Claudete Clarice Mistura

Abiotic stress and genome dynamics: specific genes and transposable elements response to iron excess in rice.

BackgroundIron toxicity is a root related abiotic stress, occurring frequently in flooded soils. It can affect the yield of rice in lowland production systems. This toxicity is associated with high concentrations of reduced iron (Fe2+) in the soil solution. Although the first interface of the element is in the roots, the consequences of an excessive uptake can be observed in several rice tissues. In an original attempt to find both genes and transposable elements involved in the response to an iron toxicity stress, we used a microarray approach to study the transcriptional responses of rice leaves of cv. Nipponbare (Oryza sativa L. ssp. japonica) to iron excess in nutrient solution.ResultsA large number of genes were significantly up- or down-regulated in leaves under the treatment. We analyzed the gene ontology and metabolic pathways of genes involved in the response to this stress and the cis-regulatory elements (CREs) present in the promoter region of up-regulated genes. The majority of genes act in the pathways of lipid metabolic process, carbohydrate metabolism, biosynthesis of secondary metabolites and plant hormones. We also found genes involved in iron acquisition and mobilization, transport of cations and regulatory mechanisms for iron responses, and in oxidative stress and reactive oxygen species detoxification. Promoter regions of 27% of genes up-regulated present at least one significant occurrence of an ABA-responsive CRE. Furthermore, and for the first time, we were able to show that iron stress triggers the up-regulation of many LTR-retrotransposons. We have established a complete inventory of transposable elements transcriptionally activated under iron excess and the CREs which are present in their LTRs.ConclusionThe short-term response of Nipponbare seedlings to iron excess, includes activation of genes involved in iron homeostasis, in particular transporters, transcription factors and ROS detoxification in the leaves, but also many transposable elements. Our data led to the identification of CREs which are associated with both genes and LTR-retrotransposons up-regulated under iron excess. Our results strengthen the idea that LTR-retrotransposons participate in the transcriptional response to stress and could thus confer an adaptive advantage for the plant.

Caracterização molecular de variedades crioulas de pimentas (Capsicum baccatum) com marcadores microssatélites

Currently, many landraces of C. baccatum are grown by farmers in Brazil. These populations are sources of genes for resistance or tolerance to abiotic and biotic stresses. However, most of these landraces are being lost due to genetic erosion caused by substitution of cultivars. In order to characterize and conserve landraces, since 2002 Embrapa Temperate Agriculture maintains an Active Germplasm Bank of Capsicum. This work has the objective to characterize landraces of C. baccatum using microsatellite markers. 20 accessions from the Active Germplasm Bank of Capsicum of Embrapa Temperate Agriculture were analyzed. DNA was extracted individually from young leaves collected from five plants of each accession. Eight microsatellite loci were analyzed. All loci were polymorphic. Molecular analysis of variance showed values of genetic diversity as 51.37% among accessions and 48.63% within the accessions. This fact showed the existence of segregation in many of these pepper landraces. The groups obtained by cluster analysis did not correlate with morphological fruit traits. Most of the genetic variability is found among different landraces, although there is also genetic variability within each accession.

Diversidade genética de Cucurbita pepo, C. argyrosperma e C. ficifolia empregando marcadores microssatélites

Genetic diversity of Cucurbita pepo, C. argyrosperma and C. ficifolia accessions evaluated through microsatellite markers Landraces of five domesticated species of Cucurbita are cultivated in southern Brazil. Among them C. argyrosperma and C. ficifolia are the least studied. Microsatellite markers are important for the molecular characterization of these two species, but there is a need for specific primers, not yet available. The aim of this study was to evaluate the transferability of primers and optimize the amplification of SSR loci in C. pepo, C. argyrosperma and C. ficifolia and also evaluate genetic diversity in different accessions of germplasm in these species. We used ten accessions of C. pepo, nine of C. argyrosperma and five of C. ficifolia from the Genebank of Cucurbitaceae from Embrapa Temperate Agriculture. DNA was extracted in bulk from the leaves of five individuals of each accession. 40 SSR primers developed for C. pepo were used. In C. pepo 35 primers (87.5%) amplified, in C. argyrosperma, 34 primers (85%), and in C. ficifolia , 32 primers (80%). The transferability of SSR loci in C. pepo to C. argyrosperma and C. ficifolia was 85 and 80% respectively. The transferability of SSR loci from C. pepo to C. argyrosperma and C. ficifolia was 85 and 80% respectively. Thus, the transferability rate of SSR loci developed for C. pepo to C. argyrosperma and C. ficifolia was high, indicating that they can be used in molecular characterization of these species.

Determinação da dissimilaridade genética entre acessos de Capsicum chinense com base em características de flores

Genetic dissimilarity among Capsicum chinense accessions based on flower characteristics Capsicum peppers are extremely important in Brazil for the spice market and as ornamental. The estimation of genetic diversity is important for the choice of parents in a breeding program. This study aimed to evaluate the efficiency of multicategoric descriptors for flowers to estimate the genetic dissimilarity among Capsicum chinense accessions from the Capsicum Active Germplasm Bank of Embrapa Temperate Agriculture The experiment was conducted from October 2009 to March 2010 in the experimental field of Embrapa Temperate Agriculture, with 22 accessions evaluated in randomized blocks and ten plants per plot. Five flowers of each plant, ten plants per access were used for the morphological characterization of the flowers. Five quantitative and ten qualitative multicategoric descriptors were used, making a total of 15. Mean comparison tests were carried out, and the clustering methods UPGMA and Tocher

Caracterização molecular de variedades crioulas de abóboras com marcadores microssatélites

Dentre as cinco especies de aboboras domesticadas, Cucurbita pepo apresenta a maior variabilidade para caracteristicas de fruto, como cor, formato e tamanho. O Banco Ativo de Germoplasma de Cucurbitaceas da Embrapa Clima Temperado conta com 61 acessos desta especie, todos estes, variedades crioulas cultivadas no sul do Brasil. Estas variedades crioulas fazem parte da cultura regional, na gastronomia, no artesanato e na ornamentacao de ambientes. O objetivo deste trabalho foi avaliar a variabilidade genetica entre e dentro de variedades crioulas de C. pepo cultivadas no Rio Grande do Sul, utilizando marcadores microssatelites. Foram avaliados 10 acessos de variedades crioulas de C. pepo. que apresentavam diferentes formatos e tamanhos de fruto, cores e texturas da casca. O DNA genomico foi extraido individualmente de cinco plantas de cada acesso. Foram analisados 40 locos de microssatelites. Destes, 34 amplificaram, identificando 100 alelos (variacao de um a cinco alelos por loco). Dos locos analisados 85,3% foram polimorficos, evidenciando a variabilidade genetica entre os acessos. A analise molecular da variância mostrou que 45,39% da variabilidade genetica e atribuida a variacao dentro dos acessos e 54,60% a diferencas entre acessos. Assim, apesar de haver variabilidade genetica dentro dos acessos, a maior proporcao da variabilidade em C. pepo encontra-se distribuida entre as diferentes variedades crioulas. A variacao dentro dos acessos e explicada pela alogamia da especie, pelo intercâmbio de sementes das variedades crioulas entre os agricultores e tambem pelos mesmos cultivarem mais de uma variedade de Cucurbita na mesma area.