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Results for “trait plasticity”

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PubMed2005

Relationships among growth, development and plastic response to environment quality in a perennial plant.

Phenotypic traits differ between plants in different environments and within individuals as they grow and develop. Comparing plants in different environments at a common age can obscure the developmental basis for differences in phenotype means in different environments. Here, we compared trait means and patterns of trait ontogeny for perennial (Viola septemloba) plants growing in environments that differed in quality either naturally or due to experimental manipulation. Consistent with predictions for adaptive stress resistance, plants grown in lower-quality environments allocated proportionately more biomass to roots and rhizomes, and produced smaller, thicker and longer-lived leaves. The developmental trajectory of almost all traits differed between environments, and these differences contributed to observed differences in trait means. Plants were able to alter their initial developmental trajectory in response to an increase in resources after 8 wk of growth. This result contrasts with previous findings, and may reflect a difference in the way that annual and perennial species respond to stress. Our results demonstrate the complexity of interactions between the environment and the development of the phenotype that underlie putatively adaptive plastic responses to environment quality.

Adaptation, Physiological↗

PubMedDate not supplied

The stem state: plasticity is essential, whereas self-renewal and hierarchy are optional.

The prevailing stem cell concept is derived from the large body of evidence available on the structure of the blood-generating system. Hemopoiesis is organized such that a multipotent stem cell, endowed with self-renewal capacity, is viewed as being positioned at the origin of a hierarchical tree of branching specificities, increasing maturity and decreasing self-renewal ability. Data accumulated in recent years on various stem cell systems often contradict this traditional view of stem cells and are reviewed herein. It is suggested that other options should be considered and put to experimental scrutiny; it is argued that the organization of the hemopoietic system may not represent a general structure of stem cell systems. The basic trait of the stem state is proposed to be plasticity. Self-renewal is not a specific stem cell trait; rather, it is exhibited by some mature cell types, whereas other particular stem cells are endowed with relatively poor renewal ability. Hierarchical structuring is also proposed to be an optional stem cell trait and may exist only in specific tissues where it serves the need for rapid expansion. The stem state is therefore defined by the highest degree of plasticity of a cell, within the repertoire of cell types present in the organism.

Animals↗

PubMed2000

The evolution of compensation to herbivory in scarlet gilia, Ipomopsis aggregata: herbivore-imposed natural selection and the quantitative genetics of tolerance.

Tolerance is the ability of plants to maintain fitness after experiencing herbivore damage. We investigated scarlet gilia tolerance to browsing in the framework of phenotypic plasticity using both an operational and candidate trait approach. Individuals from full-sib families were split into an artificial clipping treatment, a natural-damage treatment, or left as controls. We tested for genetic variation in tolerance by evaluating family x herbivory treatment interactions on fitness in a mixed model analysis of variance. In addition, we used selection analyses to assess the function of flowering phenology and compensatory regrowth (via branch production) as candidate tolerance traits. We found a strong detrimental fitness effect of browsing and considerable variation among sire half-sib families in levels of tolerance (25% to 63% of the fitness of controls). There was no evidence of overcompensation at either the population or family level and no additive genetic variation in operationally defined tolerance. Phenotypic selection analyses provide evidence that early flowering and compensatory regrowth function as tolerance characters. We found strong linear and correlational selection for early flowering and increased branch production for damaged plants and linear selection for apical dominance (reduced branchiness) and early flowering in control plants. Moreover, reduced phenological delay and increased plasticity in branch production were correlated with tolerance. We detected significant additive genetic variation in flowering phenology in both treatments and a positive genetic correlation between the phenology of control and damaged plants. We found significant additive genetic variation in branch production in undamaged and naturally damaged plants, but not in clipped plants. Damaged plants exhibited marginally significant additive genetic variance in fitness, although its heritability was very low (approximately 3.6%). We failed to find additive genetic variation in the fitness of control plants. Our results suggest that tolerance traits are under herbivore-imposed natural selection in this population, but that responses to selection are limited by available genetic variation and selective constraints.

Animals↗

PubMed2006

Cardiovascular system in larval zebrafish responds to developmental hypoxia in a family specific manner.

