Distribuição de retrotansposons do tipo LTR e sequências de DNA ribossômico em cromossomos de genótipos diploides e tetraploides de Arachis spp. por hibridização in situ por fluorescência - FISH.

O amendoim (Arachis hypogaea L.) é uma espécie alotetraploide de origem recente, originado a partir da hibridação entre duas espécies silvestres diplóides, A. duranensis (genoma A) e A.ipaënsis (genoma B), seguida por uma duplicação cromossômica espontânea (3,500-10,000 anos atrás), cujo genoma tem aproximadamente 2,8 Gb de tamanho, composto em sua maioria por sequências repetitivas. A exploração do seu genoma grande e complexo, sem o genoma de referência tem sido um desafio. Portanto, o alotetraploide sintético (A. ipaënsis x A. duranensis)4x, que mimetiza o backgraund genômico do amendoim foi utilizado com objetivo de desvendar os efeitos da hibridação e poliploidização. Esse estudo compreende a primeira caracterização citogenética dos subgenomas desse alotetraploide sintético de Arachis, em comparação com o genótipo natural, o amendoim, estendendo-se para as espécie genitoras. Os alotetraploides, natural e sintético apresentaram semelhanças, como a observada no conteúdo de DNA, com 2C (pg) de 5,71 e 5, 92 respectivamente; na intensidade e posição de bandas centroméricas DAPI+; no número de loci de DNAr 5S e em alguns loci de DNAr 45S com presença de RONs. Foi demonstrado ainda que alguns aspectos da organização e composição dos subgenomas do sintético diferem das observadas nas espécies diplóides, e em menor grau, das observadas em A. hypogaea. Rearranjos de alguns segmentos de DNA nos subgenomas do sintético foram detectados, entre eles a perda dos loci 45S de A. ipaënsis; a inativação da RON no subgenoma B; ausência de bandas evidenciando regiões heterocromáticas CMA+ e diferenças na freqüência e distribuição de RT-LTRs. Portanto a poliploidia realmente vai além da simples união de dois genomas em um mesmo núcleo, podendo envolver também a participação de vastos ajustes moleculares e fisiológicos, que incluem rearranjos genômicos, além do controle epgenético. Algumas das alterações observadas no sintético podem ser semelhantes as que possivelmente ocorreram durante a formação e evolução do amendoim. Esses resultados trazem novos insights sobre a história genômica do amendoim, representando, portanto, uma contribuição significativa para estudos relacionados com o seu contínuo sequenciamento, bem como para a compreensão geral da evolução dos genomas de Arachis.Dissertação (Mestrado em Botânica) - Instituto de Ciências Biológicas, Universidade de Brasília, Brasília, DF. Orientadora: Dra. Ana Cláudia Guerra de Araújo, Embrapa Recursos Genéticos e Biotecnologia

Molecular systematic studies in some members of the genus Senecio L. (Asteraceae)

The large body of data which is available makes some members of the genus Senecio an ideal group on which to use molecular techniques to study biosystematic problems. Three major problems have been addressed:- (i) What is the degree of intraspecific DNA variation present in Senecio cambrensis, S. squalidus and S. vulgaris sl? (ii) Did S. vulgaris ssp. vulgaris var. hibernicus originate via the introgression of S. squalidus genes into S. vulgaris ssp. vulgaris var. vulgaris? (iii) Is S. cambrensis the allohexaploid hybrid of S. squalidus and S. vulgaris sl? These questions have been addressed using both the nuclear and chloroplast genomes. It has been demonstrated that molecular evidence can provide new insights into relationships, but can also produce results which are either contradictory to other evidence or inconclusive. Intraspecific variation was encountered in Senecio squalidus and S. vulgaris sl for both the nuclear (ribosomal DNA) and chloroplast genomes. This variation has provided new insights into the relationship between the two subspecies of S. vulgaris. It is proposed that S. vulgaris sl may have originated via reciprocal crosses between Senecio species possessing different chloroplast genomes. The hybrid nature of the majority of S. cambrensis populations was confirmed, since most of the Senecio species analysed could be distinguished on the basis of their ribosomal DNAs. Molecular techniques have produced contradictory evidence regarding the relationship of Senecio sgualidus to S. vulgaris ssp. vulgaris sl. In this case the two taxa have identical chloroplast genomes. This conflicts not only with the rDNA data but also with morphology, cytology and isozymes. The possible reasons for this conflict are discussed. The ribosomal and chloroplast genomes have produced inconclusive evidence regarding the introgressive origin of Senecio vulgaris ssp. vulgaris var. hibernicus. In this thesis some of the exciting applications of molecular biology to biosystematics have been reviewed and the need for multidisciplinary approaches to biosystematic problems is emphasised

