105 resultados para Morphological traits


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1. The presence of an across-species trade-off between dispersal ability and competitive ability has been proposed as a mechanism that facilitates coexistence. It is not clear if a similar trade-off exists within species. Such a trade-off would constrain the evolution of either trait and, given appropriate selection pressures, promote local adaptation in these traits. 2. This study found substantial levels of heritable variation in competitive ability of the pea aphid, Acyrthosiphon pisum Harris (Homoptera: Aphididae), measured in terms of relative survival when reared with a single clone of the vetch aphid, Megoura viciae Buckton (Homoptera: Aphididae). 3. Pea aphids can move to new patches by either flying (longer distance dispersal) or walking (local dispersal) from plant to plant. There was considerable clonal variation in dispersal ability, measured in terms of the proportion of winged offspring produced, and ability to survive away from their host plant. 4. Winged individuals showed longer off-plant survival times than wingless forms of the same pea aphid clone. 5. There was no evidence of a relationship between clonal competitive ability and either measure of dispersal ability, although the power of the test is limited by the number of pea aphid clones used in the trial. 6. However, there was a positive correlation between clonal fecundity and the proportion of winged offspring produced. Although speculative, it is suggested that clones that are more likely to either overwhelm their host plant or attract higher numbers of natural enemies as a result of having higher fecundity are more likely to produce winged morphs.

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There are about 141 described species of Licuala. Structurally, the genus has very consistent vegetative and fertile characters. As the genus undergoes revision, it is becoming clear that it contains great morphological variation within the strict vegetative and reproductive character constraints found in the genus. This paper describes the variation found in the genus and its significance in taxon delimitation.

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The solvent-induced transition between self-assembled structures formed by the peptide AAKLVFF is studied via electron microscopy, light scattering, and spectroscopic techniques. The peptide is based on a core fragment of the amyloid beta-peptide, KLVFF, extended by two alanine residues. AAKLVFF exhibits distinct structures of twisted fibrils in water or nanotubes in methanol. For intermediate water/methanol compositions, these structures are disrupted and replaced by wide filamentous tapes that appear to be lateral aggregates of thin protofilaments. The orientation of the beta-strands in the twisted tapes or nanotubes can be deduced from X-ray diffraction on aligned stalks, as well as FT-IR experiments in transmission compared to attenuated total reflection. Strands are aligned perpendicular to the axis of the twisted fibrils or the nanotubes. The results are interpreted in light of recent results on the effect of competitive hydrogen bonding upon self-assembly in soft materials in water/methanol mixtures.

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A series of self-assembling terminally blocked tripeptides (containing coded amino acids) form gels in various aromatic solvents including benzene, toluene, xylenes at low concentrations. However these tripeptides do not form gels in aliphatic hydrocarbons like n-hexane, cyclohexane, n-decane etc. Morphological studies of the dried gel indicate the presence of an entangled fibrous network, which is responsible for gelation. Differential scanning calorimetric (DSC) studies of the gels produced by peptide 1 clearly demonstrates thermoreversible nature of the gel and tripeptide-solvent complex may be produced during gel formation. FT-IR and H-1 NMR studies of the gels demonstrate that an intermolecular hydrogen-bonding network is formed during gelation. Single crystal X-ray diffraction studies for peptides 1, 2 and 3 have been performed to investigate the molecular arrangement that might be responsible for forming the fibrous network of these self-assembling peptide gelators. It has been found that the morph responsible for gelation of peptides 1, 2 and 3 in benzene is somewhat different from that of its xerogel.

