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Zugl.: Berlin, Humboldt-Univ., Diss., 2009

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A expansão dos locais e da época de cultivo do milho faz com que uma fração significativa da produção do cereal ocorra em condições de estresses abióticos. Grande parte desse cenário edafoclimático remete ao cultivo do milho safrinha, semeado entre janeiro e março e atualmente responsável por 65% da produção total. Dentre os diversos tipos de estresses abióticos, a deficiência de nitrogênio é comum e crítica nos solos brasileiros. Evidencia-se, portanto, a necessidade do desenvolvimento de genótipos mais eficientes no uso de nitrogênio, resultando em benefícios econômicos e ambientais. Caracteres morfofisiológicos podem auxiliar no processo seletivo de genótipos superiores para essas condições, como a mensuração do sistema radicular e a análise da taxa fotossintética. Nesse contexto, o objetivo do trabalho foi identificar regiões do genoma do milho tropical associadas ao comprimento de raiz, à fluorescência de clorofila e ao índice de resposta da planta ao estresse por nitrogênio. Para isto, foram avaliadas 64 linhagens endogâmicas de milho tropical em baixa e alta disponibilidade nitrogênio no solo e em dois locais de cultivo na Região de Piracicaba-SP, nas safras 2014/15 e 2015/16. Foram considerados o comprimento de raiz, a eficiência fotossintética do fotossistema II e o Índice de Tolerância à Baixa disponibilidade de nitrogênio (ITBN). As linhagens foram genotipadas com a plataforma Affymetrix® Axiom® Maize Genotyping Array de 616.201 marcadores SNP. A qualidade da informação genômica foi controlada pelos procedimentos Minor Allele Frequency e Call Rate e pela eliminação de heterozigotos. Os valores genotípicos foram preditos por meio de equações de modelos mistos do tipo REML/BLUP. Os dados de marcadores moleculares e fenotípicos foram analisados por Associação Genômica Ampla (GWAS). Verificou-se maior comprimento radicular em condições de baixa disponibilidade de nitrogênio. No total, sete marcadores significativos foram identificados, sendo quatro referentes ao ITBN, dois referentes ao comprimento de raiz em disponibilidade ideal e um referente ao comprimento de raiz em disponibilidade baixa do nutriente. Entre os principais processos biológicos identificados através da anotação funcional, estão o controle e regulação da transcrição, detectado para todos os caracteres avaliados, e a síntese de Guanosina Monofosfato Sintetase (GMP), enzima diretamente envolvida na disponibilização e reciclagem de nitrogênio. Também foi observada coincidência de região cromossômica entre marcadores significativos identificados e QTL potencialmente relacionados com a eficiência no uso de nitrogênio já reportados na literatura. Conclui-se que a técnica GWAS apresenta eficiência na detecção de marcadores associados aos caracteres de interesse, neste caso evidenciando processos e funções celulares relacionados aos diferentes processos da síntese e reciclagem de nitrogênio. / The expansion of locals and season period of maize crop makes a significant portion of the cereal production to occur under abiotic stress conditions. Much of this environmental scenario refers to the second growing season maize, sowed between January and March and responsible for 65% of total production currently. Among the different types of abiotic stresses, nitrogen deficiency is common and critical in Brazilian soils. Therefore, it becomes necessary to develop genotypes more efficient in nitrogen use, resulting in economic and environmental benefits. Morphophysiological characters may assist in the selective process of superior genotypes for these conditions, such as root system measurement and photosynthetic ratio analysis. In this context, this project aimed to identify tropical maize genomic regions associated with root morphological character, physiological parameter of photosystem II, and with the plant response index to nitrogen stress. To this end, 64 tropical maize inbreeding lines contrasting for nitrogen use efficiency were evaluated in low and ideal soil nitrogen availability in two cultivation sites in the region of Piracicaba-SP, in seasons 2014/15 and 2015/16. The characters root total length, chlorophyll fluorescence, and Low Nitrogen Tolerance index (LNTI) were considered. The lines were genotyped SNP using the Affymetrix® Axiom® Maize Genotyping Array with 616,201 SNP. The quality of the genomic information was controlled by Minor Allele Frequency and Call Rate procedures and by the elimination of heterozygous loci. The genotypic values were predicted using REML/BLUP mixed model equations. Genome-Wide Association Studies (GWAS) was performed to analyze molecular and phenotypic data. Greater root length under low availability nitrogen conditions was verified. In total, seven significant markers were identified, four referring to LNTI, two referring to root length under ideal nitrogen availability and one referring to root length under low nitrogen availability. Among the main biological processes identified trough functional annotation are the transcription control and regulation, detected to all evaluated characters, and the synthesis of Guanosine Monophosphate Synthetase (GMP), enzyme directly involved in the provision and recycling of nitrogen. It was also observed coincidence of chromosomal region between significant markers identified and QTLs potentially related in nitrogen use efficiency previously reported. As conclusion, GWAS technique shows efficiency in the detection of markers associated to the characters in focus, in this evidencing cellular processes and functions associated to the different process of nitrogen synthesis and recycling.

