Impacts of nymph/worker genotypes on termite incipient colony fitness

Dissertação de mestrado em Biologia Celular e Molecular, apresentada ao Departamento de Ciências da Vida da Faculdade de Ciências e Tecnologia da Universidade de Coimbra.A antraciclina Doxorrubicina (DOX) é um dos mais usados agentes antineoplásicos. No entanto, o tratamento com este composto está associado com cardiotoxicidade, que é dependente da dose e da sua acumulação. A mitocondrial Sirtuína 3 (Sirt3) é a maior deacetilase mitocondrial, modulando diversas vias, tal como a apoptose e o metabolismo celular. Assim a nossa hipótese é que a actividade da Sirt3 diminui a cardiotoxicidade induzida pela DOX. Os cardiomioblastos H9c2 foram transfectados com siRNA e plasmídeos para produzir células com Sirt3 silenciada e sobreexpressa, respectivamente. A toxicidade da DOX (0.5 e 1 µM) foi avaliada pelo ensaio da Sulforodamina B e por citometria de fluxo. A despolarização mitocondrial e a produção do anião superóxido foi determinada por microscopia de fluorescência e o conteúdo de proteínas específicas por western blot. A sobre e sub-expressão da Sirt3 foi confirmada por western blot e RT-PCR. A toxicidade da DOX envolveu a indução de morte celular em todos os grupos. O aumento do conteúdo de Sirt3 mediado pela sobreexpressão parece diminuir a toxicidade da DOX, maioritariamente pela manutenção da integridade da rede mitocondrial e redução do stress oxidativo. Por outro lado, a p53 parece ser um alvo directo da Sirt3 e a protecção conferida contra a morte celular pela Sirt3 pode ser relacionada com esta proteína.The anthracycline Doxorubicin (DOX) is one of the most widely used anti-neoplastic agents. However, treatment with this drug is associated with a cumulative and dose dependent cardiotoxicity. Mitochondrial Sirtuin 3 (Sirt3) is the major mitochondrial deacetylase, modulating several pathways, such as apoptosis and metabolism. Thus, our hypothesis is that mitochondrial Sirt3 activity decreases DOX-induced cardiotoxicity. H9c2 cardiomyoblasts were transfected with siRNA and a plasmid construct to produce Sirt3 knock-down and Sirt3 overexpressing cells, respectively. DOX (0.5µM and 1µM) toxicity was evaluated by the Sulforhodamine B assay and by flow cytometry using the Life/Death assay. Mitochondrial depolarization and superoxide production was determined by fluorescence microscopy and content in specific proteins by western blot. Sirt3 overexpression or knock-down was confirmed by Western Blot and qRT-PCR. In all experimental groups, DOX induced cell death. Increase in Sirt3 content by transfection-mediated overexpression appeared to decrease DOX toxicity, most by maintaining the integrity of mitochondrial network and reducing oxidative stress. On the other hand, p53 seems to be a direct target of Sirt3 and the protection against cell death conferred by Sirt3 could be related to this protein

The Arabidopsis \u3cem\u3edwf/ste1\u3c/em\u3e Mutant is Defective in the Δ\u3csup\u3e7\u3c/sup\u3e Sterol C-5 Desaturation Step Leading to Brassinosteroid Biosynthesis

Lesions in brassinosteroid (BR) biosynthetic genes result in characteristic dwarf phenotypes in plants. Understanding the regulation of BR biosynthesis demands continued isolation and characterization of mutants corresponding to the genes involved in BR biosynthesis. Here, we present analysis of a novel BR biosynthetic locus, dwarf7 (dwf7). Feeding studies with BR biosynthetic intermediates and analysis of endogenous levels of BR and sterol biosynthetic intermediates indicate that the defective step in dwf7-1 resides before the production of 24-methylenecholesterol in the sterol biosynthetic pathway. Furthermore, results from feeding studies with 13C-labeled mevalonic acid and compactin show that the defective step is specifically the Δ7 sterol C-5 desaturation, suggesting that dwf7 is an allele of the previously cloned STEROL1 (STE1) gene. Sequencing of the STE1 locus in two dwf7 mutants revealed premature stop codons in the first (dwf7-2) and the third (dwf7-1) exons. Thus, the reduction of BRs in dwf7 is due to a shortage of substrate sterols and is the direct cause of the dwarf phenotype in dwf7

The Arabidopsis \u3cem\u3edwarf1\u3c/em\u3e Mutant is Defective in the Conversion of 24-Methylenecholesterol to Campesterol in Brassinosteroid Biosynthesis

Since the isolation and characterization of dwarf1-1 (dwf1-1) from a T-DNA insertion mutant population, phenotypically similar mutants, including deetiolated2 (det2),constitutive photomorphogenesis and dwarfism(cpd), brassinosteroid insensitive1 (bri1), and dwf4, have been reported to be defective in either the biosynthesis or the perception of brassinosteroids. We present further characterization of dwf1-1 and additional dwf1 alleles. Feeding tests with brassinosteroid-biosynthetic intermediates revealed that dwf1 can be rescued by 22α-hydroxycampesterol and downstream intermediates in the brassinosteroid pathway. Analysis of the endogenous levels of brassinosteroid intermediates showed that 24-methylenecholesterol in dwf1 accumulates to 12 times the level of the wild type, whereas the level of campesterol is greatly diminished, indicating that the defective step is in C-24 reduction. Furthermore, the deduced amino acid sequence of DWF1 shows significant similarity to a flavin adenine dinucleotide-binding domain conserved in various oxidoreductases, suggesting an enzymatic role for DWF1. In support of this, 7 of 10 dwf1 mutations directly affected the flavin adenine dinucleotide-binding domain. Our molecular characterization of dwf1 alleles, together with our biochemical data, suggest that the biosynthetic defect in dwf1 results in reduced synthesis of bioactive brassinosteroids, causing dwarfism