Descripción: Twenty-six isolates obtained from soybean crops (Glycine max) with typical anthracnose symptoms were identified as Colletotrichum truncatum (73 %) and C. destructivum (26 %). Their genetic relationships were studied using the AFLP method. A UPGMA phenogram divided the strains into two clusters corresponding with the two species. Genetic distances based on association coefficient were 0.71-0.89 among the 18 C. truncatum strains and 0.67-1 among the eight C. destructivum strains. Genetic variability within species, measured in terms of percentage of polymorphic loci, was high (<90%). Only two isolates showed 100% similarity, suggesting high intraspecific variability. © 2013. Mycotaxon, Ltd.

Descripción: Drosophila serido Vilela & Sene is a polytypic and cactophilic species with broad geographic distribution in Brazil. The morphology of the aedeagi of eight natural populations of D. serido was analyzed. Based on features of their aedeagi, populations of D. serido were discriminated with an efficiency of nearly 75%. The analysis using the Mantel test suggests that the morphological divergence of D. serido is correlated with the geographic distance among populations. There is no single cause to explain the observed pattern; therefore, the results were discussed considering the three main hypotheses to explain the aedeagus evolution: lock and key, pleiotropy and sexual selection. Alternatively, the aedeagus variability of D. serido might be related to environmental causes, such as temperature and/or host cacti.

Descripción: It is universally true in ecological communities, terrestrial or aquatic, temperate or tropical, that some species are very abundant, others are moderately common, and the majority are rare. Likewise, eukaryotic genomes also contain classes or "species" of genetic elements that vary greatly in abundance: DNA transposons, retrotransposons, satellite sequences, simple repeats and their less abundant functional sequences such as RNA or genes. Are the patterns of relative species abundance and diversity similar among ecological communities and genomes? Previous dynamical models of genomic diversity have focused on the selective forces shaping the abundance and diversity of transposable elements (TEs). However, ideally, models of genome dynamics should consider not only TEs, but also the diversity of all genetic classes or "species" populating eukaryotic genomes. Here, in an analysis of the diversity and abundance of genetic elements in >500 eukaryotic chromosomes, we show that the patterns are consistent with a neutral hypothesis of genome assembly in virtually all chromosomes tested. The distributions of relative abundance of genetic elements are quite precisely predicted by the dynamics of an ecological model for which the principle of functional equivalence is the main assumption. We hypothesize that at large temporal scales an overarching neutral or nearly neutral process governs the evolution of abundance and diversity of genetic elements in eukaryotic genomes. © 2013 Serra et al.

Descripción: Many grasshopper species are considered of agronomical importance because they cause damage to pastures and crops. Comprehension of pest population dynamics requires a clear understanding of the genetic diversity and spatial structure of populations. In this study we report on patterns of genetic variation in the South American grasshopper Dichroplus elongatus which is an agricultural pest of crops and forage grasses of great economic significance in Argentina. We use Direct Amplification of Minisatellite Regions (DAMD) and partial sequences of the cytochrome oxydase 1 (COI) mitochondrial gene to investigate intraspecific structure, demographic history and gene flow patterns in twenty Argentinean populations of this species belonging to different geographic and biogeographic regions. DAMD data suggest that, although genetic drift and migration occur within and between populations, measurable relatedness among neighbouring populations declines with distance and dispersal over distances greater than 200 km is not typical, whereas effective gene flow may occur for populations separated by less than 100 km. Landscape analysis was useful to detect genetic discontinuities associated with environmental heterogeneity reflecting the changing agroecosystem. The COI results indicate the existence of strong genetic differentiation between two groups of populations located at both margins of the Paraná River which became separated during climate oscillations of the Middle Pleistocene, suggesting a significant restriction in effective dispersion mediated by females and large scale geographic differentiation. The number of migrants between populations estimated through mitochondrial and DAMD markers suggest that gene flow is low prompting a non-homogeneous spatial structure and justifying the variation through space. Moreover, the genetic analysis of both markers allows us to conclude that males appear to disperse more than females, reducing the chance of the genetic loss associated with recent anthropogenic fragmentation of the D. elongatus studied range. © 2012 Rosetti, Remis.

