Mapping reciprocal effects and interactions with plant density stress in Zea mays L

Reciprocal effects are due to genetic effects of the parents (i.e. maternal and paternal effects), cytoplasmic effects and parent-of-origin effects. However, in Zea mays L. the extent to which reciprocal effects exist, or can be attributed to specific underlying components, remains an area of interest and study. Reciprocal effects have been reported by several investigators for various agronomic characters in different types of maize materials for grain and silage usage. Maize geneticists and breeders have recognized reciprocal effects as one source of genetic variability, but the lack of consistency in the observation of these effects, particularly due to stress conditions, has prevented a systematic exploitation of these effects in practical breeding programs. There is mounting molecular evidence for underlying mechanisms in maize, which could be responsible for both the existence, and the instability of reciprocal effects. In this study, we developed population of reciprocal backcrosses based on an initial set of recombinant inbred lines. This population was used for dissecting reciprocal effects into the underlying components (maternal, cytoplasmic and parent-of-origin) effects. We also developed statistical framework to identify and map contributions of specific nuclear chromosomal regions to reciprocal effects. We showed that differences in maternal parents, endosperm DNA and maternally transmitted factors collectively influence reciprocal effects early during the season, and that their influence diluted at later stages. We also found evidence that parent-of-origin effects in the sporophyte DNA existed at all stages and played an important role in establishing differences between reciprocal backcrosses at later developmental stages.     

When to rely on maternal effects and when on phenotypic plasticity?

Existing insight suggests that maternal effects have a substantial impact on evolution, yet these predictions assume that maternal effects themselves are evolutionarily constant. Hence, it is poorly understood how natural selection shapes maternal effects in different ecological circumstances. To overcome this, the current study derives an evolutionary model of maternal effects in a quantitative genetics context. In constant environments, we show that maternal effects evolve to slight negative values that result in a reduction of the phenotypic variance (canalization). By contrast, in populations experiencing abrupt change, maternal effects transiently evolve to positive values for many generations, facilitating the transmission of beneficial maternal phenotypes to offspring. In periodically fluctuating environments, maternal effects evolve according to the autocorrelation between maternal and offspring environments, favoring positive maternal effects when change is slow, and negative maternal effects when change is rapid. Generally, the strongest maternal effects occur for traits that experience very strong selection and for which plasticity is severely constrained. By contrast, for traits experiencing weak selection, phenotypic plasticity enhances the evolutionary scope of maternal effects, although maternal effects attain much smaller values throughout. As weak selection is common, finding substantial maternal influences on offspring phenotypes may be more challenging than anticipated.     

Analysis of genetic effects on nutrient quality traits in indica rice

Nine cytoplasmic male-sterile lines and five restorer lines were used in an incomplete diallel cross to analyze seed effects, cytoplasmic effects, and maternal gene effects on nutrient quality traits of indica rice (Oryza sauva L.). The results indicated that nutrient quality traits were controlled by cytoplasmic and maternal effects as well as by seed direct effects. Maternal effects for lysine content (LC), lysine index (LI), and the ratio of lysine content to protein content (RLP) were more important than seed direct effects, while protein content (PC) and protein index (PI) were mainly affected by seed direct effects. Cytoplasmic effects accounted for 2.41–20.80% of the total genetic variation and were significant for all nutrient quality traits. Additive genetic effects were much more important than dominance effects for all of the traits studied, so that selection could be applied for these traits in early generations.     

Pièges et artéfacts en imagerie TEP/TDM : intérêts des post-traitements

In PET imaging, quantification of the acquired data can be achieved by using a series of correction techniques to minimize the effects inherent in the imaging process of emission tomography. Quantitative images can be reconstructed after correcting the detected emission data for the presence of random and scattered coincidences, attenuation effects, effects associated with the variable detectors sensitivity, effects related to the geometry of the device and the effects of dead-time. All these effects are well accounted for in the PET imaging market. However, other effects can degrade the quality of the PET images, such as the finite spatial resolution generating partial volume effects, or the patient movements including respiratory and cardiac physiological movements. In the thoracic field, the effects of respiratory motion on PET images are characterized by a loss of detection sensitivity due to the associated blur. Several methods have been developed to correct for these effects, but still without a wide acceptance in clinical routine. These research areas are therefore still very active.     

