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The Lucy Mission to the Trojan asteroids in Jupiter's orbit carries an instrument named L'Ralph, a visible/near infrared multi-spectral imager and a short wavelength infrared hyperspectral imager. It is one of the core instruments on Lucy, NASA's first mission to the Trojans. L'Ralph's primary purpose is to map the surface geology and composition of these objects, but it will also be used to search for possible tenuous exospheres. It is compact, low mass (32.3 kg), power efficient (24.5 W), and robust with high sensitivity and excellent imaging. These characteristics, and its high degree of redundancy, make L'Ralph ideally suited to this long-duration multi-flyby reconnaissance mission. [ABSTRACT FROM AUTHOR]

The earliest cell fate decisions in a developing embryo are those associated with establishing the germ layers. The specification of the mesoderm and endoderm is of particular interest as the mesoderm is induced from the endoderm, potentially from an underlying bipotential group of cells, the mesendoderm. Mesendoderm formation has been well studied in an amphibian model frog, Xenopus laevis, and its formation is driven by a gene regulatory network (GRN) induced by maternal factors deposited in the egg. We have recently demonstrated that the axolotl, a urodele amphibian, utilises a different topology in its GRN to specify the mesendoderm. In this paper, we develop spatially structured mathematical models of the GRNs governing mesendoderm formation in a line of cells. We explore several versions of the model of mesendoderm formation in both Xenopus and the axolotl, incorporating the key differences between these two systems. Model simulations are able to reproduce known experimental data, such as Nodal expression domains in Xenopus, and also make predictions about how the positional information derived from maternal factors may be interpreted to drive cell fate decisions. We find that whilst cell-cell signalling plays a minor role in Xenopus, it is crucial for correct patterning domains in axolotl. [ABSTRACT FROM AUTHOR]

Nodal signals are key regulators of mesoderm and endoderm development in vertebrate embryos. It has been observed experimentally that in Xenopus embryos the spatial range of Nodal signals is restricted by the signal Antivin (also known as Lefty). Nodal signals can activate both Nodal and Antivin, whereas Antivin is thought to antagonise Nodal by binding either directly to it or to its receptor. In this paper we develop a mathematical model of this signalling network in a line of cells. We consider the heterodimer and receptor-mediated inhibition mechanisms separately and find that, in both cases, the restriction by Antivin to the range of Nodal signals corresponds to wave pinning in the model. Our analysis indicates that, provided Antivin diffuses faster than Nodal, either mechanism can robustly account for the experimental data. We argue that, in the case of Xenopus development, it is wave pinning, rather than Turing-type patterning, that is underlying Nodal–Antivin dynamics. This leads to several experimentally testable predictions, which are discussed. Furthermore, for heterodimer-mediated inhibition to prevent waves of Nodal expression from propagating, the Nodal–Antivin complex must be turned over, and diffusivity of the complex must be negligible. In the absence of molecular mechanisms regulating these, we suggest that Antivin restricts Nodal signals via receptor-mediated, and not heterodimer-mediated, inhibition. [ABSTRACT FROM AUTHOR]

The seed-specific expression of recombinant proteins in transgenic plants offers several interesting advantages over other production platforms. The aim of this study was to select accessions of Arabidopsis thaliana with the highest potential as a platform for seed-specific production of recombinant proteins. A. thaliana was chosen because of its flexibility, high seed yield per m², high natural protein content and its non-food status. Seven characteristics were measured for 96 accessions; days to first flower bud, days to complete senescence, rosette size, number of main bolts, dry biomass of plant, seed yield and protein content of seeds. Three characteristics (length of life cycle, seed yield and protein content) were used to select accessions with a maximal yield. A variation of length of life cycle between 87 ± 11 days (Ler-1) and more than 200 days (several accessions) was registered. Seed yields per accession varied between 18 ± 16 mg (Wa-1) and 274 ± 76 mg (Mr-0). Protein content ranged between 30% (Ws-2) and 38% (Cvi-0). Based on the results of this study, accession Nok-3 is selected as the accession best suited for exploitation as a seed-based platform for the production of recombinant proteins. Nok-3 has a high seed yield (194 ± 66 mg) combined with a moderate protein content of 34.8% and short life cycle of 126 ± 17 days, resulting in a calculated protein yield per year three times higher than reference accession Col-0. In conclusion, this study illustrates the unexploited variability present in the Arabidopsis gene pool that can be used directly for further optimization of Arabidopsis seeds as production platform. In combination with A. thaliana's rapid life cycle, flexibility, and high fertility, this makes it an attractive platform for the production of specific groups of recombinant proteins, such as high-purity products produced on a relatively small scale. [ABSTRACT FROM AUTHOR]