BACKGROUND: Genetic and environmental variation are both known to influence development. Evolution of a developmental response that is optimized to the environment (adaptive plasticity) requires the existence of genetic variation for that developmental response. In complex traits composed of integrated sets of subsidiary traits, the adaptive process may be slowed by the existence of multiple possible integrated responses. This study tests for family (sibship) specific differences in plastic response to hypoxia in an integrated set of cardiovascular traits in zebrafish. RESULTS: Cardiac output, which is the integrated product of several subsidiary traits, varied highly significantly between families, and families differed significantly in the degree and direction of response to developmental oxygen level. The cardiac output response to oxygen environment was entirely family specific with no significant overall trend due to oxygen level. Constituent physiological variables that contribute to cardiac output all showed significant family specific response to hypoxia. Traits that were not directly related to cardiac output, such as arterial and venous diameter, and red blood cell velocities did not respond to hypoxia in a family specific manner. CONCLUSION: Zebrafish families vary in their plastic response to hypoxia. Genetic variation in plastic response to hypoxia may therefore provide the basic ingredient for adaptation to a variable environment. Considerable variation in the degree of familial response to hypoxia exists between different cardiovascular traits that may contribute to cardiac output. It is possible that the integration of several subsidiary traits into cardiac output allows the maintenance of genetic variance in cardiac response.

Journal Article↗

PubMed2000

Phenotypic plasticity for plant development, function and life history.

A single genotype can produce different phenotypes in different environments. This fundamental property of organisms is known as phenotypic plasticity. Recently, intensive study has shown that plants are plastic for a remarkable array of ecologically important traits, ranging from diverse aspects of morphology and physiology to anatomy, developmental and reproductive timing, breeding system, and offspring developmental patterns. Comparative, quantitative genetics and molecular approaches are leading to new insights into the adaptive nature of plasticity, its underlying mechanisms and its role in the ecological distribution and evolutionary diversification of plants.

Biological Evolution↗

PubMed2005

A comparative analysis of predator-induced plasticity in larval Triturus newts.

Species that occupy similar habitats are expected to show convergent phenotypes. If habitats are defined by the presence of predators, then traits that modify vulnerability to predation, including predator-induced phenotypic plasticity, should be similar within habitats. We tested this idea using larvae of six syntopic newt species belonging to the two Triturus clades. Behavioural plasticity induced by odonate predators was strongly dissimilar between the two main clades but similar within them. Morphological plasticity was variable among species, even between one pair of closely related species. A predation experiment tested whether differences between clades could be caused by differences in body size. Size-specific vulnerability differed between newts in the small-bodied and large-bodied clades, indicating that similar predators may affect the two clades differently. The results showed both similarity and dissimilarity in predator-induced phenotypic plasticity in syntopic larval newts although theory suggests that divergence is unlikely in such ecologically similar species.

Animals↗

PubMed1997

Evolutionary changes of nonlinear reaction norms according to thermal adaptation: a comparison of two Drosophila species.

While the adaptive significance of discontinuous reaction norms is generally accepted, the evolutionary interpretation of continuous response curves remains speculative, and the occurrence of internal constraints is often suggested as an explanation of experimental observations. In Drosophila melanogaster, various morphometrical traits exhibit convex reaction norms to growth temperature, with a maximum value within the developmental thermal range. We compared a cold-adapted species (D. subobscura) with a mid thermal range at 16 degrees C, to the warm-adapted D. melanogaster (mid thermal range at 22 degrees C) for three different morphometrical traits: wing and thorax length in both sexes and ovariole number in females. Maximum value temperatures were ordered in the same way for the three traits in both species: ovariole number > thorax length > wing length. Significant differences were also observed between the two species for the curvature parameter of the quadratic adjustment. The major observation was a significant lateral shift in the reaction norms: maximum values were observed at much lower temperatures in the cold-adapted species than in the warm-adapted one. The parallelism between mid thermal range variation and the position of the maximum value strongly suggests an adaptive displacement of the response curves. Natural selection may thus act not only on trait mean values but also on phenotypic plasticity and on the shape of reaction norms.

Animals↗

PubMed2005

Tumour-cell fusion as a source of myeloid traits in cancer.

Malignant cells express molecular pathways that are also expressed by myeloid cells. Such behaviour is associated with loss of homotypic adhesion between cells, changes in the cellular matrix, induction of angiogenesis, motility, chemotaxis, and several immune-signalling pathways. The overlap between malignant cells and myeloid cells could be explained by one mechanism: fusion of myeloid cells and tumour cells, as noted in animal studies and in two patients with renal-cell carcinoma who underwent bone-marrow transplantation. An overlapping trait in these cells is their glycosylation patterns: hybrids have high expression of N-terminal glycosylation and beta1,6-branched oligosaccharides. In macrophages and cancer cells, these structures have a role in motility and systemic migration; in cancer, they are associated with metastasis and poor prognosis. In addition to myeloid traits, fusion might contribute to aneuploidy and plasticity in cancer. Understanding metastatic cells as myeloid-tumour hybrids suggests new strategies for diagnosis, treatment, and prevention of malignant disease.

