Holocentric Chromosomes of Luzula elegans Are Characterized by a Longitudinal Centromere Groove, Chromosome Bending, and a Terminal Nucleolus Organizer Region

The structure of holocentric chromosomes was analyzed in mitotic cells of Luzula elegans. Light and scanning electron microscopy observations provided evidence for the existence of a longitudinal groove along each sister chromatid. The centromere-specific histone H3 variant, CENH3, colocalized with this groove and with microtubule attachment sites. The terminal chromosomal regions were CENH3-negative. During metaphase to anaphase transition, L. elegans chromosomes typically curved to a sickle-like shape, a process that is likely to be influenced by the pulling forces of microtubules along the holocentric axis towards the corresponding microtubule organizing regions. A single pair of 45S rDNA sites, situated distal to Arabidopsis-telomere repeats, was observed at the terminal region of one chromosome pair. We suggest that the 45S rDNA position in distal centromere-free regions could be required to ensure chromosome stability. Copyright (C) 2011 S. Karger AG, Base

Water quality in a small catchment of Piracicaba River, SP

A microbacia do Ribeirão dos Marins, fluente do Rio Piracicaba, é importante ao município de Piracicaba, São Paulo, haja vista que concentra a maior área de produção de hortaliças, as quais são irrigadas com as águas do ribeirão. Com o objetivo de avaliar a qualidade da água, coletaram-se amostras de fevereiro a dezembro de 2005 em sete pontos ao longo do ribeirão, considerando-se o uso e ocupação do solo. As variáveis de qualidade de água analisadas foram: físicas e químicas: sedimentos em suspensão, pH, condutividade elétrica, alcalinidade, turbidez, potássio, cálcio, magnésio, cobre, ferro, manganês, zinco, sódio, fósforo, sulfato, cloreto, nitrogênio amoniacal e nitrato. As análises foram realizadas no Laboratório de Ecologia do Instituto de Estudos Florestais e no Laboratório de Água do Departamento de Engenharia Rural, ambos pertencentes à ESALQ-USP. Os resultados obtidos foram comparados com a Resolução nº 357 de 17 março de 2005, do Conselho Nacional de Meio Ambiente (CONAMA) que estabelece a classificação das águas brasileiras. As águas do ribeirão dos Marins apresentaram-se fora do padrão estabelecido pela Resolução 357/2005 do CONAMA, para a irrigação de hortaliças._________________________________________________________________________________________ ABSTRACT: The Marins creek watershed is important to the Piracicaba municipal district because it concentrates a large area of horticultural production, which is irrigated with the creek water. With the aim to evaluate the water quality, samples were collected from February to December 2005 at seven points along the creek according to land use. The parameters of quality analyzed were physical and chemical: suspended sediments, pH, electrical conductivity, alkalinity, turbidity, potassium, calcium, magnesium, copper, iron, manganese, zinc, sodium, phosphorus, sulfate, chloride, ammonia nitrogen, and nitrate. The analyses were made at the Ecology Laboratory of Forest Studies Institute and Water Laboratory at the Rural Engineering Department, both belonging to the Escola Superior de Agricultura “Luiz de Queiroz”, Universidade de São Paulo. The results were compared with the Brazilian legislation (Resolution nº 357 of March 17, 2005 of National Concil of Environment) which establishes the Brazilian water classification. The Marins water did not meet the limits established by the Brazilian legislation to irrigate the horticultural productio

Integrative genetic map of repetitive DNA in the sole Solea senegalensis genome shows a Rex transposon located in a proto-sex chromosome

Repetitive sequences play an essential role in the structural and functional evolution of the genome, particularly in the sexual chromosomes. The Senegalese sole (Solea senegalensis) is a valuable flatfish in aquaculture albeit few studies have addressed the mapping and characterization of repetitive DNA families. Here we analyzed the Simple Sequence Repeats (SSRs) and Transposable elements (TEs) content from fifty-seven BAC clones (spanning 7.9 Mb) of this species, located in chromosomes by multiple fluorescence in situ hybridization (m-BAC-FISH) technique. The SSR analysis revealed an average density of 675.1 loci per Mb and a high abundance (59.69%) of dinucleotide coverage was observed, being 'AC' the most abundant. An SSR-FISH analysis using eleven probes was also carried out and seven of the 11 probes yielded positive signals. 'AC' probes were present as large clusters in almost all chromosomes, supporting the bioinformatic analysis. Regarding TEs, DNA transposons (Class II) were the most abundant. In Class I, LINE elements were the most abundant and the hAT family was the most represented in Class II. Rex/Babar subfamily, observed in two BAC clones mapping to chromosome pair 1, showed the longest match. This chromosome pair has been recently reported as a putative sexual proto-chromosome in this species, highlighting the possible role of the Rex element in the evolution of this chromosome. In the Rex1 phylogenetic tree, the Senegalese sole Rex1 retrotransposon could be associated with one of the four major ancient lineages in fish genomes, in which it is included O. latipes