This study aimed at determining whether transgene expression variability is observed in single-copy T-DNA plants and whether it can be correlated with the T-DNA integration position. Among a population of 135Arabidopsis thalianatransformants, selected on the basis of antibiotic resistance marker expression, 21 single-copy T-DNA transformants were identified and characterized. In 19 of these 21 lines, 35S-ß-glucuronidase transgene expression, measured in two subsequent generations, was similar. This observation means that the intra-transformant variability was as high as the inter-transformant variability. Integration into an intergenic or genic region, into an exon or intron, in sense or antisense orientation, did not result in differential transgene expression. Remarkably, single-copy transformants were not always the highest expressers, implying that low transgene expression is not always induced by multicopy transformants. In only 2 of the 21 single-copy plants was the transgene expression more than 20-fold lower. However, characteristics of the insertion position in one of these lines did not differ significantly when compared to high-expressing lines. In the remaining line, methylation of the transgene was clearly demonstrated. In conclusion, screening for single-copy T-DNA transformants greatly enriches for stable and high transgene expression, because the integration position is not a major determinant of transgene expression variability inArabidopsis. [ABSTRACT FROM AUTHOR]

The nuclear genetic variation within and between four sessile (Q. petraea) and six pedunculate (Q. robur) autochthonous Flemish oak populations was investigated with AFLP markers. One sessile and one pedunculate oak population were additionally screened for detailed leaf characteristics using an image analysis system. Principal coordinate analysis on the AFLP data classified the oaks in two main groups, according to their taxonomic status. No species-specific AFLP markers were found using four primer combinations, but marker frequency differences up to 71% were recorded between both species. Analysis of the genetic structure showed that the divergence between species, as observed by ordination, was significant. Both species revealed similar diversity levels. A smaller though significant differentiation was also revealed for both species among populations within species. Molecular and morphology based approaches showed a high degree of consistency. Screening of 60 AFLP primer combinations using a bulking strategy did not allow identifying species-specific markers, which supports the conclusions reached in previous studies. The distribution of genetic variability at the species and at the population level is discussed. [ABSTRACT FROM AUTHOR]

A T-DNA fingerprinting method is presented based on amplified fragmentlength polymorphism with an anchored polymerase chain reaction step. Thismethod allows discrimination between different T-DNA inserts in stablytransformed plants. The technique was evaluated by analyzing 51 transgenic Arabidopsis lines that had been characterized in detail by genomicblotting. Comparison of the obtained fingerprints with the availableintegration information demonstrated that fingerprints were correlated tothe predicted patterns, except for the inverted repeat junctions and forthose inserts with large deletions at the left or right border. Ourexperiments show that by using T-DNA fingerprinting multi-copy transgeniclines can be eliminated efficiently so that the technique can be used toenrich a population of transgenic plants for putative single-copytransformants. [ABSTRACT FROM AUTHOR]

Three approaches for addressing criteria for Distinctness, Uniformity and Stability (DUS) assessment by means of AFLP data are presented. AFLP data were obtained for three consecutive seed deliveries of 15 sugar beet varieties that were under investigation for the official Belgian list (’93, ’94 and ’95). In total, 696 AFLP markers were scored on 1350 plants. As a first approach, a cluster analysis based on Nei’s standard genetic distances between varieties and/or seed deliveries was made. Three major groups put together varieties belonging to corresponding breeding programmes. Statistical procedures, involving bootstrapping and random sampling of subsets of markers, were applied to test the reproducibility of the ordinations and the redundancy present in the data set. In a second approach, the genetic structure inferred by varieties and seed deliveries was submitted to an Analysis of Molecular Variance (AMOVA). Major genetic variation was attributed to individual plant differences within seed deliveries. Differences among seed deliveries seemed to be as important as differences among varieties or breeding programmes. Individual plant data were used for assignment tests. The computation of the assignment was based on the ranking of individual genotypes to one other (based on Jaccard similarity coefficients). The distribution over the accessions for each variety or seed delivery was used to check what group of plants each individual is genetically most similar to. Varieties were classified according to the degree to which the distribution over the different accessions was mainly allocated to their appropriate seed deliveries (from the same variety) or cross- allocated to other varieties. Criteria for DUS-evaluation could be set by each of the approaches; it is discussed in what way the result obtained differs and agrees. [ABSTRACT FROM AUTHOR]

