Dissociation of single-stranded DNA from nucleosomes following modification with acetic anhydride

Modification with acetic anhydride of nucleosomes from chicken erythrocytes at low ionic strength (less than 0.1 M NaCl) is accompanied by the formation of residual particles and the release of free DNA. This DNA has been identified as single-stranded by thermal denaturation, digestion with nuclease S1, and elution from hydroxyapatite. In contrast, if modification takes place at 0.6 M NaCl, the liberated DNA is mainly double-stranded. The release of the free energy stored in folded nucleosomal DNA, triggered by the weakening of lysine-DNA interactions which takes place upon modification, might be responsible for the observed denaturation of DNA at low ionic stregth.This work was supported in part by the Fondo de Investigaciones Sanitarias and Comisión Asesora de Investigación Científica y Técnica (Spain).Peer Reviewe

Dissociation of nucleosomal particles by chemical modification. Equivalence of the two binding sites for H2A.H2B dimers

3 páginas, 3 figuras.Treatment of nucleosomal particles with dimethylmaleic anhydride, a reagent for protein amino groups, is accompanied by a biphasic release of histones H2A plus H2B; one H2A.H2B dimer is more easily released than the other. This behavior allows the preparation of nucleosomal particles containing only one H2A.H2B dimer, which were complemented with 125I-labeled H2A.H2B. These reconstituted particles, which contain one labeled and one unlabeled H2A.H2B dimer, were treated with the amount of reagent needed to release one of the two H2A.H2B dimers. Radioactivity was equally distributed between residual particles and released proteins, which is consistent with equivalent binding sites in the nucleosomal particle for H2A.H2B dimers, rather than with intrinsically different sites. The asymmetric release of H2A.H2B dimers would be caused by a change in the binding site of one dimer following the release of the other. This behavior might be related to the structural dynamics of nucleosomes.This work was supported in part by the Fondo de Investigaciones Sanitarias and the Comisión Asesora de Investigacion Cientifica y Tecnica (Spain). The costs of publication of this article were defrayed in part by the payment of page charges.Peer reviewe

Adaptive signifi cance of the prolonged diapause in the western Mediterranean lycaenid butterfl y Tomares ballus (Lepidoptera: Lycaenidae)

Diapause is a common dormancy strategy exhibited by many species of invertebrates and insects to temporarily avoid seasonally recurring unfavourable conditions for their development, most usually in winter. Less frequently, a prolonged diapause lasting two or more years is described in species living in unpredictable environments where it is adaptive, but with signifi cant costs. In this paper we examine the occurrence of prolonged diapause in the lycaenid butterfl y Tomares ballus. Pupae of this species undergo an obligate diapause from mid-May to late January the following year. However, during our rearing experiments (from 2009 to 2016) the emergence of adults occurred sequentially and a fraction of the pupae remained in diapause for up to seven years. The annual percentage emergence after the fi rst year of diapause was 45.6%, and only barely exceeded 50.0% in 2015. Remarkably, 12 pupae (11.4% of the initial brood) remained in diapause in their eighth year. The negative exponential equation fi tted to the emergence data suggests that further emergences may occur within the next fi ve years. Therefore, the potential for successful prolonged diapause of T. ballus pupae may be more than 10 years. The adaptive value of this strategy is discussed in relation to the effects of adverse and unpredictable weather during the fl ight period of the butterfl y, intra-guild competition, parasitoids and changes in habitat quality. We suggest that this strategy may also be exhibited by other species of Mediterranean lycaenid

Novos rumos do direito civil

info:eu-repo/semantics/publishedVersio

Isolation of 91 polymorphic microsatellite loci in the western mediterranean endemic carex helodes (Cyperaceae)

Premise of the study: Microsatellite primers were developed for Carex helodes (Cyperaceae), a western Mediterranean endemic that is locally distributed in southern Portugal and southwestern Spain and rare in northern Morocco. Methods and Results: One hundred nine nuclear microsatellite markers were developed using a shotgun pyrosequencing method, resulting in 91 polymorphic and 18 monomorphic loci when tested using 19 individuals sampled from five populations from Portugal, Spain, and Morocco. Loci averaged 3.23 alleles per locus (SD = 1.15). In a single population (Cortelha population, Portugal), the 34 most polymorphic loci showed a mean observed heterozygosity of 0.357 (SD = 0.292) and mean expected heterozygosity of 0.384 (SD = 0.255). Conclusions: Next-generation sequencing allowed us to develop a high number of genetic markers with levels of polymorphism adequate to study gene flow among populations. However, when genotyping the individuals within a population, we found low levels of variation

L'acquisto a non domino

Recensão de: Mengoni, Luigi - L'acquisto a non domino. - Milán : Vita e pensiero, 1949. - 290 p.info:eu-repo/semantics/publishedVersio