Concentration Addition,Independent Action and Generalized Concentration Addition Models for Mixture Effect Prediction of Sex Hormone Synthesis In Vitro

Humans are concomitantly exposed to numerous chemicals. An infinite number of combinations and doses thereof can be imagined. For toxicological risk assessment the mathematical prediction of mixture effects, using knowledge on single chemicals, is therefore desirable. We investigated pros and cons of the concentration addition (CA), independent action (IA) and generalized concentration addition (GCA) models. First we measured effects of single chemicals and mixtures thereof on steroid synthesis in H295R cells. Then single chemical data were applied to the models; predictions of mixture effects were calculated and compared to the experimental mixture data. Mixture 1 contained environmental chemicals adjusted in ratio according to human exposure levels. Mixture 2 was a potency adjusted mixture containing five pesticides. Prediction of testosterone effects coincided with the experimental Mixture 1 data. In contrast, antagonism was observed for effects of Mixture 2 on this hormone. The mixtures contained chemicals exerting only limited maximal effects. This hampered prediction by the CA and IA models, whereas the GCA model could be used to predict a full dose response curve. Regarding effects on progesterone and estradiol, some chemicals were having stimulatory effects whereas others had inhibitory effects. The three models were not applicable in this situation and no predictions could be performed. Finally, the expected contributions of single chemicals to the mixture effects were calculated. Prochloraz was the predominant but not sole driver of the mixtures, suggesting that one chemical alone was not responsible for the mixture effects. In conclusion, the GCA model seemed to be superior to the CA and IA models for the prediction of testosterone effects. A situation with chemicals exerting opposing effects, for which the models could not be applied, was identified. In addition, the data indicate that in non-potency adjusted mixtures the effects cannot always be accounted for by single chemicals.     

橙腹田鼠中延缓性密度依赖效应和种群波动

检验了延迟的密度依赖对橙腹田鼠 (Microtusochrogaster)一个波动种群的生存和生殖的影响 ,研究持续了 63个月 ,取样间隔为 3 5天。在研究期间 ,该种群的密度经历了 4次波动 ,每次波动的高峰都在 11月至次年 1月 ,种群数量在冬季下降。生存和生殖都有负面的密度依赖效应 ,最大效应具有 2个月的时滞。种群存活率增长对种群密度最大的正面效应具有 2个月的时滞 ,而对与增加生殖则有 3个月的时滞。内部因素和冬季都可能推延对生殖的密度依赖效应 ,但是本文未能检验这些内部因素的影响。季节性影响看来与对生存的延缓性密度依赖效应无关。负面的延缓性密度依赖效应对生存和生殖的净作用可能在于减少、而不是阻止橙腹田鼠种群波动的幅度     

烤烟主要农艺性状的遗传与相关分析

利用包括基因型与环境互作的加性-显性遗传模型,对14个烤烟品种(系)及其配制的41个杂交组合在4个环境下的7个农艺性状表现进行遗传分析。结果表明,株高、节距、腰叶宽主要受加性效应控制,叶数、腰叶长受显性×环境互作效应影响最大,茎围以加性×环境互作效应、显性×环境互作效应为主,产量以加性效应、显性×环境互作效应为主。适应当地生态条件的品种（系）具有较高的正向加性效应。许多组合的显性主效应及在各试验点的显性×环境互作效应在方向上不尽一致,杂交组合的选配宜针对特定的生态环境进行。性状相关分析表明,大多数成对性状的各项相关系数为正值,且多以加性遗传相关为主,可利用株高对产量进行间接选择。
     

RELATIVE CONTRIBUTION OF ADDITIVE, DOMINANCE, AND IMPRINTING EFFECTS TO PHENOTYPIC VARIATION IN BODY SIZE AND GROWTH BETWEEN DIVERGENT SELECTION LINES OF MICE