Descripción: Phytophthora sojae causes root and stem rot, one of the most important diseases of soybean worldwide. Genetic diversity of 32 Phytophthora sojae isolates of different geographic origin from Argentina was evaluated with RAPD markers. The isolates were collected from diseased soybean plants and soil samples from Santa Fe, Buenos Aires, Córdoba and Entre Ríos provinces, in the Pampeana Region. DNA was amplified with 20 decanucleotides primers. Seven primers amplified 49 fragments, of which 35 were polymorphic, indicating high variability. RAPD analysis detected intraspecific variability even among isolates of the same geographic origin. © 2007 by The Mycological Society of America.

Descripción: In addition to their role in DNA repair, recombination events are associated with processes aimed at providing the genetic variability needed for adaptation and evolution of a population. In bacteria, recombination is involved in the appearance of new variants by allowing the incorporation of exogenous DNA or the reshuffling of endogenous sequences. Here we show that HpMutS2, a protein belonging to the MutS2 family in Helicobacter pylori, is not involved in mismatch repair but inhibits homologous and homeologous recombination. Disruption of HpmutS2 leads to an increased efficiency of exogenous DNA incorporation. HpMutS2 has a selective affinity for DNA structures mimicking recombination intermediates with no specificity for homoduplex DNA or mismatches. The purified protein has an ATPase activity stimulated by the same DNA structures. Finally, we show that HpMutS2 inhibits DNA strand exchange reactions in vitro. Thus, MutS2 proteins are candidates for controlling recombination and therefore genetic diversity in bacteria.

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: Background. The rapid evolution of genital morphology is a fascinating feature that accompanies many speciation events. However, the underlying patterns and explanatory processes remain to be settled. In this work we investigate the patterns of intraspecific variation and interspecific divergence in male genitalic morphology (size and shape) in the cactophilic sibling species Drosophila buzzatii and D. koepferae. Genital morphology in interspecific hybrids was examined and compared to the corresponding parental lines. Results. Despite of being siblings, D. buzzatii and D. koepferae showed contrasting patterns of genital morphological variation. Though genitalic size and shape variation have a significant genetic component in both species, shape varied across host cacti only in D. buzzatii. Such plastic expression of genital shape is the first evidence of the effect of rearing substrate on genitalic morphology in Drosophila. Hybrid genital morphology was not intermediate between parental species and the morphological resemblance to parental strains was cross-dependent. Conclusion. Our results suggest the evolution of different developmental networks after interspecific divergence and the existence of a complex genetic architecture, involving genetic factors with major effects affecting genital morphology. © 2007 Soto et al; licensee BioMed Central Ltd.

Descripción: Populations may adapt in response to selection pressures imposed by global environmental change. In marine zooplankton, measurements of the heritability of key life history characters, and thus the potential for evolution, are still rare. Here we demonstrate the feasibility of conducting controlled mating experiments with the dioecious appendicularian Oikopleura dioica to explore the narrow-sense heritability and genetic correlation among morphological and life history traits. At our standard laboratory conditions (15 ± 1°C, 100 μg C l-1), mature females were larger (1.213 ± 0.19 mm, mean ± SD) and lived longer (8.5 ± 2.18 d) than did males (1.115 ± 0.15 mm, 7.6 ± 2.07 d). The heritability (±SE) of morphological characters was low (trunk size, 0.37 ± 0.25; house size, 0.39 ± 0.23) to moderate (tail length, 0.50 ± 0.31). In contrast, an important life history trait, lifespan, showed high heritability (0.89 ± 0.47) and may therefore respond rapidly to selection pressure, either in the laboratory or in the wild. © Inter-Research 2011.

