Descripción: Fil:Poggio, L. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Descripción: Even though substantial progress has been made to elucidate the physiological and environmental factors underpinning differences in body size, little is known about its genetic architecture. Furthermore, all animal species bear a specific relationship between the size of each organ and overall body size, so different body size traits should be investigated as well as their sexual dimorphism that may have an important impact on the evolution of body size. We have surveyed 191 co-isogenic lines of Drosophila melanogaster, each one of them homozygous for a single P-element insertion, and assessed the effects of mutations on different body size traits compared to the P-element-free co-isogenic control. Nearly 60% of the lines showed significant differences with respect to the control for these traits in one or both sexes and almost 35% showed trait- and sex-specific effects. Candidate gene mutations frequently increased body size in males and decreased it in females. Among the 92 genes identified, most are involved in development and/or metabolic processes and their molecular functions principally include protein-binding and nucleic acid-binding activities. Although several genes showed pleiotropic effects in relation to body size, few of them were involved in the expression of all traits in one or both sexes. These genes seem to be important for different aspects related to the general functioning of the organism. In general, our results indicate that the genetic architecture of body size traits involves a large fraction of the genome and is largely sex and trait specific. © 2009 Macmillan Publishers Limited All rights reserved.

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.

Descripción: By using improved pulsed field gel electrophoresis conditions, the molecular karyotype of the reference clone CL Brener selected for Trypanosoma cruzi genome project was established. A total of 20 uniform chromosomal bands ranging in size from 0.45 to 3.5 Megabase pairs (Mbp) were resolved in a single run. The weighted sum of the chromosomal bands was approximately 87 Mbp. Chromoblots were hybridized with 39 different homologous probes, 13 of which identified single chromosomes. Several markers showed linkage and four different linkage groups were identified, each comprising two markers. Densitometric analysis suggests that most of the chromosomal bands contain two or more chromosomes representing either homologous chromosomes and/or heterologous chromosomes with similar sizes.

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: The haploid DNA content of Aeshna confusa (2n = 27, n = 13 + XO, male). A. bonariensis (2n = 26, n = 12 + neo-XY, male) and A. cornigera planaltica (2n = 16, n = 7 + neo-XY, male) has been determined (2.16 ± 0.16 pg, 1.81 ± 0.17 pg, and 2.08 ± 0.08 pg, respectively). Despite the differences in chromosome size and number, differences in DNA content between species are not significant. The karyotypic analysis of Aeshna species leads to the conclusion that fusions between autosomes or autosome and the sex chromosome, are the only chromosome rearrangement that occurred during evolution. In the species here studied, fusions have taken place with a minimal loss of DNA; however, other species of the genus show important differences in genome size, which cannot only be justified by fusion events.

Descripción: This paper presents the karyotype and DNA content of 12 diploid species of Hippeastrum from South America. The variation in genome size is compared with the karyotype and DNA content of Amaryllis belladonna from South Africa. The Hippeastrum species present a uniform and bimodal basic karyotype formula, but significant differences are found in the total chromosome volume (TCV) and nuclear DNA content. A positive correlation between the DNA content and TCV is also observed. The karyotype's constancy is a product of changes in DNA content occurring in the whole chromosome complement. The DNA addition to the long and short sets of chromosomes varies independently. In species with higher DNA contents, the short chromosomes add equal DNA amounts to both arms, maintaining their metacentric morphology, whereas the long chromosomes add DNA only to the short arm, increasing the chromosome symmetry. These data show that the evolutionary changes in DNA amount are proportional to chromosome length, maintaining the karyotypic uniformity. A. belladonna has a larger DNA content and possesses a karyotype different from that of Hippeastrum spp., supporting the distinction between the two genera and upholding the name Amaryllis for the South African entity against Hippeastrum for the South American genus. © 2007 The Linnean Society of London.