Epigenetic effects attributed to genomic imprinting are increasingly recognized as an important source of variation in quantitative traits. However, little is known about their relative contribution to phenotypic variation compared to those of additive and dominance effects, and almost nothing about their role in phenotypic evolution. Here we address these questions by investigating the relative contribution of additive, dominance, and imprinting effects of quantitative trait loci (QTL) to variation in "early" and "late" body weight in an intercross of mice selected for divergent adult body weight. We identified 18 loci on 13 chromosomes; additive effects accounted for most of the phenotypic variation throughout development, and imprinting effects were always small. Genetic effects on early weight showed more dominance, less additive, and, surprisingly, less imprinting variation than that of late weight. The predominance of additivity of QTL effects on body weight follows the expectation that additive effects account for the evolutionary divergence between selection lines. We hypothesize that the appearance of more imprinting effects on late body weight may be a consequence of divergent selection on adult body weight, which may have indirectly selected for alleles showing partial imprinting effects due to their associated additive effects, highlighting a potential role of genomic imprinting in the response to selection.     

Lower-order effects adjustment in quantitative traits model-based multifactor dimensionality reduction

Identifying gene-gene interactions or gene-environment interactions in studies of human complex diseases remains a big challenge in genetic epidemiology. An additional challenge, often forgotten, is to account for important lower-order genetic effects. These may hamper the identification of genuine epistasis. If lower-order genetic effects contribute to the genetic variance of a trait, identified statistical interactions may simply be due to a signal boost of these effects. In this study, we restrict attention to quantitative traits and bi-allelic SNPs as genetic markers. Moreover, our interaction study focuses on 2-way SNP-SNP interactions. Via simulations, we assess the performance of different corrective measures for lower-order genetic effects in Model-Based Multifactor Dimensionality Reduction epistasis detection, using additive and co-dominant coding schemes. Performance is evaluated in terms of power and familywise error rate. Our simulations indicate that empirical power estimates are reduced with correction of lower-order effects, likewise familywise error rates. Easy-to-use automatic SNP selection procedures, SNP selection based on "top" findings, or SNP selection based on p-value criterion for interesting main effects result in reduced power but also almost zero false positive rates. Always accounting for main effects in the SNP-SNP pair under investigation during Model-Based Multifactor Dimensionality Reduction analysis adequately controls false positive epistasis findings. This is particularly true when adopting a co-dominant corrective coding scheme. In conclusion, automatic search procedures to identify lower-order effects to correct for during epistasis screening should be avoided. The same is true for procedures that adjust for lower-order effects prior to Model-Based Multifactor Dimensionality Reduction and involve using residuals as the new trait. We advocate using "on-the-fly" lower-order effects adjusting when screening for SNP-SNP interactions using Model-Based Multifactor Dimensionality Reduction analysis.     

Direct, maternal, and sibsocial genetic effects on individual and colony traits in an ant

When social interactions occur, the phenotype of an individual is influenced directly by its own genes (direct genetic effects) but also indirectly by genes expressed in social partners (indirect genetic effects). Social insect colonies are characterized by extensive behavioral interactions among workers, brood, and queens so that indirect genetic effects are particularly relevant. I used a series of experimental manipulations to disentangle the contribution of direct effects, maternal (queen) effects, and sibsocial (worker) effects to variation for worker, gyne, and male mass; caste ratio; and sex ratio in the ant Temnothorax curvispinosus. The results indicate genetic variance for direct, maternal, and sibsocial effects for all traits, except for male mass there was no significant maternal variance, and for sex ratio the variance for direct effects was not separable from maternal variance for the primary sex ratio. Estimates of genetic correlations between direct, maternal, and sibsocial effects were generally negative, indicating that these effects may not evolve independently. These results have broad implications for social insect evolution. For example, the genetic architecture underlying social insect traits may constrain the realization of evolutionary conflicts between social partners.     