Descripción: Background: Functional genetic markers have important implications for genetic analysis by providing direct estimation of functional diversity. Although high throughput sequencing techniques for functional diversity analysis are being developed nowadays, the use of already well established variable markers present in candidate genes is still an interesting alternative for mapping purposes and functional diversity studies. SSR markers are routinely used in most plant and animal breeding programs for many species including Eucalyptus. SSR markers derived from candidate genes (SSR-CG) can be used effectively in co-segregation studies and marker-assisted diversity management. Results: In the present study, eight new non reported SSRs were identified in seven candidate genes for wood properties in Eucalyptus globulus: cinnamoyl CoA reductase (CCR), homocysteine S-methyltransferase (HMT), shikimate kinase (SK), xyloglucan endotransglycosylase 2 (XTH2), cellulose synthase 3 (CesA3), glutathione S-transferase (GST) and the transcription factor LIM1. Microsatellites were located in promoters, introns and exons, being most of them CT dinucleotide repeats. Genetic diversity of these eight CG-derived SSR-markers was explored in 54 unrelated genotypes. Except for XTH2, high levels of polymorphism were detected: 93 alleles (mean of 13.1 sd 1.6 alleles per locus), a mean effective number of alleles (Ne) of 5.4 (sd 1.6), polymorphic information content values (PIC) from 0.617 to 0.855 and probability of Identity (PI) ranging from 0.030 to 0.151. Conclusions: This is the first report on the identification, characterization and diversity analysis of microsatellite markers located inside wood quality candidate genes (CG) from Eucalyptus globulus. This set of markers is then appropriate for characterizing genetic variation, with potential usefulness for quantitative trait loci (QTL) mapping in different eucalypts genetic pedigrees and other applications such as fingerprinting and marker assisted diversity management. © 2012 by Pontificia Universidad Católica de Valparaíso, Chile.

Descripción: Understanding the genetic architecture of any quantitative trait requires identifying the genes involved in its expression in different environmental conditions. This goal can be achieved by mutagenesis screens in genetically tractable model organisms such as Drosophila melanogaster. Temperature during ontogenesis is an important environmental factor affecting development and phenotypic variation in holometabolous insects. In spite of the importance of phenotypic plasticity and genotype by environment interaction (GEI) for fitness related traits, its genetic basis has remained elusive. In this context, we analyzed five different adult morphological traits (face width, head width, thorax length, wing size and wing shape) in 42 co-isogenic single P-element insertional lines of Drosophila melanogaster raised at 17°C and 25°C. Our analyses showed that all lines differed from the control for at least one trait in males or females at either temperature. However, no line showed those differences for all traits in both sexes and temperatures simultaneously. In this sense, the most pleiotropic candidate genes were CG34460, Lsd-2 and Spn. Our analyses also revealed extensive genetic variation for all the characters mostly indicated by strong GEIs. Further, our results indicate that GEIs were predominantly explained by changes in ranking order in all cases suggesting that a moderate number of genes are involved in the expression of each character at both temperatures. Most lines displayed a plastic response for at least one trait in either sex. In this regard, P-element insertions affecting plasticity of a large number of traits were associated to the candidate genes Btk29A, CG43340, Drak and jim. Further studies will help to elucidate the relevance of these genes on the morphogenesis of different body structures in natural populations of D. melanogaster. © 2013 Carreira et al.

Descripción: Developmental time and body size are two positively correlated traits closely related to fitness in many organisms including Drosophila. Previous work suggested that these two traits are involved in a trade-off that may result from a negative genetic correlation between their effects on pre-adult and adult fitness. Here, we examine the evolution of developmental time and body size (indexed by wing length) under artificial Selection applied to one or both traits in replicated D. buzzatii populations. Directional changes in both developmental time and wing length indicate the presence of substantial additive genetic variance for both traits. The strongest response to selection for fast development was found in lines selected simultaneously to reduce both developmental time and wing length, probably as an expected consequence of a synergistic effect of indirect selection. When selection was applied in the direction opposite to the putative genetic correlation, that is, large wing length but fast development, no responses were observed for developmental time. Lines selected to reduce both wing length and developmental time diverged slightly faster from the control than lines selected to increase wing length and reduce developmental time. However, wing length did not diverge from the control in lines selected only for fast development. These results suggest a complex genetic basis of the correlation between developmental time and wing length, but are generally consistent with the hypothesis that both traits are related in a trade-off. However, we found that this trade-off may disappear under uncrowded conditions, with fast-developing lines exhibiting a higher pre-adult viability than other lines when tested at high larval density.