A sample set of registered perennial ryegrass varieties was used to compare how morphological characterisation and AFLP® (AFLP® is a registered trademark of Keygene N.V.) and STS molecular markers described variety relationships. All the varieties were confirmed as morphologically distinct, and both the STS and AFLP markers exposed sufficient genetic diversity to differentiate these registered ryegrass varieties. Distances obtained by each of the approaches were compared, with special attention given to the coincidences and divergences between the methods. When correlations between morphological, AFLP and STS distances were calculated and the corresponding scatter-plots constructed, the variety relationships appeared to be rather inconsistent across the methods, especially between morphology and the molecular markers. However, some consistencies were found for closely related material. An implication could be that these molecular-marker techniques, while not yet suited to certain operations in the traditional registration of new varieties, could be suitable methods for investigating disputable distinctness situations or possible EDV (EDV= essentially derived variety. An EDV is a variety being clearly distinct from, but conforming in the expression of the essential characteristics of, an ’initial variety’ (IV) from which it is found to have been predominantly derived) relationships, subject to establishing standardised protocols and statistical techniques. Some suggestions for such a protocol, including a statistical test for distinctness, are given. [ABSTRACT FROM AUTHOR]

Flower colour variegation is not only a phenomenon of importance to horticulture, the phenotype involved is also often used as a scientific model system for the study of complex gene regulation processes. In the course of such studies on azalea, we observed a correlation between flower colour patterns, flower morphology and somatic polyploidy. Using high-resolution flow cytometry of nuclear DNA, the ploidy level was determined in flowers of different azalea sport families. Sports exhibiting variegated flowers with broad (>7 mm), differently coloured, petal edges (picotee type) proved to be tetraploid in the petal edge but diploid in the rest of the flower tissue. Neither flower colour pattern nor ploidy differences are periclinal chimeric in origin, but seem to be correlated with the topographic location of the cells within the flower tissue, i.e. the margin of the petals. The possible role of gene dosage effects and cell size involved in the remarkable correlation between somatic polyploidy, (flavonoid) gene expression and flower morphology is discussed. [ABSTRACT FROM AUTHOR]

The concept of genetic conformity lies at the basis of the definition of essential derivation, or the process of using a protected variety (or `initial variety', IV) as the base to develop another similar variety (the essentially derived variety, EDV). Methods based on morphology, biochemistry or on molecular markers can be used to estimate genetic conformity. In this study, the capability of AFLP®1 markers to provide a reliable and meaningful estimate of genetic conformity of different varieties was investigated in diploid perennial ryegrass ( Lolium perenne spp.), an allogamous species whose varieties are genetically heterogeneous. Twelve accessions with known breeding lineage, comprising five closely related groups, were included in the study. For the set of test accessions analysed, the AFLP protocol accurately reproduced the same relationships as were evident from examining their morphology and both these results were consistent with the relationships known to exist within the different test groups. Principal components analysis as well as cluster analysis associated unambiguously the IV and the EDV accessions. It was concluded that the methodology developed in this study could be used as a model from which to create a protocol for evaluating putative cases of essential derivation. [ABSTRACT FROM AUTHOR]

In this study the morphological and protein diversity of twelve diploid perennial ryegrass accessions ( Lolium perenne L.) was examined. These accessions comprised five closely related groups, each containing an `initial variety' (IV) and one or more declared `essentially derived varieties' (EDV), with differing degrees of relatedness. `Essential derivation' is a legal concept relating to intellectual property in plant varieties and is additional to Plant Breeders Rights (PBR). An EDV is defined as clearly distinct from, but conforming in its expression of the essential characteristics of an IV, from which it is found to have been predominantly derived. Where an essential derivation has been confirmed, the breeder of the IV may be entitled to some royalty sharing of the EDV. Clearly, therefore, in any successful EDV claim, evidence of a high degree of conformity in either the phenotype or genotype would be required. Examination of plant morphology indicated that all the EDVs were morphologically distinct from their corresponding IV in one or more morphological characteristic. using a principal co-ordinates analysis to give an overall measure of morphological difference, all twelve accessions were correctly clustered into their related groups and the magnitude of the differences within groups reflected their known breeding histories. Examining protein diversity by methods that targeted single- and multiple-locus genes also clustered the accessions into their correct groups, in most cases. However, only by examining diversity in seed storage proteins were within-group relationships accurately represented. The methods used provided no consistent representation of between-group relationships. It was concluded that the morphological method provided a creditable measure of genetic conformity, but to avoid incurring excessive time, work and cost, results from existing national PBR trials would need to be openly available. Within the limits of the genetic material examined, seed storage protein diversity appeared to provide a suitable combination of accuracy and efficiency on which to base a routine test. However, given more complex breeding relationships than those in this study, methods such as AFLP1 markers that sample more genetic diversity, may be necessary to maintain this level of accuracy. [ABSTRACT FROM AUTHOR]