Descripción: Removal of the poly(A) tail is the first step in the degradation of many eukaryotic mRNAs. In metazoans and yeast, the Ccr4/Caf1/Not complex has the predominant deadenylase activity, while the Pan2/Pan3 complex may trim poly(A) tails to the correct size, or initiate deadenylation. In trypanosomes, turnover of several constitutively-expressed or long-lived mRNAs is not affected by depletion of the 5'-3' exoribonuclease XRNA, but is almost completely inhibited by depletion of the deadenylase CAF1. In contrast, two highly unstable mRNAs, encoding EP procyclin and a phosphoglycerate kinase, PGKB, accumulate when XRNA levels are reduced. We here show that degradation of EP mRNA was partially inhibited after CAF1 depletion. RNAi-targeting trypanosome PAN2 had a mild effect on global deadenylation, and on degradation of a few mRNAs including EP. By amplifying and sequencing degradation intermediates, we demonstrated that a reduction in XRNA had no effect on degradation of a stable mRNA encoding a ribosomal protein, but caused accumulation of EP mRNA fragments that had lost substantial portions of the 5' and 3' ends. The results support a model in which trypanosome mRNAs can be degraded by at least two different, partially independent, cytoplasmic degradation pathways attacking both ends of the mRNA. © 2009 The Author(s).

Descripción: Twenty-one native populations (1120 individuals) of maize from Northern Argentina were studied. These populations, which belong to 13 native races were cultivated at different altitudes (80-3620 m). Nineteen of the populations analyzed showed B chromosome (Bs) numerical, polymorphism. The frequency of individuals with Bs varied from 0 to 94%. The number of Bs per plant varied from 0 to 8 Bs, with the predominant doses being 0, 1, 2, and 3. Those populations with varying number of Bs showed a positive and statistically significant correlation of mean number of Bs with altitude. The DNA content, in plants without Bs (A-DNA)(2n = 20), of 17 populations of the 21 studied was determined. A 36% variation (5.0-6.8 pg) in A-DNA content was found. A significant negative correlation between A-DNA content and altitude of cultivation and between A-DNA content and mean number of Bs was found. This indicates that there is a close interrelationship between the DNA content of A chromosomes and doses of Bs. These results suggest that there is a maximum limit to the mass of nuclear DNA so that Bs are tolerated as long as this maximum limit is not exceeded.

Descripción: We studied hantavirus seroprevalence and virus variability in rodent populations in Diego Gaynor, northwest of Buenos Aires province, Argentina. Rodent samplings were conducted in railroads and cropfield borders in March and July 1999, September and December 2000, and March 2001. Antibody detection was performed by an enzyme link immunosorbent assay (ELISA), using the recombinant nucleoprotein of Andes (AND) virus as antigen. Tissue samples were taken from positive antibody individuals in order to confirm the presence of hantavirus genomic material and to identify virus genotypes. Akodon azarae was the most abundant species, followed by Oligoryzomys flavescens, while Calomys laucha and C. musculinus were rarely caught. We found a rate of seroprevalence of 9.3% for a total sample of 291 A. azarae and 13.5% for 37 O. flavescens. After molecular analyses of hantavirus, we confirmed the presence of hantavirus genomic material in 16 individuals with ELISA (+) results and two individuals with ELISA (-). Four amplimers for each species were sequenced and compared to the corresponding sequences of representative hantaviruses. We identified the AND Cent Lee from three O. flavescens, and the Pergamino virus from four A. azarae and from one O. flavescens. A. azarae males had higher seroprevalence than females, and heavier individuals showed higher seroprevalence than lighter ones. We did not find seroprevalence differences according to sex in O. flavescens, although this result may have been produced by the low sample size. The lowest seroprevalence was found in a period of high rodent density, when juveniles prevailed in the population. We found higher seroprevalences than those detected in previous studies for other localities of central Argentina where cases of hantavirus pulmonary syndrome (HPS) have been reported. The presence of AND Cent Lee virus in rodent populations of the study area, which is responsible of HPS cases in central Argentina, suggests that human populations are at risk of HPS disease, although there were not reported cases of this disease until today.