The HaDREB2 transcription factor enhances basal thermotolerance and longevity of seeds through functional interaction with HaHSFA9

<p>Abstract</p> <p>Background</p> <p>Transcription factor HaDREB2 was identified in sunflower (<it>Helianthus annuus </it>L.) as a drought-responsive element-binding factor 2 (DREB2) with unique properties. HaDREB2 and the sunflower Heat Shock Factor A9 (HaHSFA9) co-activated the <it>Hahsp17.6G1 </it>promoter in sunflower embryos. Both factors could be involved in transcriptional co-activation of additional small heat stress protein (sHSP) promoters, and thus contribute to the HaHSFA9-mediated enhancement of longevity and basal thermotolerance of seeds.</p> <p>Results</p> <p>We found that overexpression of HaDREB2 in seeds did not enhance longevity. This was deduced from assays of basal thermotolerance and controlled seed-deterioration, which were performed with transgenic tobacco. Furthermore, the constitutive overexpression of HaDREB2 did not increase thermotolerance in seedlings or result in the accumulation of HSPs at normal growth temperatures. In contrast, when HaDREB2 and HaHSFA9 were conjointly overexpressed in seeds, we observed positive effects on seed longevity, beyond those observed with overexpression of HaHSFA9 alone. Such additional effects are accompanied by a subtle enhancement of the accumulation of subsets of sHSPs belonging to the CI and CII cytosolic classes.</p> <p>Conclusion</p> <p>Our results reveal the functional interdependency of HaDREB2 and HaHSFA9 in seeds. HaDREB2 differs from other previously characterized DREB2 factors in plants in terms of its unique functional interaction with the seed-specific HaHSFA9 factor. No functional interaction between HaDREB2 and HaHSFA9 was observed when both factors were conjointly overexpressed in vegetative tissues. We therefore suggest that additional, seed-specific factors, or protein modifications, could be required for the functional interaction between HaDREB2 and HaHSFA9.</p

Demographic limitation processes

20 páginas, 2 figuras, 1 tabla, 3 cuadros.-- Editor: Valladares, F.[ES]: Procesos de limitación demográfica. Este capítulo ofrece una revisión de los factores que afectan a la regeneración natural de la vegetación, considerando la serie de etapas demográficas que determinan la dinámica demográfica de una pobla- ción. Son muy escasos los estudios disponibles que analizan toda la serie de eventos concatenados entre la producción de flores y frutos y el establecimiento exitoso de una planta adulta reproductiva. También son escasos los trabajos que permiten establecer los efectos aplazados que tienen las interacciones con animales a lo largo del ciclo de regeneración. La aproximación que proponemos cuantifica las pérdidas de propágulos en cada etapa demográfica e identifica “cuellos de botella” del reclutamiento que pue- den colapsar la regeneración natural de una especie. Revisamos una serie de casos de estudio que ilustran diversos procesos de limitación demográfica. El uso de técnicas explícitamente demográficas es fundamental para comprender la evolución de las especies forestales Mediterráneas y para diseñar actuaciones de preservación de sus poblaciones y de su extraordinaria diversidad.[EN]: We review the main factors influencing recruitment limitation in Mediterranean woody species by considering the sequential stages that determine the demographic cycle. Very few studies examine the whole set of demographic stages, from flower production to the successful establishment of adult reproductive plants, and their influence on recruitment. There are also few studies exploring the delayed effects of animal interactions throughout the regeneration cycle, but the information on stage-specific effects is more detailed. We propose an approach that quantifies the propagule losses at each sequential demographic stage and identifies demographic bottlenecks that might collapse population growth. We review a series of case studies illustrating different limitation processes. The use of explicit demographic techniques is central to understand the evolution of Mediterranean woody species and to design sound, ecologically-based, conservation plans to preserve their extraordinary diversity.Juan Arroyo agradece la financiación otorgada a los proyectos 4474-91 (National Geographic Society), PB 91-0894, PB95-0551, 1FD97-0743-CO3-03, PB98-1144, BOS200307924-CO2-01 (MECD, MCyT). Los trabajos de Pedro Jordano han sido financiados con proyectos MECD y MCyT (1FD97-0743-CO3-01, PB 96-0857, BOS2000-1366-C02-01 y REN2003-00273), así como la Junta de Andalucía (PAI). Juan Luis García-Castaño estuvo financiado durante su período pre-doctoral con una beca FPU, AP96-27318040. El trabajo de Fernando Pulido ha sido parcialmente financiado por una beca FPI de la Junta de Extremadura y los proyectos regional IPR-0A050 y estatal BOS2002- 12222-E del Ministerio de Ciencia y Tecnología. Los trabajos de Patricio García-Fayos han sido financiados con proyectos MCyT (1FD97-0551), de la Generalitat Valenciana (02-046) y de la Institució Alfons el Magnánim (02-046)Peer reviewe