Descripción: Biological invasions are excellent opportunities to study the evolutionary forces leading to the adaptation of a species to a new habitat. Knowledge of the introduction history of colonizing species helps tracking colonizing routes and assists in defining management strategies for invasive species. The Palearctic species Drosophila subobscura is a good model organism for tracking colonizations since it was detected in Chile and western North America three decades ago and later on in the Atlantic coast of Argentina. To unravel the origin of the Argentinean colonizers two populations have been analysed with several genetic markers. Chromosomal arrangements and microsatellite alleles found in Argentina are almost similar to those observed in Chile and USA. The lethal allelism test demonstrates that the lethal gene associated with the O5 inversions in Argentina is identical to that found in Chile and USA, strongly supporting the hypothesis that all the American colonizing populations originated from the same colonization event. A secondary bottleneck is detected in the Argentinean populations and the genetic markers suggest that these populations originated from the invasion of 80-150 founding individuals from Chile. © 2008 European Society For Evolutionary Biology.

Descripción: The inversion polymorphism of the cactophilic fly Drosophila buzzatii was studied in two natural populations. We assessed the temporal changes and microspatial population structure. We observed a significant increase in the frequency of arrangement 2J at the expense of 2ST in both populations. These gene arrangements appear to affect the life-history of flies differently. Environmental heterogeneity explains the karyotype coexistence in nature. The analysis of population structure showed that differentiation of inversion frequencies among individual breeding sites, the rotting clacodes of Opuntia vulgaris, was highly significant. The karyotypic frequencies did not depart significantly from Hardy-Weinberg expectations, neither in individual rots nor in the total population. These results suggest that the observed population structure can be easily accounted by random genetic drift.

Descripción: Odour-guided behaviour is a quantitative trait determined by many genes that are sensitive to gene-environment interactions. Different natural populations are likely to experience different selection pressures on the genetic underpinnings of chemosensory behaviour. However, few studies have reported comparisons of the quantitative genetic basis of olfactory behaviour in geographically distinct populations. We generated isofemale lines of Drosophila melanogaster from six populations in Argentina and measured larval and adult responses to benzaldehyde. There was significant variation within populations for both larval and adult olfactory behaviour and a significant genotype × sex interaction (GSI) for adult olfactory behaviour. However, there is substantial variation in the contribution of GSI to the total phenotypic variance among populations. Estimates of evolvability are orders of magnitude higher for larvae than for adults. Our results suggest that the potential for evolutionary adaptation to the chemosensory environment is greater at the larval feeding stage than at the adult reproductive stage. © 2008 The Authors.

Descripción: Trimerotropis pallidipennis is an American grasshopper whose South American populations are polymorphic for pericentric inversions. Colonization of southern latitudes was by North American grasshoppers with basic chromosome arrangements, presumably along the Andean dry lands of South America. In Argentina, the frequencies of some of the rearrangements are correlated with geographical and climatic variables, following similar patterns among different ecological gradients, and are probably maintained by geographically variable coefficients of selection. Restriction site variation of mitochondrial DNA is used as a tool for determining the species history in relation to the formation of clines. Populations located along an altitudinal gradient, and others outside the cline, are analysed through phylogeographical studies. There is no strong geographical orientation in the unrooted tree connecting all 17 mitochondrial DNA haplotypes found. Many of them are present in most of the populations analysed, indicating high gene flow. The fact that there is no obvious differentiation in haplotype distribution between both extremes of the cline nor between chromosomally differentiated populations shows that the cline is not the result of a hybrid zone and reinforces the selection hypothesis. The estimation of the overall nucleotide divergence between the hypothetical ancestral haplotype and the other molecules shows that T. pallidipennis haplotypes started diverging from each other about 3 Myr ago. This result is in agreement with the time when the Isthmus of Panama rose (2-3 Myr ago), probably favouring the migration of many species between both hemispheres.