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Developmental and biophysical leaf characteristics that influence post-harvest shelf life in lettuce, an important leafy crop, have been examined. The traits were studied using 60 informative F-9 recombinant inbed lines (RILs) derived from a cross between cultivated lettuce (Lactuca sativa cv. Salinas) and wild lettuce (L. serriola acc. UC96US23). Quantitative trait loci (QTLs) for shelf life co-located most closely with those for leaf biophysical properties such as plasticity, elasticity, and breakstrength, suggesting that these are appropriate targets for molecular breeding for improved shelf life. Significant correlations were found between shelf life and leaf size, leaf weight, leaf chlorophyll content, leaf stomatal index, and epidermal cell number per leaf, indicating that these pre-harvest leaf development traits confer post-harvest properties. By studying the population in two contrasting environments in northern and southern Europe, the genotype by environment interaction effects of the QTLs relevant to leaf development and shelf life were assessed. In total, 107 QTLs, distributed on all nine linkage groups, were detected from the 29 traits. Only five QTLs were common in both environments. Several areas where many QTLs co-located (hotspots) on the genome were identified, with relatively little overlap between developmental hotspots and those relating to shelf life. However, QTLs for leaf biophysical properties (breakstrength, plasticity, and elasticity) and cell area correlated well with shelf life, confirming that the ideal ideotype lettuce should have small cells with strong cell walls. The identification of QTLs for leaf development, strength, and longevity will lead to a better understanding of processability at a genetic and cellular level, and allow the improvement of salad leaf quality through marker-assisted breeding.

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The relationship between a loss of viability and several morphological and physiological changes was examined with Escherichia coli strain J1 subjected to high-pressure treatment. The pressure resistance of stationary-phase cells was much higher than that of exponential-phase cells, but in both types of cell, aggregation of cytoplasmic proteins and condensation of the nucleoid occurred after treatment at 200 MPa for 8 min. Although gross changes were detected in these cellular structures, they were not related to cell death, at least for stationary-phase cells. In addition to these events, exponential-phase cells showed changes in their cell envelopes that were not seen for stationary-phase cells, namely physical perturbations of the cell envelope structure, a loss of osmotic responsiveness, and a loss of protein and RNA to the extracellular medium. Based on these observations, we propose that exponential-phase cells are inactivated under high pressure by irreversible damage to the cell membrane. In contrast, stationary-phase cells have a cytoplasmic membrane that is robust enough to withstand pressurization up to very intense treatments. The retention of an intact membrane appears to allow the stationary-phase cell to repair gross changes in other cellular structures and to remain viable at pressures that are lethal to exponential-phase cells.

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The authors examined caregivers' characteristics and experiences. Previously suggested principles for identifying the primary caregiver in 22 multiple-caregiver families were assessed, but none reliably distinguished the primary caregiver. The authors then compared primary (n = 22), nonprimary (n = 22), and lone caregivers' (n = 43) appraisals of caregiving and psychological distress. Lone and primary caregivers' experiences were similar. but nonprimary caregivers' experiences were less adverse. Despite these findings, greater psyhcological distress in primary caregivers indicated greater psychological distress in nonprimary caregivers.

