Jesús Rodríguez Fernández

Identification of the Major Sex-Determining Region of Turbot ( Scophthalmus maximus )

Sex determination in fish is a labile character in evolutionary terms. The sex-determining (SD) master gene can differ even between closely related fish species. This group is an interesting model for studying the evolution of the SD region and the gonadal differentiation pathway. The turbot (Scophthalmus maximus) is a flatfish of great commercial value, where a strong sexual dimorphism exists for growth rate. Following a QTL and marker association approach in five families and a natural population, we identified the main SD region of turbot at the proximal end of linkage group (LG) 5, close to the SmaUSC-E30 marker. The refined map of this region suggested that this marker would be 2.6 cM and 1.4 Mb from the putative SD gene. This region appeared mostly undifferentiated between males and females, and no relevant recombination frequency differences were detected between sexes. Comparative genomics of LG5 marker sequences against five model species showed no similarity of this chromosome to the sex chromosomes of medaka, stickleback, and fugu, but suggested a similarity to a sex-associated QTL from Oreochromis spp. The segregation analysis of the closest markers to the SD region demonstrated a ZW/ZZ model of sex determination in turbot. A small proportion of families did not fit perfectly with this model, which suggests that other minor genetic and/or environmental factors are involved in sex determination in this species.

QTL detection for Aeromonas salmonicida resistance related traits in turbot ( Scophthalmus maximus )

BackgroundInteractions between fish and pathogens, that may be harmless under natural conditions, often result in serious diseases in aquaculture systems. This is especially important due to the fact that the strains used in aquaculture are derived from wild strains that may not have had enough time to adapt to new disease pressures. The turbot is one of the most promising European aquaculture species. Furunculosis, caused by the bacterium Aeromonas salmonicida, produces important losses to turbot industry. An appealing solution is to achieve more robust broodstock, which can prevent or diminish the devastating effects of epizooties. Genomics strategies have been developed in turbot to look for candidate genes for resistance to furunculosis and a genetic map with appropriate density to screen for genomic associations has been also constructed. In the present study, a genome scan for QTL affecting resistance and survival to A. salmonicida in four turbot families was carried out. The objectives were to identify consistent QTL using different statistical approaches (linear regression and maximum likelihood) and to locate the tightest associated markers for their application in genetic breeding strategies.ResultsSignificant QTL for resistance were identified by the linear regression method in three linkage groups (LGs 4, 6 and 9) and for survival in two LGs (6 and 9). The maximum likelihood methodology identified QTL in three LGs (5, 6 and 9) for both traits. Significant association between disease traits and genotypes was detected for several markers, some of them explaining up to 17% of the phenotypic variance. We also identified candidate genes located in the detected QTL using data from previously mapped markers.ConclusionsSeveral regions controlling resistance to A. salmonicida in turbot have been detected. The observed concordance between different statistical methods at particular linkage groups gives consistency to our results. The detected associated markers could be useful for genetic breeding strategies. A finer mapping will be necessary at the detected QTL intervals to narrow associations and around the closely associated markers to look for candidate genes through comparative genomics or positional cloning strategies. The identification of associated variants at specific genes will be essential, together with the QTL associations detected in this study, for future marker assisted selection programs.

Optimal use of genetic markers in conservation programmes

Monte Carlo simulations were carried out in order to study the benefits of using molecular markers to minimize the homozygosity by descent in a conservation scheme of the Iberian pig. A selection criterion is introduced: the overall expected heterozygosity of the group of selected individuals. The method to implement this criterion depends on the type of information available. In the absence of molecular information breeding animals are chosen that minimize the average group coancestry calculated from pedigree. If complete molecular information is known the average group coancestry is calculated either from markers alone or by combining pedigree and genotypes with the markers. When a limited number of markers and alleles per marker are considered, the optimal criterion is the average group coancestry based on markers. Other alternatives, such as optimal within-family selection and frequency- dependent selection, are also analysed.

Using genome-wide information to minimize the loss of diversity in conservation programmes.

We study here the effect of using genome-wide marker data versus genealogical data in population management for the maintenance of diversity in conservation schemes using optimal contributions. We re-examine the benefits of using molecular data for different population and genome sizes and compare different management strategies according to the group of individuals where we take decisions (parents or offspring). We also study the consequences of using estimated genealogical coancestries calculated from molecular information. Using genome-wide marker data performed usually better than using genealogical data or estimated genealogical coancestry to maintain expected and observed heterozygosity. Furthermore, when we could take decisions acting on the offspring, a larger heterozygosity was maintained than when we based our decisions on the potential parents.