Effects of residual smoothing on the posterior of the fixed effects in disease-mapping models

Disease-mapping models for areal data often have fixed effects to measure the effect of spatially varying covariates and random effects with a conditionally autoregressive (CAR) prior to account for spatial clustering. In such spatial regressions, the objective may be to estimate the fixed effects while accounting for the spatial correlation. But adding the CAR random effects can cause large changes in the posterior mean and variance of fixed effects compared to the nonspatial regression model. This article explores the impact of adding spatial random effects on fixed effect estimates and posterior variance. Diagnostics are proposed to measure posterior variance inflation from collinearity between the fixed effect covariates and the CAR random effects and to measure each region's influence on the change in the fixed effect's estimates by adding the CAR random effects. A new model that alleviates the collinearity between the fixed effect covariates and the CAR random effects is developed and extensions of these methods to point-referenced data models are discussed.     

Rapid and estrogen receptor beta mediated actions in the hippocampus mediate some functional effects of estrogen

The steroid hormone, estradiol (E(2)), has numerous targets in the central nervous system, including the hippocampus, which plays a key role in cognition and affective behavior. This review focuses on our evidence from studies in rodents that E(2) has diverse mechanisms in the hippocampus for its functional effects. E(2) has rapid, membrane-mediated effects in the hippocampus to enhance cognitive performance. Administration of E(2) to the hippocampus of rats for 10 min following training enhances performance in a hippocampus-mediated task. Increased cell firing in the hippocampus occurs within this short-time frame. Furthermore, administration of free E(2) or an E(2) conjugate, E(2):bovine serum albumin (BSA), to the hippocampus produces similar performance-enhancing effects in this task, suggesting that E(2) has membrane actions in the hippocampus for these effects. Further evidence that E(2) has rapid, membrane-mediated effects is that co-administration of E(2) and inhibitors of mitogen-activated protein kinase (MAPK), rather than intracellular E(2) receptors (ERs) or protein synthesis, attenuate the enhancing effects of E(2) in this task. Despite these data that demonstrate E(2) can have rapid and/or membrane-mediated effects in the hippocampus, there is clear evidence to suggest that intracellular ERs, particularly the beta (rather than alpha) isoform of ERs, may be important targets for E(2)'s functional effects for hippocampal processes. Administration of ligands that are specific for ERbeta, but not ERalpha, have enhancing effects on hippocampal processes similar to that of E(2) (which has similar affinity for ERalpha and ERbeta). These effects are attenuated when ERbeta expression is knocked down in transgenic models or with central administration of antisense oligonucleotides. Thus, there may be a convergence of E(2)'s actions through rapid, membrane-mediated effects and intracellular ERs in the hippocampus for these functional effects.     

Anticonvulsant drugs for management of pain: a systematic review.

OBJECTIVE--To determine effectiveness and adverse effects of anticonvulsant drugs in management of pain. DESIGN--Systematic review of randomised controlled trials of anticonvulsants for acute, chronic, or cancer pain identified by using Medline, by hand searching, by searching reference lists, and by contacting investigators. SUBJECTS--Between 1966 and February 1994, 37 reports were found; 20 reports, of four anticonvulsants, were eligible. MAIN OUTCOME MEASURES--Numbers needed to treat were calculated for effectiveness, adverse effects, and drug related withdrawal from study. RESULTS--The only placebo controlled study in acute pain found no analgesic effect of sodium valproate. For treating trigeminal neuralgia, carbamazepine had a combined number needed to treat of 2.6 for effectiveness, 3.4 for adverse effects, and 24 for severe effects (withdrawal from study). For treating diabetic neuropathy, anticonvulsants had a combined number needed to treat of 2.5 for effectiveness, 3.1 for adverse effects, and 20 for severe effects. For migraine prophylaxis, anticonvulsants had a combined number needed to treat of 1.6 for effectiveness, 2.4 for adverse effects, and 39 for severe effects. Phenytoin had no effect on the irritable bowel syndrome, and carbamazepine had little effect on pain after stroke. Clonazepam was effective in one study for temporomandibular joint dysfunction. No study compared one anticonvulsant with another. CONCLUSIONS--Anticonvulsants were effective for trigeminal neuralgia and diabetic neuropathy and for migraine prophylaxis. Minor adverse effects occurred as often as benefit.     