Aneuploidy↗

PubMed2004

The 'evolvability' of promiscuous protein functions.

How proteins with new functions (e.g., drug or antibiotic resistance or degradation of man-made chemicals) evolve in a matter of months or years is still unclear. This ability is dependent on the induction of new phenotypic traits by a small number of mutations (plasticity). But mutations often have deleterious effects on functions that are essential for survival. How are these seemingly conflicting demands met at the single-protein level? Results from directed laboratory evolution experiments indicate that the evolution of a new function is driven by mutations that have little effect on the native function but large effects on the promiscuous functions that serve as starting point. Thus, an evolving protein can initially acquire increased fitness for a new function without losing its original function. Gene duplication and the divergence of a completely new protein may then follow.

Aryldialkylphosphatase↗

PubMed1992

Interaction with basement membrane serves to rapidly distinguish growth and differentiation pattern of normal and malignant human breast epithelial cells.

Normal human breast epithelial cells show a high degree of phenotypic plasticity in monolayer culture and express many traits that otherwise characterize tumor cells in vivo. Paradoxically, primary human breast carcinoma cells are difficult to establish in culture: most outgrowths arise from the normal tissue surrounding the tumor. These characteristics have posed major obstacles to the establishment of simple reliable criteria for mammary epithelial transformation in culture. In the present study, we show that a reconstituted basement membrane (BM) can be used to culture all normal human breast epithelial cells and a subset of human breast carcinoma cells. The two cell types can be readily distinguished by virtue of the ability of normal cells to reexpress a structurally and functionally differentiated phenotype within BM. Twelve specimens of normal breast tissue and 2 normal breast epithelial cell lines (total 14 samples) embedded in BM as single cells were able to form multicellular spherical colonies with a final size close to that of true acini in situ. Sections of mature spheres revealed a central lumen surrounded by polarized luminal epithelial cells expressing keratins 18 and 19 and sialomucin at the apical membrane. Significantly, two-thirds of normal spheres deposited a visible endogenous type IV collagen-containing BM even though they were in contact with exogenously provided BM. Growth was arrested completely within the same time period. In contrast, none of 6 carcinoma cell lines or 2 cultures of carcinoma from fresh samples (total 8 samples) responded to BM by growth regulation, lumen formation, correct polarity, or deposition of endogenous BM. These findings may provide the basis of a rapid assay for discriminating normal human breast epithelial cells from their malignant counterparts. Furthermore, we propose that the ability to sense BM appropriately and to form three-dimensional organotypic structures may be the function of a class of "suppressor" genes that are lost as cells become malignant.

Basement Membrane↗

PubMed1999

Social status regulates growth rate: consequences for life-history strategies.

The life-history strategies of organisms are sculpted over evolutionary time by the relative prospects of present and future reproductive success. As a consequence, animals of many species show flexible behavioral responses to environmental and social change. Here we show that disruption of the habitat of a colony of African cichlid fish, Haplochromis burtoni (Günther) caused males to switch social status more frequently than animals kept in a stable environment. H. burtoni males can be either reproductively active, guarding a territory, or reproductively inactive (nonterritorial). Although on average 25-50% of the males are territorial in both the stable and unstable environments, during the 20-week study, nearly two-thirds of the animals became territorial for at least 1 week. Moreover, many fish changed social status several times. Surprisingly, the induced changes in social status caused changes in somatic growth. Nonterritorial males and animals ascending in social rank showed an increased growth rate whereas territorial males and animals descending in social rank slowed their growth rate or even shrank. Similar behavioral and physiological changes are caused by social change in animals kept in stable environmental conditions, although at a lower rate. This suggests that differential growth, in interaction with environmental conditions, is a central mechanism underlying the changes in social status. Such reversible phenotypic plasticity in a crucial life-history trait may have evolved to enable animals to shift resources from reproduction to growth or vice versa, depending on present and future reproductive prospects.

Animals↗

PubMed2000

Density-dependent aposematism in the desert locust.