Using genomic tools to maintain diversity and fitness in conservation programmes

Conservation programmes aim at maximizing the survival probability of populations, by minimizing the loss of genetic diversity, which allows populations to adapt to changes, and controlling inbreeding increases. The best known strategy to achieve these goals is optimizing the contributions of the parents to minimize global coancestry in their offspring. Results on neutral scenarios showed that management based on molecular coancestry could maintain more diversity than management based on genealogical coancestry when a large number of markers were available. However, if the population has deleterious mutations, managing using optimal contributions can lead to a decrease in fitness, especially using molecular coancestry, because both beneficial and harmful alleles are maintained, compromising the long‐term viability of the population. We introduce here two strategies to avoid this problem: The first one uses molecular coancestry calculated removing markers with low minor allele frequencies, as they could be linked to selected loci. The second one uses a coancestry based on segments of identity by descent, which measures the proportion of genome segments shared by two individuals because of a common ancestor. We compare these strategies under two contrasting mutational models of fitness effects, one assuming many mutations of small effect and another with few mutations of large effect. Using markers at intermediate frequencies maintains a larger fitness than using all markers, but leads to maintaining less diversity. Using the segment‐based coancestry provides a compromise solution between maintaining diversity and fitness, especially when the population has some inbreeding load.

Enhancement of the Luminescent Properties of a New Red-Emitting Phosphor, Mn2(HPO3)F2, by Zn Substitution

The Mn(2)(HPO(3))F(2) phase has been synthesized as single crystals by using mild hydrothermal conditions. The compound crystallizes in the orthorhombic Pnma space group, with unit cell parameters of a = 7.5607(8), b = 10.2342(7), and c = 5.5156(4) Å, with Z = 4. The crystal structure consists of a three-dimensional framework formed by alternating (010) layers of [MnO(3)F(3)] octahedra linked up by three connected [HPO(3)] tetrahedra. Luminescence measurements were performed at different temperatures between 10 and 150 K. The 10 K emission spectrum of the octahedrally coordinated Mn(II) cation exhibits a broad band centered at around 615 nm corresponding to the (4)T(1) → (6)A(1) transition. In order to explore the effect of the Mn(II) concentration and the possibility of enhancing the luminescence properties of the Mn(II) cation in Mn(2)(HPO(3))F(2), different intermediate composition members of the finite solid solution with the general formula (Mn(x)Zn(1-x))(2)(HPO(3))F(2) were prepared and their luminescent properties studied. The magnetic and specific heat behavior of M(2)(HPO(3))F(2) (M = Mn, Fe) have also been investigated. The compounds exhibit a global antiferromagnetic ordering with a spin canting phenomenon detected at approximately 30 K. The specific heat measurements show sharp λ-type peaks at 29.7 and 33.5 K for manganese and iron compounds, respectively. The total magnetic entropy is consistent with spin S = 5/2 and S = 2 of Mn(II) and Fe(II) cations.

Stable organic radical stacked by in situ coordination to rare earth cations in MOF materials

With the correct choice of the solvothermal conditions, we have achieved the unprecedented in situ formation of the free radical form of the anthraquinone-1,5-disulfonate molecule, and its favorable organization. The semiquinone radicals are coordinated to rare-earth cations to produce a 2D framework with a very high charge mobility and electric conductivity through the π–π-interactions. The existence of AQDS3−˙ anion radicals is proven on the base of: i) the electrical neutrality: elemental analyses for the different lanthanide RPF-8 bulks, the maximum residual electron densities in the structure, rule out the existence of any other neutralizing ion, ii) the geometrical modifications in the antraquinone molecules, and iii) although less definitive, due to the low magnetic moment μ = 0.39 μB, the exhibited paramagnetism for the La (3+) with no unpaired electrons.

Purging deleterious mutations in conservation programmes: combining optimal contributions with inbred matings

Conservation programmes aim at minimising the loss of genetic diversity, which allows populations to adapt to potential environmental changes. This can be achieved by calculating how many offspring every individual should contribute to the next generation to minimise global coancestry. However, an undesired consequence of this strategy is that it maintains deleterious mutations, compromising the viability of the population. In order to avoid this, optimal contributions could be combined with inbred matings, to expose and eliminate recessive deleterious mutations by natural selection in a process known as purging. Although some populations that have undergone purging experienced reduced inbreeding depression, this effect is not consistent across species. Whether purging by inbred matings is efficient in conservation programmes depends on the balance between the loss of diversity, the initial decrease in fitness and the reduction in mutational load. Here we perform computer simulations to determine whether managing a population by combining optimal contributions with inbred matings improves its long-term viability while keeping reasonable levels of diversity. We compare the management based on genealogical information with management based on molecular data to calculate coancestries. In the scenarios analysed, inbred matings never led to higher fitness and usually maintained lower diversity than random or minimum coancestry matings. Replacing genealogical with molecular coancestry can maintain a larger genetic diversity but can also lead to a lower fitness. Our results are strongly dependent on the mutational model assumed for the trait under selection, the population size during management and the reproductive rate.