Social effects of territorial neighbours on the timing of spring breeding in North American red squirrels

Organisms can affect one another's phenotypes when they socially interact. Indirect genetic effects occur when an individual's phenotype is affected by genes expressed in another individual. These heritable effects can enhance or reduce adaptive potential, thereby accelerating or reversing evolutionary change. Quantifying these social effects is therefore crucial for our understanding of evolution, yet estimates of indirect genetic effects in wild animals are limited to dyadic interactions. We estimated indirect phenotypic and genetic effects, and their covariance with direct effects, for the date of spring breeding in North American red squirrels (Tamiasciurus hudsonicus) living in an array of territories of varying spatial proximity. Additionally, we estimated indirect effects and the strength of selection at low and high population densities. Social effects of neighbours on the date of spring breeding were different from zero at high population densities but not at low population densities. Indirect phenotypic effects accounted for a larger amount of variation in the date of breeding than differences attributable to the among‐individual variance, suggesting social interactions are important for determining breeding dates. The genetic component to these indirect effects was however not statistically significant. We therefore showcase a powerful and flexible method that will allow researchers working in organisms with a range of social systems to estimate indirect phenotypic and genetic effects, and demonstrate the degree to which social interactions can influence phenotypes, even in a solitary species.     

IV. Discriminative stimulus effects of narcotics: Evidence for multiple receptor-mediated actions

Results of studies on the discriminative stimulus effects of narcotics are consistent with the hypothesis that multiple receptors mediate the effects of these compounds. In the rat, at least three subsets of discriminative effects exist, although some drugs appear to have effects that transcend more than one subset. The discriminative effects of morphine-like narcotics (μ agonists), for example, are often clearly distinguishable from the discriminative effects produced by κ agonists, such as ketazocine, and from those produced by phencyclidine-like agonists, such as SKF-10,047 and cyclazocine. Cyclazocine, however, has been reported to have discriminative effects in common with morphine (45) and fentanyl (17) and appears to have κ-like, in addition to phencyclidine-like, discriminative effects. The relative ability of pure narcotic antagonists to block the discriminative effects of these compounds also provides evidence for distinct pharmacologic actions of these drugs. In the rat, the discriminative effects of morphine are blocked by doses of naloxone that are considerably smaller than those that are needed to block the discriminative effects of cyclazocine (44). The discriminative effects of phencyclidine are not altered at all by naltrexone (63).     

The evidence for Allee effects

Allee effects are an important dynamic phenomenon believed to be manifested in several population processes, notably extinction and invasion. Though widely cited in these contexts, the evidence for their strength and prevalence has not been critically evaluated. We review results from 91 studies on Allee effects in natural animal populations. We focus on empirical signatures that are used or might be used to detect Allee effects, the types of data in which Allee effects are evident, the empirical support for the occurrence of critical densities in natural populations, and differences among taxa both in the presence of Allee effects and primary causal mechanisms. We find that conclusive examples are known from Mollusca, Arthropoda, and Chordata, including three classes of vertebrates, and are most commonly documented to result from mate limitation in invertebrates and from predator–prey interactions in vertebrates. More than half of studies failed to distinguish component and demographic Allee effects in data, although the distinction is crucial to most of the population-level dynamic implications associated with Allee effects (e.g., the existence of an unstable critical density associated with strong Allee effects). Thus, although we find conclusive evidence for Allee effects due to a variety of mechanisms in natural populations of 59 animal species, we also find that existing data addressing the strength and commonness of Allee effects across species and populations is limited; evidence for a critical density for most populations is lacking. We suggest that current studies, mainly observational in nature, should be supplemented by population-scale experiments and approaches connecting component and demographic effects. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Developmental behavior of gene expression for brown rice thickness under different environments

