Hyperaccumulation of arsenic in the shoots of Arabidopsis silenced for arsenate reductase (ACR2)

Endogenous plant arsenate reductase (ACR) activity converts arsenate to arsenite in roots, immobilizing arsenic below ground. By blocking this activity, we hoped to construct plants that would mobilize more arsenate aboveground. We have identified a single gene in the Arabidopsis thaliana genome, ACR2, with moderate sequence homology to yeast arsenate reductase. Expression of ACR2 cDNA in Escherichia coli complemented the arsenate-resistant and arsenate-sensitive phenotypes of various bacterial ars operon mutants. RNA interference reduced ACR2 protein expression in Arabidopsis to as low as 2% of wild-type levels. The various knockdown plant lines were more sensitive to high concentrations of arsenate, but not arsenite, than wild type. The knockdown lines accumulated 10- to 16-fold more arsenic in shoots (350–500 ppm) and retained less arsenic in roots than wild type, when grown on arsenate medium with <8 ppm arsenic. Reducing expression of ACR2 homologs in tree, shrub, and grass species should play a vital role in the phytoremediation of environmental arsenic contamination

Uma tecnologia com múltiplas aplicações A technology with multiple applications

O melhoramento vegetal vem sendo praticado pelo homem há milhares de anos. Entretanto, esse processo de domesticação tornou os vegetais mais susceptíveis a pragas e doenças. O melhoramento clássico permitiu, por cruzamento, a manipulação genética dos vegetais com conseqüente aumento na produtividade agrícola. Recentemente, a tecnologia do DNA recombinante ampliou as possibilidades de integração de genes exógenos ao genoma vegetal, resultando na produção das plantas transgênicas. Apesar das grandes discussões em torno do assunto, essas plantas representam hoje um caminho promissor para o melhoramento vegetal. Inúmeros exemplos de estratégias de transferência de genes conferiram, com sucesso, resistência a herbicidas, vírus, fungos, bactérias e insetos ou produziram um aumento na qualidade dos alimentos. Além das aplicações biotecnológicas, as plantas transgênicas têm contribuído significativamente para o estudo do funcionamento dos genes, tais como a análise da regulação da expressão gênica e o estudo das funções das proteínas codificadas pelos diferentes genes da planta.<br>Plant breeding has been a human practice for some thousands of years. However, this process of domestication has made plants more vulnerable to pests and diseases. Classical plant breeding has allowed the genetic manipulation of plants through crossings with a resulting increase in crop productivity. Recently, the recombinant DNA technology has increased the possibilities of integration of exogenous genes to the plant genome, resulting in the production of transgenic plants. Despite the great debate on this issue, such plants represent to date a promising avenue for plant breeding. There are many examples of gene transference strategies which have been successful in promoting resistance to herbicides, viruses, fungi, bacteria and insects, or in producing an increase in food quality. In addition to biotechnological applications, transgenic plants have made a significant contribution to the study of gene functioning, such as the analysis of genic expression regulation and the study of protein functions codified by distinct plant genes