Diseases of Edible Oilseed Crops

Diseases of Edible Oilseed Crops presents an unprecedentedly thorough collection of information on the diseases of cultivated annual oilseed crops, including peanut, rapeseed-mustard, sesame, soybean, sunflower, and safflower. Written by internationally recognized researchers, this book covers and integrates worldwide literature in the field up to 2014, setting it apart from other books that are only of regional importance. The book focuses on major diseases of economic importance to each crop. Each chapter is devoted to a type of crop and a profile of affecting diseases according to geographical occurrence, epidemiology, symptoms, causal pathogens, host-pathogen interactions, biotechnological aspects, and the latest approaches to understanding host-pathogen interactions. It also includes discussions on developments on controversial subjects in research in order to stimulate thinking and further conversation with an eye toward improvements and resolutions. Research on oilseed crop diseases has expanded tremendously in the past 30 years, primarily as an effort to reduce losses to various stresses, including crop diseases. In the war against hunger and malnutrition, it is necessary to enhance and update knowledge about crop diseases and managing them. By compiling decades of information from previously scattered research into a single globally minded volume, Diseases of Edible Oilseed Crops provides these much-needed updates and enhancements

Modeling the magnetic properties of non-oriented electrical steels based on microstructural parameters

Magnetic properties of electrical steels such as magnetization behavior and electrical losses are mainly related to chemical composition, crystallographic orientation and microstructure. By now, several models have been proposed to empirically correlate magnetic properties and affecting parameters. A quantitative model based on physical understanding of the interaction between the magnetic field variables (e.g. domain structure) and local microstructural variables (e.g. grain orientation and misorientation, grain boundary plane inclination) is still missing. To obtain a better understanding of the interaction between grain boundaries and domain walls, the magnitude of free pole density at grain boundaries was taken into account. Experimental results from 3-dimentional EBSD experiments were employed to measure the grain boundary orientation for several samples with different chemical composition and grain size. The free pole density was calculated using the relative misorientation between adjacent grains, and was included in a model together with grain size, magnetocrystalline anisotropy energy and silicon equivalent. By comparison with the experimental results of the magnetic induction measured at low, medium and high magnetic fields, is shown that the magnetization behavior can be more accurately predicted when the above mentioned phenomena are taken into account

Regulation of gene expression in developing pea seeds

Three classes of legumin, encoded by the gene sub-families legA, legJ and legS, and a lectin encoded by a single gene, lecA, accumulate in the developing cotyledons of Pisum sativum L. Transcription rates for the genes encoding these proteins were measured in nuclei isolated from cotyledons at 12 and 16 days after flowering (DAF). The steady-state levels of the corresponding mRNA species were also measured, in absolute terms, throughout cotyledon development. It was found that the different legumin gene sub-families are not coordinately expressed and, in addition, members within the legJ sub-family show differential temporal expression. Also, it was demonstrated that the length of the poly (A) tail of the lectin mRNA is reduced during the period when the steady-state level of this mRNA is in decline. When transcription rates and steady-state mRNA levels of the different gene families are compared, there is little correlation. This suggests a posttranscriptional regulation of the quantitative level of expression of these genes. Expression of the legumin genes is known to be seed-specific, whereas expression of the lectin gene occurs in the root as well as the seed. When transcription rates were measured in leaf nuclei the levels of legumin and lectin transcripts detected approached background levels, indicating that these genes are either inactive or transcribed at very low levels in leaf; however, the rate of transcription of the chlorophyll a/b binding-protein gene was high. This suggests transcriptional control as the major factor in the organ-specificity of legumin and lectin expression. The apparent posttranscriptional regulation of the quantitative level of expression of different seed-protein genes was investigated further by pulse-chase labelling the RNA of pea cotyledons grown in culture. Also, the possibility of using cell-free extracts to assay the cytoplasmic stability of specific polysomal mRNAs was investigated