Descripción: Nucleotide variation was studied in a 1.1 kb section of the coding region of an Esterase gene (Est-A) that maps in the center of the segments rearranged by polymorphic inversions in the cactophilic Drosophila buzzatii. We examine 30 homozygous second-chromosome lines differing in gene arrangement and three D. koepferae isofemale lines as outgroups. Our data show that Est-A is a highly polymorphic gene at both synonymous and replacement sites. Significant departures from homogeneity in the distribution of the ratio of silent polymorphism to divergence predicted by the neutral theory reveals a local excess of silent polymorphism. This is consistent with the presence of two apparent narrow peaks of elevated silent polymorphism surrounding nonconservative amino acid substitutions. These polymorphisms as well as others at synonymous and nonsynonymous sites are shared with D. koepferae. We suggest that the presence of shared nucleotide polymorphisms is probably due to interspecific gene flow and/or balancing selection acting on replacement variants and/or to a decreased probability of loss of ancestral polymorphisms caused by linkage to an adaptive inversion polymorphism. Recurrent mutation and persistence of neutral ancestral polymorphisms cannot, however, be ruled out. The analysis of the distribution of nucleotide variation among the three chromosomal arrangements sampled reveals that derived arrangements (J and JZ3) are less polymorphic than the ancestral ST, and that the widely distributed ST and J arrangements are genetically differentiated. However, a significant number of polymorphisms are shared between arrangements, suggesting frequent exchange either from gene conversion or from double crossovers in heterokaryotypes. Finally, our present results in combination with data of sequence variation at the breakpoints of inversion J suggest that this old gene arrangement has risen in frequency in relatively recent times.

Descripción: Haemalopinus suis (Anoplura) and Menacanthus stramineus (Mallophaga) have been cytogenetically analyzed. Both species have 2n = 10, holokinetic chromosomes, and achiasmatic male meiosis. Bivalents orientate with their long axis perpendicular to the spindle fibers at melaphase I, and first anaphase is reductional. As in other species of Phthiraptera, male gametogenesis follows a particular pattern: each cell entering meiosis results in a cyst of 64 (in H. suis) and 32 (in M. stramineus) spermatozoa and 64/32 non‐functional cells (=pycnotic nuclei). The results are compared with those previously reported for Phthiraptera, and a new terminology for the different stages of male gametogenesis is proposed. The low chromosome number together with the achiasmatic nature of male meiosis and the mitotic divisions that follow meiosis may restrict the potential for genetic variability. This might be related to the high host specificity of these parasites. Copyright © 1993, Wiley Blackwell. All rights reserved

Descripción: Insertion of factor MudJ in the intergenic region between divergent genes yrfF and yrfE, at centisome 76 in the genome of Salmonella enterica serovar Typhimurium LT2, confers the characteristics recently described for mucM mutants, i.e. mucoidy and resistance to mecillinam. Cloning of the intergenic region plus either the yrfF or the yrfE gene in a multicopy plasmid showed that only the plasmid carrying the yrfF gene complemented mucM mutants, thus suggesting that mucM mutations are in fact yrfF mutations. A null yrfF mutation obtained by insertion of a kanamycin cassette into the yrfF open reading frame (yrfF28::Kan) produced abortive colonies when transduced to a wild-type strain but was normally accepted by rcsB, rcsC or yojN strains. Neither mutations preventing synthesis of the capsular exopolysaccharide colanic acid (cps, galE) nor rcsA mutations, which reduce expression of cps genes, conferred tolerance to the lethal yrfF28::Kan mutation. Spontaneous suppressor mutations arose very frequently in abortive yrfF28::Kan colonies, and all of them affected either rcsC, yojN, or rcsB genes. Thus, the lethal effect caused by inactivation of gene yrfF appears to be mediated by a function that is dependent on the rcsC-yojN-rcsB phosphorelay system but does not involve synthesis of colanic acid. © 2003 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.

Descripción: Background. Understanding the genetic architecture of ecologically relevant adaptive traits requires the contribution of developmental and evolutionary biology. The time to reach the age of reproduction is a complex life history trait commonly known as developmental time. In particular, in holometabolous insects that occupy ephemeral habitats, like fruit flies, the impact of developmental time on fitness is further exaggerated. The present work is one of the first systematic studies of the genetic basis of developmental time, in which we also evaluate the impact of environmental variation on the expression of the trait. Results. We analyzed 179 co-isogenic single P[GT1]-element insertion lines of Drosophila melanogaster to identify novel genes affecting developmental time in flies reared at 25°C. Sixty percent of the lines showed a heterochronic phenotype, suggesting that a large number of genes affect this trait. Mutant lines for the genes Merlin and Karl showed the most extreme phenotypes exhibiting a developmental time reduction and increase, respectively, of over 2 days and 4 days relative to the control (a co-isogenic P-element insertion free line). In addition, a subset of 42 lines selected at random from the initial set of 179 lines was screened at 17°C. Interestingly, the gene-by-environment interaction accounted for 52% of total phenotypic variance. Plastic reaction norms were found for a large number of developmental time candidate genes. Conclusion. We identified components of several integrated time-dependent pathways affecting egg-to-adult developmental time in Drosophila. At the same time, we also show that many heterochronic phenotypes may arise from changes in genes involved in several developmental mechanisms that do not explicitly control the timing of specific events. We also demonstrate that many developmental time genes have pleiotropic effects on several adult traits and that the action of most of them is sensitive to temperature during development. Taken together, our results stress the need to take into account the effect of environmental variation and the dynamics of gene interactions on the genetic architecture of this complex life-history trait. © 2008 Mensch et al; licensee BioMed Central Ltd.