The ecological processes underlying locust swarm formation are poorly understood. Locust species exhibit phenotypic plasticity in numerous morphological, physiological and behavioural traits as their population density increases. These density-dependent changes are commonly assumed to be adaptations for migration under heterogeneous environmental conditions. Here we demonstrate that density-dependent nymphal colour change in the desert locust Schistocerca gregaria (Orthoptera: Acrididae) results in warning coloration (aposematism) when the population density increases and locusts consume native, toxic host plants. Fringe-toed lizards (Acanthodactylus dumerili (Lacertidae)) developed aversions to high-density-reared (gregarious-phase) locusts fed Hyoscyamus muticus (Solanaceae). Lizards associated both olfactory and visual cues with locust unpalatability, but only gregarious-phase coloration was an effective visual warning signal. The lizards did not associate low rearing density coloration (solitarious phase) with locust toxicity. Predator learning of density-dependent warning coloration results in a marked decrease in predation on locusts and may directly contribute to outbreaks of this notorious pest.

Animals↗

PubMed2003

Reproductive strategies in snakes.

Snakes of both sexes display remarkable flexibility and diversity in their reproductive tactics. Many features of reproduction in female snakes (such as reproductive mode and frequency, seasonality and multiple mating) allow flexible maternal control. For example, females can manipulate not only the genotypes of their offspring (through mate choice or enhanced sperm competition) but also the phenotypes of their offspring (through allocation 'decisions', behavioural and physiological thermoregulation, and nest-site selection). Reliance on stored energy ('capital') to fuel breeding results in low frequencies of female reproduction and, in extreme cases, semelparity. A sophisticated vomeronasal system not only allows male snakes to locate reproductive females by following scent trails, but also facilitates pheromonally mediated mate choice by males. Male-male rivalry takes diverse forms, including female mimicry and mate guarding; combat bouts impose strong selection for large body size in males of some species. Intraspecific (geographical) variation and phenotypic plasticity in a wide array of reproductive traits (offspring size and number; reproductive frequency; incidence of multiple mating; male tactics such as mate guarding and combat; mate choice criteria) provide exceptional opportunities for future studies.

Animals↗

PubMed2006

Personality plasticity after age 30.

Rank-order consistency of personality traits increases from childhood to age 30. After that, different summaries of the literature predict a plateau at age 30, or at age 50, or a curvilinear peak in consistency at age 50. These predictions were evaluated at group and individual levels using longitudinal data from the Guilford-Zimmerman Temperament Survey and the Revised NEO Personality Inventory for periods of up to 42 years. Consistency declined toward a nonzero asymptote with increasing time interval. Although some scales showed increasing stability after age 30, the rank-order consistencies of the major dimensions and most facets of the Five-Factor Model were unrelated to age. Ipsative stability, assessed with the California Adult Q-Set, also was unrelated to age. These data strengthen claims of predominant personality stability after age 30.

Adolescent↗

PubMed2005

Developmental plasticity in Macrophiothrix brittlestars: are morphologically convergent larvae also convergently plastic?

The pluteus larval forms of sea urchins (echinoids) and brittlestars (ophiuroids) use an internal skeleton to project arms that bear a long ciliated band used in swimming and feeding. The length of this ciliated band influences rates of maximum food clearance for larvae of both echinoderm classes and affects rates of growth and development in the plankton. Phylogenetic and morphological evidence, however, tend to support the view that the pluteus morphologies of the two classes are independently derived. Studies with echinoplutei have shown that investment in skeletal growth and ciliated band length changes in response to food conditions, with poorly fed larvae investing more in growth of the larval skeleton and arms either absolutely or in relation to other larval or developing postlarval structures. We present evidence for similar plasticity of skeletal growth in ophioplutei. We examined four species in the brittlestar genus Macrophiothrix that spanned a 3.8-fold range in egg size. Sibling larvae in 14 male-female crosses were reared with high (H) or low (L) food rations, and measurements were recorded for five skeletal arm rods and three non-arm body dimensions. The expression of adaptive plasticity (significantly longer arms in L versus H cultures on a given day) was apparent for most crosses in M. koehleri, the species with the smallest egg size. In the single cross for M. longipeda, larvae from L cultures had longer arms for their body length or stomach width than did larvae from H cultures. In these cases, plasticity was similar in timing, persistence, and magnitude to previously published results from echinoplutei. If internal skeletons are independently derived in the two classes, then plasticity in the expression of this homoplastic trait may itself be homoplastic.

Age Factors↗

PubMed2006

Phenotypic plasticity of body size in a temperate population of Drosophila melanogaster: when the temperature-size rule does not apply.