Descripción: Grasshoppers have been much less studied than Drosophila when it comes to inversion polymorphisms, despite the occurrence of this rearrangement in several species of grasshoppers. In the present study, 354 males from a natural population of the New World species Trimerotropis pallidipennis, polymorphic for 6 pericentric inversions in 4 chromosome pairs, were sampled at the beginning and at the end of the adult life span. This sampling, along with the fact that generations in this grasshopper are annual and discrete, was done to detect differential adult male longevity among karyotypes and departures from formal null models, such as gametic phase equilibrium. These methods allow the detection of natural selection taking place in the wild. The comparison between age classes showed that some inversions were significantly more frequent in one sample, thus revealing the operation of natural selection. Gametic phase disequilibrium was detected in the sample of aged males but not in the sample of young ones. Furthermore, here we aim to detect the phenotypic targets of longevity selection by examining morphometric characters, in order to have a clearer idea of the relation between inversions and natural selection in this species. These results corroborate previous studies that suggested that the inversions are involved in natural selection, and an adaptive model has been proposed for the pattern of inversion frequencies throughout several populations at different altitudes and latitudes.

Descripción: Second chromosome inversion and genotypic frequencies at seven allozyme loci, differentially associated with inversions, were determined in seven natural populations of Drosophila buzzatii. The patterns of variation of allozymes and the inversion polymorphisms were significantly different, indicating the role of adaptive differentiation for the latter. Moreover, the patterns of population structure varied among allozyme loci, suggesting the operation of diversifying selection for certain loci. Differentiation was negligible for Leucyl-amino peptidase (Lap) and Peptidase-2 (Pep-2), low to moderate for Aldehyde oxidase (Aldox), Peptidase-1 (Pep-1) and Esterase-1 (Est-1) and high for Esterase-2 (Est-2) and Xanthine dehydrogenase (Xdh). Significant linkage disequilibria were detected between inversions and Aldox, Est-1, Est-2 and Xdh. Multiple regression analyses of inversion and allele frequencies on environmental variables revealed the existence of clines for inversions, Est-1, Est-2, Xdh and Aldox along altitudinal, latitudinal and/or climatic gradients. Tests using conditional allele frequencies showed that Est-1 and Aldox clines could be accounted for by hitchhiking with inversions, whereas natural selection should be invoked to explain the clines observed for Est-2 and Xdh.

Descripción: Previous works in a colonized and an original population of Drosophila buzzatii have shown a consistent relationship between the inversion polymorphism and thorax length, a measure of body size. However, the populations studied in those reports share a close genealogical relationship as suggested by several lines of evidence. In the present paper, we revisit this issue by analysing the correlation between second chromosome arrangements and thorax length in two Argentinian natural populations (Termas de Rio Hondo and Arroyo Escobar) from different biogeographic areas with different host plants. Our findings are: (1) inversion frequencies were significantly different between populations; (2) the mean thorax length of flies collected in both populations was not significantly different; and (3) we obtain confirming evidence that flies carrying 2st, the ancestral gene order, have on average a smaller body size than those carrying the derived arrangements (2j and 2jz3). These results suggest that the biometrical effect of inversions on body size previously described are due to genetic differences between arrangements and not to the close historical relationship between the populations studied in previous reports.

Descripción: DNA size polymorphisms were utilized in a study of 24 natural populations of Ceratitis capitata Wiedemann (Diptera: Tephritidae) from Argentina. The first intron of alcohol dehydrogenase 1 gene (Adh1) was amplified using exon priming intron crossing-polymerase chain reaction. Three size variants were detected among the 307 samples analyzed. To better differentiate the size variants, further digestion of PCR products with the EcoRI restriction enzyme was carried out. Complete nucleotide sequences of the three-allele variants were obtained and single changes, insertions, deletions, and EcoRI recognition sites were located. Population allele frequencies were analyzed and a global mean heterozygosity (He) of 0.33 was obtained. In most populations, observed allelic frequencies conformed to Hardy-Weinberg expectations. Significant differences between provinces and sampling sites within these provinces, and among some populations were found. The average number of insects exchanged among populations (Nm) was estimated and high values were observed between Argentina and populations from two African countries (Morocco and Kenya), Australia, and Hawaii (Kauai). Pest introduction sources and dispersion patterns in Argentina are discussed based on these results as well as on available bibliographical data. © 2010 The Authors. Journal compilation © 2010 The Netherlands Entomological Society.

