Evolution of Helix Formation in the Ribosomal Internal Transcribed Spacer 2 (ITS2) and Its Significance for RNA Secondary Structures

Helices are the most common elements of RNA secondary structure. Despite intensive investigations of various types of RNAs, the evolutionary history of the formation of new helices (novel helical structures) remains largely elusive. Here, by studying the nuclear ribosomal Internal Transcribed Spacer 2 (ITS2), a fast-evolving part of the eukaryotic nuclear ribosomal operon, we identify two possible types of helix formation: one type is “dichotomous helix formation”—transition from one large helix to two smaller helices by invagination of the apical part of a helix, which significantly changes the shape of the original secondary structure but does not increase its complexity (i.e., the total length of the RNA). An alternative type is “lateral helix formation”—origin of an extra helical region by the extension of a bulge loop or a spacer in a multi-helix loop of the original helix, which does not disrupt the pre-existing structure but increases RNA size. Moreover, we present examples from the RNA sequence literature indicating that both types of helix formation may have implications for RNA evolution beyond ITS2.     

Resistance to pathogens in terpene down-regulated orange fruits inversely correlates with the accumulation of D-limonene in peel oil glands

Volatile organic compounds (VOCs) are secondary metabolites acting as a language for the communication of plants with the environment. In orange fruits, the monoterpene D-limonene accumulates at very high levels in oil glands from the peel. Drastic down-regulation of D-limonene synthase gene expression in the peel of transgenic oranges harboring a D-limonene synthase transgene in antisense (AS) configuration altered the monoterpene profile in oil glands, mainly resulting in reduced accumulation of D-limonene. This led to fruit resistance against Penicillium digitatum (Pd), Xanthomonas citri subsp. citri (Xcc) and other specialized pathogens. Here, we analyze resistance to pathogens in independent AS and empty vector (EV) lines, which have low, medium or high D-limonene concentrations and show that the level of resistance is inversely related to the accumulation of D-limonene in orange peels, thus explaining the need of high D-limonene accumulation in mature oranges in nature for the efficient attraction of specialized microorganism frugivores.     

Docking and molecular dynamics studies of peripheral site ligand–oximes as reactivators of sarin-inhibited human acetylcholinesterase

In the present work, we performed docking and molecular dynamics simulations studies on two groups of long-tailored oximes designed as peripheral site binders of acetylcholinesterase (AChE) and potential penetrators on the blood brain barrier. Our studies permitted to determine how the tails anchor in the peripheral site of sarin-inhibited human AChE, and which aminoacids are important to their stabilization. Also the energy values obtained in the docking studies corroborated quite well with the experimental results obtained before for these oximes.     

Lifestyle and Ice: The Relationship between Ecological Specialization and Response to Pleistocene Climate Change

Major climatic changes in the Pleistocene had significant effects on marine organisms and the environments in which they lived. The presence of divergent patterns of demographic history even among phylogenetically closely-related species sharing climatic changes raises questions as to the respective influence of species-specific traits on population structure. In this work we tested whether the lifestyle of Antarctic notothenioid benthic and pelagic fish species from the Southern Ocean influenced the concerted population response to Pleistocene climatic fluctuations. This was done by a comparative analysis of sequence variation at the cyt b and S7 loci in nine newly sequenced and four re-analysed species. We found that all species underwent more or less intensive changes in population size but we also found consistent differences between demographic histories of pelagic and benthic species. Contemporary pelagic populations are significantly more genetically diverse and bear traces of older demographic expansions than less diverse benthic species that show evidence of more recent population expansions. Our findings suggest that the lifestyles of different species have strong influences on their responses to the same environmental events. Our data, in conjunction with previous studies showing a constant diversification tempo of these species during the Pleistocene, support the hypothesis that Pleistocene glaciations had a smaller effect on pelagic species than on benthic species whose survival may have relied upon ephemeral refugia in shallow shelf waters. These findings suggest that the interaction between lifestyle and environmental changes should be considered in genetic analyses.     

Seroepidemiological study of human hydatidosis and trichinosis, with the indirect hemagglutination reaction, in San Juan de la Costa County. Osorno, X Region, Chile. 1990-1991]

San Juan de la Costa County (40 degrees 45' South lat., 73 degrees 19' West long.) is located in the Osorno province, South of Chile. Its population is 8,486 inhabitants. The basic economic activities are agriculture, cattle raising, timber production and manufacture of wood and coal. According to official reports, the incidence of human hydatidosis and trichinosis in this locality in 1989 were 24 and 59 per 100,000 respectively. In order to contribute to a better knowledge of the epidemiology of human hydatidosis and trichinosis in San Juan de la Costa County, an indirect hemagglutination test (IHAT) for these parasitoses was performed to 511 randomized people. Nine (1.8%) individuals resulted positive for hydatidosis and twenty four (4.7%) were positive for trichinosis. Some considerations on the corresponding prophylactic measures are proposed.     

The interaction of decorin core protein fragments with type I collagen.

To further define the molecular interaction between decorin and type I collagen we generated a 20 kD fragment containing the N-terminal half of the core protein by Endoproteinase Arg C digestion and a 40 kD fragment including all leucine-rich repeats in the central part of decorin core by cleavage with 2-nitro-5-thiocyanobenzoate. The fragments did not influence collagen fibril formation, even at high concentration, and radioactive fragments showed little binding to collagen fibrils. Our observations suggest that neither the N-terminal half nor the central leucine-rich repeats of the decorin core protein can, by itself, interact fully with fibrillar collagen.     

Induction of adventitious buds on the cotyledons ofAbies concolor x Abies grandis hybrid seedlings

Possibilities of adventitious buds induction on the cotyledons obtained from sterile seedlings ofAbies concolor xAbies grandis hybrid were investigated. The following variables influencing bud induction and their further development were studied: the effect of expiant age, the effect of different growth regulators and their concentrations and duration of their application. The most suitable expiants proved to be the cotyledons of 7 d old seedlings. The most efficient cytokinin was benzylaminopurine (S mg l^?1) in combination with napthaleneacetic acid (0.01 mg l^?1). The most optimal duration of treatment was 17 to 21 d culture of explants on induction medium. Shoot growth was achieved on basal medium to which 14 mg 1^?1 spermidine was added.