A natural population of Drosophila melanogaster in southern France was sampled in three different years and 10 isofemale lines were investigated from each sample. Two size-related traits, wing and thorax length, were measured and the wing/thorax ratio was also calculated. Phenotypic plasticity was analysed after development at seven different constant temperatures, ranging from 12 degrees C to 31 degrees C. The three year samples exhibited similar reaction norms, suggesting a stable genetic architecture in the natural population. The whole sample (30 lines) was used to determine precisely the shape of each reaction norm, using a derivative analysis. The practical conclusion was that polynomial adjustments could be used in all cases, but with different degrees: linear for the wing/thorax ratio, quadratic for thorax length, and cubic for wing length. Both wing and thorax length exhibited concave reaction norms, with a maximum within the viable thermal range. The temperatures of the maxima were, however, quite different, around 15 degrees C for the wing and 19.5 degrees C for the thorax. Assuming that thorax length is a better estimate of body size, it is not possible to state that increasing the temperature results in monotonically decreasing size (the temperature-size rule), although this is often seen to be the case for genetic variations in latitudinal clines. The variability of the traits was investigated at two levels-within and between lines-and expressed as a coefficient of variation. The within-line (environmental) variability revealed a regular, quadratic convex reaction norm for the three traits, with a minimum around 21 degrees C. This temperature of minimum variability may be considered as a physiological optimum, while extreme temperatures are stressful. The between-line (genetic) variability could also be adjusted to quadratic polynomials, but the curvature parameters were not significant. Our results show that the mean values of the traits and their variance are both plastic, but react in different ways along a temperature gradient. Extreme low or high temperatures decrease the size but increase the variability. These effects may be considered as a functional response to environmental stress.

Analysis of Variance↗

PubMed2006

Co-opting macrophage traits in cancer progression: a consequence of tumor cell fusion?

Tumor-associated macrophages (TAMs) play multiple roles in tumor initiation and progression. Tumors frequently appear in areas of chronic inflammation. This is likely aided by the mutagenic actions of macrophages. Tumor growth and progression is supported by macrophage-induced neoangiogenesis and stroma production, and macrophages produce tumor-stimulating growth factors. In most cancers a high density of TAMs predicts poor outcome. But not only do cancer cells depend upon macrophages for growth and invasion, they also co-opt macrophage traits. These include a wide diversity of molecules and pathways regulating adhesion, matrix alterations, neoangiogenesis, motility, chemotaxis, immune signaling pathways and even multidrug resistance proteins. Evidence is presented that these traits could be generated through macrophage-tumor cell fusion. Fusion has been reported in numerous animal tumor models and was recently documented in 2 human cases. Fusion could also account for the high degree of aneuploidy and plasticity in cancer, and for immune evasion. One common trait of myeloid-tumor fusion is the high expression of Beta1,6-branched N-glycans, used by macrophages in systemic migration. Beta1,6-branched oligosaccharides have long been associated with metastasis in animal models and were recently found to be common in a wide diversity of human cancers. We suggest that Beta1,6-branched oligosaccharides in human cancer may reflect widespread tumor cell fusion. Viewing the cancer cell as a myeloid hybrid provides new approaches towards understanding and treating this complex disease.

Bone Marrow Neoplasms↗

PubMed2007

Correlated responses to artificial body size selection in growth, development, phenotypic plasticity and juvenile viability in yellow dung flies.

Most life history traits are positively influenced by body size, whereas disadvantages of large body size are poorly documented. To investigate presumed intrinsic costs of large size in the yellow dung fly (Scathophaga stercoraria; Diptera: Scathophagidae), we established two replicates each of three body size laboratory selection lines (small, control and large; selection on males only), and subjected flies of the resulting extended body size range to various abiotic stresses. Response to selection was symmetrical in the small and large lines (realized h(2) = 0.16-0.18). After 24 generations of selection body size had changed by roughly 10%. Female size showed a correlated response to selection on male size, whereas sexual size dimorphism did not change. Development time also showed a correlated response as, similar to food limited flies, small line flies emerged earlier at smaller body size. At the lowest larval food limit possible, flies of all lines emerged at the same small body size after roughly the same development time; so overall phenotypic plasticity in body size and development time strongly increased following selection. Juvenile mortality increased markedly when food was extremely limited, large line flies showing highest mortality. Winter frost disproportionately killed large (line) flies because of their longer development times. Mortality at high temperatures was high but size-selective effects were inconsistent. In all environments the larger males suffered more. Initial growth rate was higher for males and at unlimited food. Small line individuals of both sexes grew slowest at unlimited larval food but fastest at limited larval food, suggesting a physiological cost of fast growth. Overall, extension of the natural body size range by artificial selection revealed some otherwise cryptic intrinsic juvenile viability costs of large size, mediated by longer development or faster growth, but only in stressful environments.

Animal Nutritional Physiological Phenomena↗