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International Perspective The development of GM technology continues to expand into increasing numbers of crops and conferred traits. Inevitably, the focus remains on the major field crops of soybean, maize, cotton, oilseed rape and potato with introduced genes conferring herbicide tolerance and/or pest resistance. Although there are comparatively few GM crops that have been commercialised to date, GM versions of 172 plant species have been grown in field trials in 31 countries. European Crops with Containment Issues Of the 20 main crops in the EU there are four for which GM varieties are commercially available (cotton, maize for animal feed and forage, and oilseed rape). Fourteen have GM varieties in field trials (bread wheat, barley, durum wheat, sunflower, oats, potatoes, sugar beet, grapes, alfalfa, olives, field peas, clover, apples, rice) and two have GM varieties still in development (rye, triticale). Many of these crops have hybridisation potential with wild and weedy relatives in the European flora (bread wheat, barley, oilseed rape, durum wheat, oats, sugar beet and grapes), with escapes (sunflower); and all have potential to cross-pollinate fields non-GM crops. Several fodder crops, forestry trees, grasses and ornamentals have varieties in field trials and these too may hybridise with wild relatives in the European flora (alfalfa, clover, lupin, silver birch, sweet chestnut, Norway spruce, Scots pine, poplar, elm, Agrostis canina, A. stolonifera, Festuca arundinacea, Lolium perenne, L. multiflorum, statice and rose). All these crops will require containment strategies to be in place if it is deemed necessary to prevent transgene movement to wild relatives and non-GM crops. Current Containment Strategies A wide variety of GM containment strategies are currently under development, with a particular focus on crops expressing pharmaceutical products. Physical containment in greenhouses and growth rooms is suitable for some crops (tomatoes, lettuce) and for research purposes. Aquatic bioreactors of some non-crop species (algae, moss, and duckweed) expressing pharmaceutical products have been adopted by some biotechnology companies. There are obvious limitations of the scale of physical containment strategies, addressed in part by the development of large underground facilities in the US and Canada. The additional resources required to grow plants underground incurs high costs that in the long term may negate any advantage of GM for commercial productioNatural genetic containment has been adopted by some companies through the selection of either non-food/feed crops (algae, moss, duckweed) as bio-pharming platforms or organisms with no wild relatives present in the local flora (safflower in the Americas). The expression of pharmaceutical products in leafy crops (tobacco, alfalfa, lettuce, spinach) enables growth and harvesting prior to and in the absence of flowering. Transgenically controlled containment strategies range in their approach and degree of development. Plastid transformation is relatively well developed but is not suited to all traits or crops and does not offer complete containment. Male sterility is well developed across a range of plants but has limitations in its application for fruit/seed bearing crops. It has been adopted in some commercial lines of oilseed rape despite not preventing escape via seed. Conditional lethality can be used to prevent flowering or seed development following the application of a chemical inducer, but requires 100% induction of the trait and sufficient application of the inducer to all plants. Equally, inducible expression of the GM trait requires equally stringent application conditions. Such a method will contain the trait but will allow the escape of a non-functioning transgene. Seed lethality (‘terminator’ technology) is the only strategy at present that prevents transgene movement via seed, but due to public opinion against the concept it has never been trialled in the field and is no longer under commercial development. Methods to control flowering and fruit development such as apomixis and cleistogamy will prevent crop-to-wild and wild-to-crop pollination, but in nature both of these strategies are complex and leaky. None of the genes controlling these traits have as yet been identified or characterised and therefore have not been transgenically introduced into crop species. Neither of these strategies will prevent transgene escape via seed and any feral apomicts that form are arguably more likely to become invasives. Transgene mitigation reduces the fitness of initial hybrids and so prevents stable introgression of transgenes into wild populations. However, it does not prevent initial formation of hybrids or spread to non-GM crops. Such strategies could be detrimental to wild populations and have not yet been demonstrated in the field. Similarly, auxotrophy prevents persistence of escapes and hybrids containing the transgene in an uncontrolled environment, but does not prevent transgene movement from the crop. Recoverable block of function, intein trans-splicing and transgene excision all use recombinases to modify the transgene in planta either to induce expression or to prevent it. All require optimal conditions and 100% accuracy to function and none have been tested under field conditions as yet. All will contain the GM trait but all will allow some non-native DNA to escape to wild populations or to non-GM crops. There are particular issues with GM trees and grasses as both are largely undomesticated, wind pollinated and perennial, thus providing many opportunities for hybridisation. Some species of both trees and grass are also capable of vegetative propagation without sexual reproduction. There are additional concerns regarding the weedy nature of many grass species and the long-term stability of GM traits across the life span of trees. Transgene stability and conferred sterility are difficult to trial in trees as most field trials are only conducted during the juvenile phase of tree growth. Bio-pharming of pharmaceutical and industrial compounds in plants Bio-pharming of pharmaceutical and industrial compounds in plants offers an attractive alternative to mammalian-based pharmaceutical and vaccine production. Several plantbased products are already on the market (Prodigene’s avidin, β-glucuronidase, trypsin generated in GM maize; Ventria’s lactoferrin generated in GM rice). Numerous products are in clinical trials (collagen, antibodies against tooth decay and non-Hodgkin’s lymphoma from tobacco; human gastric lipase, therapeutic enzymes, dietary supplements from maize; Hepatitis B and Norwalk virus vaccines from potato; rabies vaccines from spinach; dietary supplements from Arabidopsis). The initial production platforms for plant-based pharmaceuticals were selected from conventional crops, largely because an established knowledge base already existed. Tobacco and other leafy crops such as alfalfa, lettuce and spinach are widely used as leaves can be harvested and no flowering is required. Many of these crops can be grown in contained greenhouses. Potato is also widely used and can also be grown in contained conditions. The introduction of morphological markers may aid in the recognition and traceability of crops expressing pharmaceutical products. Plant cells or plant parts may be transformed and maintained in culture to produce recombinant products in a contained environment. Plant cells in suspension or in vitro, roots, root cells and guttation fluid from leaves may be engineered to secrete proteins that may be harvested in a continuous, non-destructive manner. Most strategies in this category remain developmental and have not been commercially adopted at present. Transient expression produces GM compounds from non-GM plants via the utilisation of bacterial or viral vectors. These vectors introduce the trait into specific tissues of whole plants or plant parts, but do not insert them into the heritable genome. There are some limitations of scale and the field release of such crops will require the regulation of the vector. However, several companies have several transiently expressed products in clinical and pre-clinical trials from crops raised in physical containment.