Descripción: Clinal analysis for fitness-related traits provides a well-known approach to investigate adaptive evolution. Several fitness-related traits (developmental time, thorax length, wing length and wing loading) were measured at two laboratory generations (G7 and G33) of D. buzzatii from an altitudinal gradient from northwestern Argentina, where significant thermal differences persist. Developmental time (DT) was positively correlated with altitude of origin of population. Further, DT was negatively correlated with maximal mean temperature at the site of origin of population, and this thermal variable decreases with altitude. Wing loading tended to be larger in highland than in lowland populations, suggesting that flight performance is subject to stronger selection pressure in highland populations. Developmental time showed a significant increase with laboratory generation number. There was no significant correlation between developmental time and body size across populations along the altitudinal cline of DT. This result illustrates that developmental time and body size do not always evolve in the same direction, even though both traits are often positively and genetically correlated in a well-known tradeoff in Drosophila.

Descripción: The porphyrias are a group of inherited metabolic disorders of heme biosynthesis which result from a partial deficiency in one of its seven specific enzymes, after its first and rate limiting enzyme, delta-aminolevulinic acid synthetase. They can be classified on the basis of their clinical manifestations into cutaneous, acute and mixed disorders. Acute intermittent porphyria (AIP) is the most common type of hepatic acute porphyrias, inherited as an autosomal dominant trait, caused by a defect in the gene which codifies for the heme enzyme porphobilinogen deaminase. Its prevalence in the Argentinean population is about 1:125,000. A partial deficiency in another enzyme, protoporphyrinogen oxidase, produces variegate porphyria (VP), the second acute porphyria most frequent in the Argentinean population (1:600,000). Here, we review all the mutations we have found in 46 AIP and 9 VP unrelated Argentinean patients. To screen for mutations in symptomatic patients, we have proposed a geneticresearch strategy.

Descripción: The section Algarobia of genus Prosopis involves important natural resources in arid and semiarid regions of the world. Their rationale use requires a better knowledge of their biology, genetics and mating system. There are contradictory information about their mating system. Some authors claim they are protogynous and obligate outcrosser. However, some evidence have been shown indicating that they might not be protogynous and that they might be somewhat self-fertile. The current paper analyses genetic structure and mating system parameters in populations of seven species of this section from South and North America based on isozyme data. In all species a significant homozygote excess was found in the offspring population but not in mother plant genotypes. Multilocus and mean single locus outcrossing rates (tm, ts) indicated that about 15 % selfing can occur in the studied populations. The heterogeneity between pollen and ovule allele frequencies was low suggesting population structuration, in agreement with the estimates of correlation of tm within progeny (rt) and correlation of outcrossed paternity (rp). The difference of F(IS) estimates between offspring and mother plants suggest some selection favouring heterozygotes between seedling and adult stages.

Descripción: The inversion polymorphisms of the cactophilic Drosophila buzzatti Patterson and Wheeler (Diptera: Drosophilidae) were studied in new areas of its distribution in Argentina. A total of thirty-eight natural populations, including 29 from previous studies, were analyzed using multiple regression analyses. The results showed that about 23% of total variation was accounted for by a multiple regression model in which only altitude contributed significantly to population variation, despite the fact that latitude and longitude were also included in the model. Also, inversion frequencies exhibited significant associations with mean annual temperature, precipitation, and atmospheric pressure. In addition, expected heterozygosity exhibited a negative association with temperature and precipitation and a positive association with atmospheric pressure. The close similarity of the patterns detected in this larger dataset to previous reports is an indication of the stability of the clines. Also, the concurrence of the clines detected in Argentina with those reported for colonizing populations of Australia suggests the involvement of natural selection as the main mechanism shaping inversion frequencies in D. buzzatii.

Descripción: The karyotype of Baccharis coridifolia DC., a dioecious diploid species consists of 16 chromosomes with median (m) and 2 with submedian centromeric positions (sm) (2n = 18). Meiotic analyses of 219 male plants belonging to 12 populations showed across a wide geographical range one quadrivalent and seven bivalents in all of them. The quadrivalent involves the four biggest m chromosomes and probably constitutes a sex multivalent carrying in tight linkage the sex genes and provides a mechanism whereby permanent translocation heterozygosity is maintained. In metaphase I alternate orientation of the quadrivalent was predominant (85.71 %). Fourteen megaspore mother cells were analyzed and did not show the quadrivalent. A model for the origin and maintenance of the sexual translocation system is presented. It is assumed that there are two non-allelic factors M and n; M would be a dominant female suppresor and n a recessive male-suppresor. The excess of male plants observed in several populations at different localities might result from heterotic effects of some gene complexes carried by the translocation. This excess probably ensures a good supply of pollen for the vagaries of insect pollination at flowering time.

