Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Arsenic tolerance in Arabidopsis is mediated by two ABCC-type phytochelatin transporters

Arsenic is an extremely toxic metalloid causing serious health problems. In Southeast Asia, aquifers providing drinking and agricultural water for tens of millions of people are contaminated with arsenic. To reduce nutritional arsenic intake through the consumption of contaminated plants, identification of the mechanisms for arsenic accumulation and detoxification in plants is a prerequisite. Phytochelatins (PCs) are glutathione-derived peptides that chelate heavy metals and metalloids such as arsenic, thereby functioning as the first step in their detoxification. Plant vacuoles act as final detoxification stores for heavy metals and arsenic. The essential PC-metal(loid) transporters that sequester toxic metal(loid)s in plant vacuoles have long been sought but remain unidentified in plants. Here we show that in the absence of two ABCC-type transporters, AtABCC1 and AtABCC2, Arabidopsis thaliana is extremely sensitive to arsenic and arsenic-based herbicides. Heterologous expression of these ABCC transporters in phytochelatin-producing Saccharomyces cerevisiae enhanced arsenic tolerance and accumulation. Furthermore, membrane vesicles isolated from these yeasts exhibited a pronounced arsenite [As(III)]-PC(2) transport activity. Vacuoles isolated from atabcc1 atabcc2 double knockout plants exhibited a very low residual As(III)-PC(2) transport activity, and interestingly, less PC was produced in mutant plants when exposed to arsenic. Overexpression of AtPCS1 and AtABCC1 resulted in plants exhibiting increased arsenic tolerance. Our findings demonstrate that AtABCC1 and AtABCC2 are the long-sought and major vacuolar PC transporters. Modulation of vacuolar PC transporters in other plants may allow engineering of plants suited either for phytoremediation or reduced accumulation of arsenic in edible organs

Speciation and distribution of arsenic and localization of nutrients in rice grains

Arsenic (As) contamination of rice grains and the generally low concentration of micronutrients in rice have been recognized as a major concern for human health. Here, we investigated the speciation and localization of As and the distribution of (micro) nutrients in rice grains because these are key factors controlling bioavailability of nutrients and contaminants. Bulk total and speciation analyses using high-pressure liquid chromatography (HPLC)-inductively coupled plasma mass spectrometry (ICP-MS) and X-ray absorption near-edge spectroscopy (XANES) was complemented by spatially resolved microspectroscopic techniques (mu-XANES, mu-X-ray fluorescence (mu-XRF) and particle induced X-ray emission (PIXE)) to investigate both speciation and distribution of As and localization of nutrients in situ. The distribution of As and micronutrients varied between the various parts of the grains (husk, bran and endosperm) and was characterized by element-specific distribution patterns. The speciation of As in bran and endosperm was dominated by As(III)-thiol complexes. The results indicate that the translocation from the maternal to filial tissues may be a bottleneck for As accumulation in the grain. Strong similarities between the distribution of iron (Fe), manganese (Mn) and phosphorus (P) and between zinc (Zn) and sulphur (S) may be indicative of complexation mechanisms in rice grains

Arsenic phytoextraction and hyperaccumulation by fern species Fitoextração e hiperacumulação de arsênio por espécies de samambaias

Arsenic (As) is an ubiquitous trace metalloid found in all environmental media. Its presence at elevated concentrations in soils derives from both anthropogenic and natural inputs. Arsenic is a toxic and carcinogenic element, which has caused severe environmental and health problem worldwide. Technologies currently available for the remediation of arsenic-contaminated sites are expensive, environmentally disruptive, and potentially hazardous to workers. Phytoextraction, a strategy of phytoremediation, uses plants to clean up contaminated soils and has been successfully applied to arsenic contaminated soils. It has the advantage of being cost-effective and environmentally friendly. A major step towards the development of phytoextraction of arsenic-impacted soils is the discovery of the arsenic hyper accumulation in ferns, first in Pteris vittata, which presented an extraordinary capacity to accumulate 2.3% arsenic in its biomass. Another fern, Pityrogramma calomelanos was found to exhibit the same hyperaccumulating characteristics. After that, screening experiments have revealed that the Pteris genus is really unique in that many species have the potential to be used in phytoextraction of arsenic. In general, these plants seem to have both constitutive and adaptive mechanisms for accumulating or tolerating high arsenic concentration. In the past few years, much work has been done to understand and improve the hyperaccumulating capability of these amazing plants. In particular, the field of molecular biology seems to hold the key for the future of the phytoremediation.<br>O arsênio e um metalóide traço encontrado basicamente em todos os ambientes. Elevadas concentrações de arsênio no solo podem acontecer naturalmente devido ao intemperismo de rochas ricas em arsênio, como também de atividades antropogênicas. O arsênio é um elemento tóxico e cancerígeno. Em muitas partes do mundo, a contaminação pelo arsênio tem causado problemas ambientais e de saude. As técnicas disponíveis para a remediação do arsênio são economicamente proibitivas, destroem a paisagem natural e ainda podem afetar a saúde de pessoas diretamente envolvidas no processo. A fitoextração, uma das estratégias da fitoremediação, utiliza plantas para descontaminar solos e tem sido aplicada com sucesso em solos contaminados com arsênio e outros elementos. Dentre muitas vantagens, essa técnica tem baixo custo quando comparada com as convencionais. Um ponto chave no desenvolvimento da fitoextração foi a constatação de que samambaias hiperacumulam arsênio. Primeiro, em Pteris vittata, que apresentou extraordinária capacidade para remover arsênio do solo, concentrando 2.3% do arsênio na biomassa. Em seguida, foi observado que a samambaia Pityrogramma calomelanos possui capacidade semelhante para acumular arsênio. Essa característica peculiar foi observada em outras samambaias do genero Pteris. Em geral, essas plantas parecem apresentar mecanismos constitutivos e adaptativos que permitem elevada absorção e sobrevivência em solos com altas concentrações de arsênio. Muitas pesquisas têm sido conduzidas no sentido de entender e aumentar a capacidade de aborção de arsênio dessas plantas. Em particular, a chave para a aplicação bem sucedida da fitoremediação parece estar na biologia molecular