The genetic relationships between and within Hibiscus syriacus, Hibiscus sinosyriacus and Hibiscus paramutabilis, three winter hardy Hibiscus species native to China, were analysed by the amplified fragment length polymorphisms (AFLP) technique and by morphological evaluation of flower and leaf characteristics. Both methods clearly discriminated between the three species. H. sinosyriacus was classified as an intermediate form between H. paramutabilis and H. syriacus; however, it showed a higher similarity to H. paramutabilis. The different H. syriacus cultivars could be identified by AFLP analysis, while also leaf indices clustered the different cultivars in small groups. Flow cytometry showed that both triploid and tetraploid cultivars occur in the H. syriacus assortment. In general triploid cultivars had larger flowers compared to diploid cultivars. [ABSTRACT FROM AUTHOR]

An evaluation was performed of the potential use of AFLP markers to reveal polymorphisms among Lolium perenne plants with different degrees of kinship. Radioactive and fluorescent detection techniques were applied. The use of a fluorescent detection approach contributed greatly to the speed and ease of conducting and interpreting the AFLP patterns. The great discriminative power of AFLP markers and their capacity to represent genetic relationships among ryegrass plants was shown. Despite the high polymorphic value of the AFLP markers, standard statistical tests could not differentiate between two gene pools derived from different breeding programmes. It proved also impossible to correlate fodder and turf phenotypes with AFLP distance data. A very important point revealed by our data is the high degree of genetic diversity within commercial ryegrass varieties. Our findings are relevant to any outcrossing crop with a breeding strategy based on the production of synthetic populations. [ABSTRACT FROM AUTHOR]

Fluorescent AFLP and automated data analysis were employed to assess the genetic conformity within a breeders’ collection of evergreen azaleas. The study included 75 genotypes of Belgian pot azaleas ( Rhododendron simsii Planch. hybrids), Kurume and Hirado azaleas and wild ancestor species from the Tsutsusi subgenus. Fluorescent detection and addition of an internal size standard to each lane enabled the automated scoring of each fragment arising from a single AFLP primer combination (PC). The use of three PCs generated an initial data set with a total of 648 fragments ranging from 70 bp to 450 bp. Different marker selection thresholds for average fluorescent signal intensity and marker frequency were used to create eight extra restricted data subsets. Pairwise plant genetic similarity was calculated for the nine data sets using the Simple Matching coefficient (symmetrical, including double-zeros) and Jaccard coefficient (asymmetrical, excluding double zeros). The averages, the ranges and the correlation to one other (Mantel analysis) were compared for the obtained similarity matrices. This revealed the sensitivity of ordinations obtained by both similarity coefficients for the presence of weak or intensive markers or for the degree of polymorphism of the markers. For 34 cultivars, pedigree information (at maximum to the fifth ancestor generation) was available. Genetic similarity by descent (kinship coefficient) was turned into a genetic distance and correlated to the genetic conformity, as revealed by the different selections of AFLP markers (Mantel analysis). Use of a Simple Matching coefficient with no or moderate selection to signal intensity and excluding rare and abundant markers gave the best correlation with pedigree. Finally, the ordination of the studied genotypes by means of dendrograms and principal co-ordinate analysis was confronted with known or accepted relationships based on geographical origin, parentage and morphological characters. Genotypes could be assigned to three distinct groups: pot azaleas, Kurume azaleas and Hirado azaleas. Wild ancestor species appeared to be more related to the Japanese azaleas. Intermediate cultivars could be typified as crossings with Kurume or Hirado azaleas or with wild species. [ABSTRACT FROM AUTHOR]

Using pharmacokinetic data from healthy human volunteers in a bicompartmental pharmacokinetic model, a repeated dose scheme for pralidoxime methylsulphate (Contrathion) was developed producing plasma levels remaining above the assumed 'therapeutic concentration' of 4 mg·1. Using the same data, it was found that a concentration of 4 mg · 1 could also be obtained by a loading dose of 4.42 mg · kg followed by a maintenance dose of 2.14 mg · kg · h. In order to study the pharmacokinetic behaviour of pralidoxime in poisoned patients, this continuous infusion scheme was then applied in nine cases of organophosphorus poisoning (agents: ethyl parathion, ethyl and methyl parathion, dimethoate and bromophos), and the pralidoxime plasma levels were determined. The mean plasma levels obtained in the various patients varied between 2.12 and 9 mg·1. Pharmacokinetic data were calculated, giving a total body clearance of 0.57±0.271· kg· h (mean ± SD), an elimination half-life of 3.44±0.90 h, and a volume of distribution of 2.77±1.451 ·kg. [ABSTRACT FROM AUTHOR]