Descripción: Background: Prosopis alba (Fabaceae) is an important native tree adapted to arid and semiarid regions of north-western Argentina which is of great value as multipurpose species. Despite its importance, the genomic resources currently available for the entire Prosopis genus are still limited. Here we describe the development of a leaf transcriptome and the identification of new molecular markers that could support functional genetic studies in natural and domesticated populations of this genus.Results: Next generation DNA pyrosequencing technology applied to P. alba transcripts produced a total of 1,103,231 raw reads with an average length of 421 bp. De novo assembling generated a set of 15,814 isotigs and 71,101 non-assembled sequences (singletons) with an average of 991 bp and 288 bp respectively. A total of 39,000 unique singletons were identified after clustering natural and artificial duplicates from pyrosequencing reads.Regarding the non-redundant sequences or unigenes, 22,095 out of 54,814 were successfully annotated with Gene Ontology terms. Moreover, simple sequence repeats (SSRs) and single nucleotide polymorphisms (SNPs) were searched, resulting in 5,992 and 6,236 markers, respectively, throughout the genome. For the validation of the the predicted SSR markers, a subset of 87 SSRs selected through functional annotation evidence was successfully amplified from six DNA samples of seedlings. From this analysis, 11 of these 87 SSRs were identified as polymorphic. Additionally, another set of 123 nuclear polymorphic SSRs were determined in silico, of which 50% have the probability of being effectively polymorphic.Conclusions: This study generated a successful global analysis of the P. alba leaf transcriptome after bioinformatic and wet laboratory validations of RNA-Seq data.The limited set of molecular markers currently available will be significantly increased with the thousands of new markers that were identified in this study. This information will strongly contribute to genomics resources for P. alba functional analysis and genetics. Finally, it will also potentially contribute to the development of population-based genome studies in the genera. © 2013 Torales et al.; licensee BioMed Central Ltd.

Descripción: Background. Association analysis is a powerful tool to identify gene loci that may contribute to phenotypic variation. This includes the estimation of nucleotide diversity, the assessment of linkage disequilibrium structure (LD) and the evaluation of selection processes. Trait mapping by allele association requires a high-density map, which could be obtained by the addition of Single Nucleotide Polymorphisms (SNPs) and short insertion and/or deletions (indels) to SSR and AFLP genetic maps. Nucleotide diversity analysis of randomly selected candidate regions is a promising approach for the success of association analysis and fine mapping in the sunflower genome. Moreover, knowledge of the distance over which LD persists, in agronomically meaningful sunflower accessions, is important to establish the density of markers and the experimental design for association analysis. Results. A set of 28 candidate genes related to biotic and abiotic stresses were studied in 19 sunflower inbred lines. A total of 14,348 bp of sequence alignment was analyzed per individual. In average, 1 SNP was found per 69 nucleotides and 38 indels were identified in the complete data set. The mean nucleotide polymorphism was moderate ( = 0.0056), as expected for inbred materials. The number of haplotypes per region ranged from 1 to 9 (mean = 3.54 1.88). Model-based population structure analysis allowed detection of admixed individuals within the set of accessions examined. Two putative gene pools were identified (G1 and G2), with a large proportion of the inbred lines being assigned to one of them (G1). Consistent with the absence of population sub-structuring, LD for G1 decayed more rapidly (r 2= 0.48 at 643 bp; trend line, pooled data) than the LD trend line for the entire set of 19 individuals (r2= 0.64 for the same distance). Conclusion. Knowledge about the patterns of diversity and the genetic relationships between breeding materials could be an invaluable aid in crop improvement strategies. The relatively high frequency of SNPs within the elite inbred lines studied here, along with the predicted extent of LD over distances of 100 kbp (r2∼0.1) suggest that high resolution association mapping in sunflower could be achieved with marker densities lower than those usually reported in the literature.

