}}_{ 2} {\text{O}}} \right)_{ 2} } \right] complex.