The dynamic changes of genetic effects, including main effects, and genotype x environment (GE) interaction effects on brown rice thickness (BRT) across environments were investigated by using the developmental genetic models. Seven cytoplasmic male sterile lines of indica rice (Oryza sativa L.) as females and five restoring lines as males were used in a factorial design to produce grains of F(1)s and F(2)s in two environments (years) for developmental genetic analysis. The results indicate that genetic effects, especially GE interaction effects of triploid endosperm genes, cytoplasm genes, and diploid maternal plant genes were important to the performance of BRT at various filling stages of rice. The BRT was genetically controlled by the net genetic effects of genes expressed at the early and late filling stages (1-7 days and 15-21 days after flowering, respectively). The differences in net genetic effects under different environments for endosperm, cytoplasm, and maternal plant genes were found, and the net GE interaction effects were more important to BRT at the early filling and mature stages of rice. Some net genetic effects, especially for net cytoplasm effects spasmodically expressed, were detected among filling stages. Higher additive and cytoplasm main effects, along with their interaction effects, were found, which would be useful for selection for BRT in breeding programs. The predicated genetic effects at different filling stages show that the parents of V20 and Xieqingzao were better than others for improving BRT of progenies.     

Partitioning the variation in mammalian substitution rates

We have used analysis of variance to partition the variation in synonymous and amino acid substitution rates between three effects (gene, lineage, and a gene-by-lineage interaction) in mammalian nuclear and mitochondrial genes. We find that gene effects are stronger for amino acid substitution rates than for synonymous substitution rates and that lineage effects are stronger for synonymous substitution rates than for amino acid substitution rates. Gene-by-lineage interactions, equivalent to overdispersion corrected for lineage effects, are found in amino acid substitutions but not in synonymous substitutions. The variance in the ratio of amino acid and synonymous substitution rates is dominated by gene effects, but there is also a significant gene-by-lineage interaction.     

Use of genetic effects and genotype by environmental interactions for the classification of mexican races of maize

To examine the questions of whether the additive and dominance effects present for morphological characters in racial crosses are of sufficient consistency and magnitude to allow such genetic effects to be used for racial classification, we used a diallel experiment among the 25 well-defined Mexican races of maize, which include the ancestral stocks of most commercial and genetic maize types. With such an experiment, genetic effects and genotype by environmental interactions for one or more characters can be used to measure genetic and adaptational or environmental similarity. We used average parental effects (general combining abilities), specific effects, and genotype by environmental effects of 21 characters from the diallel (grown at three locations) to group the Mexican races of maize. The groupings based upon average genetic effects and upon genotype by environmental interactions are more satisfactory than groupings based upon specific effects. The standard errors for genetic distances based upon specific (largely dominance) effects seem to be too high for practical use. Principal components analyses of the same data suggest a similar conclusion.-The groupings based upon average genetic effects are in general agreement with previous studies, with the exception of Maíz Dulce, which is grouped with the Cónicos, rather than being isolated from the other Mexican races of maize.     

Performance of crosses among flint maize populations under infestation by Sesamia nonagrioides (Lepidoptera: Noctuidae)

Flint maize, Zea mays L., varieties provide some interesting agronomic characteristics and kernels that possess a better ability than other kernels for developing high-quality flour. The pink stem borer, Sesamia nonagrioides Lefebvre, is an important constraint for the maize crop in Mediterranean regions. The objective of this work was to identify a "flint x flint" heterotic pattern that would perform well under artificial infestation by S. nonagrioides. A 10-population diallel was evaluated under infestation by S. nonagrioides in 2 yr. Variety effects were the only significant effects involved in stem and ear resistance to S. nonagrioides attack. Variety effects and average heterosis effects were the only significant effects for grain yield under artificial infestation conditions. Considering variety effects and cross-performance, the heterotic pattern Basto/Enano levantixo x Longfellow (BA/EL x LO) would be recommended for obtaining flint maize hybrids tolerant to S. nonagrioides attack because BA/EL had the most favorable variety effects for stem resistance, LO exhibited the most positive variety effects for grain yield, and the cross BA/EL x LO yielded significantly more than the remaining crosses.