Maintaining genetic diversity using molecular coancestry: the effect of marker density and effective population size

BackgroundThe most efficient method to maintain genetic diversity in populations under conservation programmes is to optimize, for each potential parent, the number of offspring left to the next generation by minimizing the global coancestry. Coancestry is usually calculated from genealogical data but molecular markers can be used to replace genealogical coancestry with molecular coancestry. Recent studies showed that optimizing contributions based on coancestry calculated from a large number of SNP markers can maintain higher levels of diversity than optimizing contributions based on genealogical data. In this study, we investigated how SNP density and effective population size impact the use of molecular coancestry to maintain diversity.ResultsAt low SNP densities, the genetic diversity maintained using genealogical coancestry for optimization was higher than that maintained using molecular coancestry. The performance of molecular coancestry improved with increasing marker density, and, for the scenarios evaluated, it was as efficient as genealogical coancestry if SNP density reached at least 3 times the effective population size.However, increasing SNP density resulted in reduced returns in terms of maintained diversity. While a benefit of 12% was achieved when marker density increased from 10 to 100 SNP/Morgan, the benefit was only 2% when it increased from 100 to 500 SNP/Morgan.ConclusionsThe marker density of most SNP chips already available for farm animals is sufficient for molecular coancestry to outperform genealogical coancestry in conservation programmes aimed at maintaining genetic diversity. For the purpose of effectively maintaining genetic diversity, a marker density of around 500 SNPs/Morgan can be considered as the most cost effective density when developing SNP chips for new species. Since the costs to develop SNP chips are decreasing, chips with 500 SNPs/Morgan should become available in a short-term horizon for non domestic species.

Magnetic evolution of the antiferromagnetic Co2−xCux(OH)PO4 (0 ≤x≤ 2) solid solution. A neutron diffraction study

The Co2−xCux(OH)PO4 (0 ≤ x ≤ 2) solid solution was prepared from hydrothermal synthesis. Neutron powder diffraction patterns show that the Co2+ and Cu2+ ions are simultaneously present in both the [MO4(OH)2] octahedra and the [MO4(OH)] distorted trigonal bipyramid topologies. The evolution of the lattice parameters follows Vegard’s law in the whole range of substitution. This study allowed us to determine correctly the a and b crystallographic parameters of the Cu2(OH)PO4 phase which were interchanged in the literature. The magnetic behaviour in the cobalt–copper compounds indicates the existence of overall antiferromagnetic interactions as predominant. Three-dimensional magnetic ordering with critical temperatures of 69, 64, 60 and 47 K for x = 0.1, 0.3, 0.5 and 1 respectively is observed. The magnetic study of Co1.9Cu0.1(OH)PO4 suggests a spin-glass like state below 10 K. AC measurements obtained at different frequencies and applied fields confirm the freezing process in Co1.9Cu0.1 and the long range interactions in the Co2−xCux(OH)PO4 (x ≤ 1) phases. For x > 1, the magnetic dimensionality decreases with the increase of Cu(II) amount being of short range for x = 2. These results are attributed to the presence of the unpaired electron in the dx2−y2 orbital and the absence of overlap between neighbour ions. Specific-heat measurements confirm the evolution to a short range magnetic system with the Cu(II) amount. From low-temperature neutron diffraction data, it can be observed that the existence of antiferromagnetic order for x ≤ 1 is originated by the antiparallel ordering of both ferromagnetic linear octahedral chains and trigonal bipyramidal dimers. The propagation vector is k = [0,0,0] and the magnetic moments are aligned in the z direction. The values of the main magnetic exchange pathways [M–O–M] are characteristic of ferro- and antiferromagnetic couplings with a superexchange ferromagnetic angle, M(1)–O(3)–M(2) of 107–109°, which plays an important role in the competition of the freezing process. These results are explained on the basis of both the electronic configuration and the correlations between structural and magnetic properties.