Descripción: Subclinical low-grade systemic inflammation has been associated with obesity, insulin resistance and metabolic syndrome (MS). Recent studies have highlighted the role of gut microbiota in these disorders. The toll-like receptor 4 (TLR4) plays a key role in the innate immune response activation. We studied two polymorphisms (+3725G/C and 11350G/C) in the 3′ untranslated region (3′UTR) of the TLR4 gene that may alter its expression and their association with metabolic disorders related to systemic inflammation. We cloned the 3′UTR into a luciferase reporter system and compared wild-type 3′UTR (WT) and +3725C variant (MUT) constructs luciferase activities. MUT construct reduced the reporter gene activity by 30% compared to WT (P = 0.0001). To evaluate the association between these polymorphisms with biochemical and clinical overweight related variables, we conducted a population cross-sectional study in 966 men of Argentine general population. Considering smoking as a confounding variable that causes systemic inflammation, we studied these possible effects in both, smokers and nonsmokers. The 11350G/C polymorphism was not detected in our sample whereas the CC genotype of +3725 polymorphism was associated with lean subjects (p = 0.011) and higher Adiponectin levels (p = 0.021). Subjects without any NCEP/ATP III MS component were associated with this genotype as well (p = 0.001). These results were strengthened in nonsmokers, in which CC genotype was associated with lean subjects (p = 0.003) and compared with G carriers showed significantly lower BMI (25.53 vs. 28.60 kg/m2; p = 0.023) and waist circumference (89.27 vs. 97.51 cm; p = 0.025). None of these associations were found in smokers. These results showed that +3725C variant has a functional effect down-regulating gene expression and it could be considered as a predictive factor against overweight, particularly in nonsmokers. Considering the role of TLR4 in inflammation, these findings would suggest that the presence of +3725C variant could predict a lower prevalence of chronic metabolic disorders. © 2012 Penas-Steinhardt et al.

Descripción: To gain insights into the natural variation of root hydraulics and its molecular components, genotypic differences related to root water transport and plasma membrane intrinsic protein (PIP) aquaporin expression were investigated in 13 natural accessions of Arabidopsis (Arabidopsis thaliana). The hydraulic conductivity of excised root systems (Lpr) showed a 2-fold variation among accessions. The contribution of aquaporins to water uptake was characterized using as inhibitors mercury, propionic acid, and azide. The aquaporin-dependent and -independent paths of water transport made variable contributions to the total hydraulic conductivity in the different accessions. The distinct suberization patterns observed among accessions were not correlated with their root hydraulic properties. Real-time reverse transcription-polymerase chain reaction revealed, by contrast, a positive overall correlation between Lpr and certain highly expressed PIP transcripts. Root hydraulic responses to salt stress were characterized in a subset of five accessions (Bulhary-1, Catania-1, Columbia-0, Dijon-M, and Monte-Tosso-0 [Mr-0]). Lpr was down-regulated in all accessions except Mr-0. In Mr-0 and Catania-1, cortical cell hydraulic conductivity was unresponsive to salt, whereas it was down-regulated in the three other accessions. By contrast, the five accessions showed qualitatively similar aquaporin transcriptional profiles in response to salt. The overall work provides clues on how hydraulic regulation allows plant adaptation to salt stress. It also shows that a wide range of root hydraulic profiles, as previously reported in various species, can be observed in a single model species. This work paves the way for a quantitative genetics analysis of root hydraulics. © 2011 American Society of Plant Biologists.