Descripción: Background: Human papillomavirus (HPV) is the main causative agent of cervical cancer, particularly high risk strains such us HPV-16, -18 and -31. The viral encoded E2 protein acts as a transcriptional modulator and exerts a key role in viral DNA replication. Thus, E2 constitutes an attractive target for developing antiviral agents. E2 is a homodimeric protein that interacts with the DNA target through an α-helix of each monomer. However, a peptide corresponding to the DNA recognition helix of HPV-16 E2 binds DNA with lower affinity than its full-length DNA binding domain. Therefore, in an attempt to promote the DNA binding of the isolated peptide, we have designed a conjugate compound of the E2 α-helix peptide and a derivative of the antibiotic distamycin, which involves simultaneous minor- and major-groove interactions. Methodology/Principal Findings: An E2 α-helix peptide-distamycin conjugate was designed and synthesized. It was characterized by NMR and CD spectroscopy, and its DNA binding properties were investigated by CD, DNA melting and gel shift experiments. The coupling of E2 peptide with distamycin does not affect its structural properties. The conjugate improves significantly the affinity of the peptide for specific DNA. In addition, stoichiometric amounts of specific DNA increase meaningfully the helical population of the peptide. The conjugate enhances the DNA binding constant 50-fold, maintaining its specificity. Conclusions/Significance: These results demonstrate that peptide-distamycin conjugates are a promising tool to obtain compounds that bind the E2 target DNA-sequences with remarkable affinity and suggest that a bipartite major/minor groove binding scaffold can be a useful approach for therapeutic treatment of HPV infection. © 2011 Wetzler et al.

Descripción: Background: Freshwater lymnaeid snails can act as the intermediate hosts for trematode parasites such as the liver fluke Fasciola hepatica, that cause significant economic and biomedical burden worldwide, particularly through bovine fascioliasis. Transmission potential is tightly coupled to local compatibility with snail hosts, so accurate identification of lymnaeid species is crucial for understanding disease risk, especially when invasive species are encountered. Mendoza Province, in Argentina, is a center of livestock production and also an area of endemic fascioliasis transmission. However, the distribution of lymnaeid species in the region is not well known. Methods. This study examined lymnaeid snails from seven localities in the Department of Malarguë, Mendoza Province, using morphological and molecular analyses and also describing ecological variables associated with snail presence. Results: While morphological characters identified two species of lymnaeid, Galba truncatula and G. viatrix, molecular data revealed a third, cryptic species, G. neotropica, which was sympatric with G. viatrix. G. truncatula was exclusively found in high altitude (>1900 meters above sea level [masl]) sites, whereas mixed G. neotropica/G. viatrix localities were at middle elevations (1300-1900 masl), and G. viatrix was found alone at the lowest altitude sites (<1300 masl). Phylogenetic analysis using two mitochondrial markers revealed G. neotropica and G. viatrix to be closely related, and given their morphological similarities, their validities as separate taxonomic entities should be questioned. Conclusions: This study highlights the need of a robust taxonomic framework for the identification of lymnaeid snails, incorporating molecular, morphological and ecological variables while avoiding nomenclature redundancy. As the three species observed here, including one alien invasive species, are considered hosts of varying susceptibility to Fasciola parasites, and given the economic importance of fascioliasis for livestock production, this research has critical importance for the ultimate aim of controlling disease transmission. © 2013 Standley et al.; licensee BioMed Central Ltd.

Descripción: Variation in genome size of 24 populations belonging to 11 NW Patagonian species of Berberis was analysed as a function of the environment and geographical location. The variation showed three levels of discontinuity, two of which corresponded to diploid species (2n = 28) while the third corresponded to polyploid species (2n = 56). Diploids with DNA content ranging from 1.463 pg to 1.857 pg included Berberis cabrerae, B. chillanensis, B. montana, B. serrato-dentata and B. bidentata. Diploids with DNA content ranging from 2.875 pg to 3.806 pg included B. linearifolia, B. darwinii, B. parodii and B. empetrifolia. The genome size of the polyploid species B. buxifolia and B. heterophylla ranged from 5.809 pg to 6.844 pg. Principal component analysis (PCA) was applied to represent the variability of environmental conditions. The eigenvectors of the principal component axes showed that PCl discriminates the populations according to rainfall, types of vegetation and geomorphology; altitude and latitude, on the other hand, contribute to PC2 and PC3, respectively. From these results it is concluded: (1) that diploids with lower DNA content grow in high-elevation sites having greater rainfall but lower water availability; (2) diploids with higher DNA content are associated with half-elevation forests where the vegetative period is longer, the water availability is greater and the temperatures are higher; and (3) the distribution pattern of polyploids is considerably wider than that of diploids, which are geographically and ecologically restricted to forest areas. These results suggest that the C-value plays an important role in the ability of the species to adapt to different growing conditions. (C) 2000 Annals of Botany Company.