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During spray drying, emphasis is placed on process optimisation to generate favourable particle morphological and flow properties. The effect of the initial feed solution composition on the drug release from the prepared microparticles is rarely considered. We investigated the effects of solvent composition, feed solution concentration and drug-loading on sodium salicylate, hydrocortisone and triamcinolone release from spray dried Eudragit L100 microparticles. Eudragit L100 is a pH-responsive polymer whose dissolution threshold is pH 6 so dissolution testing of the prepared microparticles at pH 5 and 1.2 illustrated non-polymer controlled burst release. Increasing the water content of the initial ethanolic feed solution significantly reduced hydrocortisone burst release at pH 5, as did reducing the feed solution concentration. These findings caution that changes in feed solution concentration or solvent composition not only affect particles’ morphological characteristics but can also negatively alter their drug release properties. This work also illustrate that drug-free microparticles can have different morphological properties to drug-loaded microparticles. Therefore, process optimisation needs to be carried out using drug-loaded systems. Depending on the physicochemical properties of the encapsulated API, drug-loading can affect the polymer solubility in the initial feed solution with consequent impact on microparticles morphological and release properties.

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The photosynthetic characteristics of eight contrasting cocoa genotypes were studied with the aim of examining genotypic variation in maximum (light-saturated) photosynthetic rates, light-response curve parameters and water use efficiency. Photosynthetic traits were derived from single leaf gas exchange measurements using a portable infra-red gas analyser. All measurements were conducted in a common greenhouse environment. Significant variation was observed in light-saturated photosynthesis ranging from 3.4 to 5.7 µmol CO2 m-2 s-1 for the clones IMC 47 and SCA 6, respectively. Furthermore, analyses of photosynthetic light response curves indicated genotypic differences in light saturation point and quantum efficiency (i.e. the efficiency of light use). Stomatal conductance was a significant factor underlying genotypic differences in assimilation. Genotypic variation was also observed in a number of leaf traits, including specific leaf area (the ratio of leaf area to leaf weight), chlorophyll concentration and nitrogen content. There was a positive correlation between leaf nitrogen per unit area and light-saturated photosynthesis. Water use efficiency, defined as the ratio of photosynthetic rate to transpiration rate, also varied significantly between clones (ranging from 3.1 mmol mol-1 H2O for the clone IMC 47 to 4.2 mmol mol-1 H2O for the clone ICS 1). Water use efficiency was a negative function of specific leaf area, suggesting that low specific leaf area might be a useful criterion for selection for increased water use efficiency. It is concluded that both variation in water use efficiency and the photosynthetic response to light have the potential to be exploited in breeding programmes.

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The human mirror neuron system (hMNS) is believed to provide a basic mechanism for social cognition. Event-related desynchronization (ERD) in alpha (8–12 Hz) and low beta band (12–20 Hz) over sensori-motor cortex has been suggested to index mirror neurons' activity. We tested whether autistic traits revealed by high and low scores on the Autistic Quotient (AQ) in the normal population are linked to variations in the electroencephalogram (EEG) over motor, pre-motor cortex and supplementary motor area (SMA) during action observation. Results revealed that in the low AQ group, the pre-motor cortex and SMA were more active during hand action than static hand observation whereas in the high AQ group the same areas were active both during static and hand action observation. In fact participants with high traits of autism showed greater low beta ERD while observing the static hand than those with low traits and this low beta ERD was not significantly different when they watched hand actions. Over primary motor cortex, the classical alpha and low beta ERD during hand actions relative to static hand observation was found across all participants. These findings suggest that the observation–execution matching system works differently according to the degree of autism traits in the normal population and that this is differentiated in terms of the EEG according to scalp site and bandwidth.