Relative Orientation of EFG Tensors of Half-integer Quadupolar Nuclei Studied by 3D MQMAS Spin Diffusion Spectroscopy

Soybean [Glycine max (L.) Merrill] is an important source of protein and oil for both nutritional and industrial applications. Increasing seed yield and protein concentration is the main goal of many soybean breeders to meet market demands. Soybean breeders have occasionally succeeded in producing high yielding cultivars with increased protein content using conventional means despite the negative correlation that exists between these two traits. The efficiency of breeding for seed yield and protein concentration improvement in soybean could be increased using marker assisted selection (MAS) breeding strategies to select genotypes containing favorable alleles for faster cultivar development. The objective of this study was to identify quantitative trait loci (QTL) associated with seed yield, and separately, seed protein concentration and then compare phenotypic selection (PHE) and MAS approaches for seed yield and protein concentration improvement. Two hundred and eighty two F5 derived recombinant inbred lines (RILs) were developed from a cross of Essex × Williams 82 and genotyped with 1586 single nucleotide polymorphism (SNP) markers. The population was divided by days to maturity (10 days) into three tests (early, mid and late) each with 94 genotypes, with one genotype overlapping in maturity in the mid and late tests. In 2009, the three tests, parents and checks were grown in a randomized complete block design (RCBD) in: Fayetteville, AR; Harrisburg, IL and, Knoxville, TN replicated three times, and evaluated for seed yield and protein concentration. Data were combined within each test across three locations and analyzed using the MIXED procedure of SAS to determine that there were significant genotypic differences among RILs. Composite interval mapping (CIM) detected nine seed yield and ten protein concentration QTL which may be good candidates for MAS as they were environmentally stable. Selections to compare PHE, and MAS for seed yield and protein concentration provided 8 replicated field tests in four relative maturity groups grown in a RCBD replicated three times in three locations in Tennessee, in 2010. We demonstrated that both MAS and PHE may be used to select quantitative traits; however, more studies are required to optimize MAS for quantitative trait improvement. 

Proefschrift Universiteit van Amsterdam. / Auteursnaam op omslag: René B. Karels. Met lit.opg. en index. - Met samenvatting in het Engels.

The mas proto-oncogene encodes a seven transmembrane protein (MAS) which is suggested to function as a receptor for angiotensin. It (MAS) was initially identified in NIH-3T3 cells that were transformed with DNA isolated from a human epidermoid carcinoma. These cells formed foci in culture and tumors when injected into nude mice. On the other hand, untransformed cells did not. Further analysis of these cells showed that transformed cells bind increased levels of angiotensin when compared to untransformed cells. These studies also demonstrated that the Mas protein was structurally similar to the angiotensin receptor transmembrane proteins, AT1 and AT2 . This investigation was undertaken to examine the ability of the Mas protein to function as an receptor for angiotensin and promote cell proliferation. To this end, quantitation of mas genes by Polymerase Chain Reaction (PCR) and serial dilutions, and Southern blot analysis support an increased in mas genes in transformed cells. Northern blot analysis demonstrated an increased expression of the mas gene in transformed cells. No changes in the level of the AT2 angiotensin receptor gene expression was observed in the transformed and untransformed cell lines. Expression of the AT1 angiotensin receptor gene was not observed in these cell lines. Anti-peptide antibodies were generated against the 1st and 2nd extracellular regions of the Mas protein. Flow cytometric analysis using these antibodies indicated an increased presence of the Mas protein on the surf ace of transformed cells recognized by anti-peptide antibodies. Western blot analysis showed two cross-reacting proteins of approximately ll0kd and 66kd in transformed cells; whereas, only a 66kd protein was found in untransformed cells. Transformed cells exposed to mas antisense oligos greatly reduced the synthesis of Mas, decreased cell proliferation and the binding of angiotensin. Binding studies using [3H]-DUP- 753 (a non-peptidyl ligand which recognizes Ang subtype AT1 receptors) showed little binding to transformed cells. Similar studies using PD-123319 (a non-peptidyl ligand that recognizes AT2 subtype receptors) indicated that approximately 60% of [125I]-Ang II was displaced using PD-123319. Further binding analysis of transformed cells suggests that [Sarl]-Ang II (an Ang II antagonist) could not completely displace [ 125I]-Ang II. Taken together, these data suggest that Mas protein is an Ang receptor which functions in the regulation of cell proliferation. Mas appears to be a member of a subtype different from AT1 or AT2.

Zugl.: Berlin, Humboldt-Univ., Diss., 2009

Universiẗat, Diss--Köln, 2004. / Zusfassung in dt. und engl. Sprache.