Las levaduras silvestres presentan una acusada inestabilidad cariotípica durante el crecimiento vegetativo. Hemos analizado alrededor de 500 cariotipos de derivados mitóticos y meióticos de la cepa vínica silvestre DC5, la cual presenta una frecuencia de inestabilidad cariotípica de 8.2x10-2 cambios/clon/generación. Un 70 % de los derivados meióticos de DC5 presentó una baja frecuencia de inestabilidad cariotípica, con una media de 5.8x10-4 cambios/clon/generación, sugiriendo que la inestabilidad cariotípica es un fenotipo de carácter dominante. Los derivados diploides con una baja tasa de inestabilidad cariotípica mitótica, también presentaron una baja tasa de inestabilidad cariotípica en meoisis, sugiriendo que los dos fenotipos están ligados. La cepa DC5 y alguno de sus derivados meióticos (tanto los de baja como los de alta frecuencia de variabilidad cariotípica) presentaron una manifiesta hipervariabilidad en el cromosoma XII, aunque esta no es un indicativo de inestabilidad genética. Los derivados cariotípicamente inestables, pueden dar lugar a derivados estables con una alta frecuencia.La inestabilidad genética de una cepa dificulta la posibilidad de aplicar programas de mejora genética en ésta para su aplicación industrial. La inestabilidad cariotípica es un fenómeno de carácter dominante, y que depende de pocos elementos genéticos. La disrupción del gen RAD52 en una cepa hipervariable, estabiliza parcialmente su cariotipo. Concretamente la disrupción de RAD52 elimina la recombinación subtelomérica y telomérica, no influye en la hipervariabilidad del cromosoma XII y reduce en un 30% la frecuencia de inestabilidad cariotípica. Por consiguiente, existen al menos tres mecanismos relacionados con la inestabilidad cariotípica en cepas salvajes, de los que dos son independientes de recombinación homóloga- RAD52. El mutante rad52 presentó un fitness industrial equiparable a la cepa salvaje, en la segunda fermentación del cava, en concreto en lo que a capacidad de fermentación vigorosa se refiere. El aislamiento físico y el análisis de algunas variantes de tamaño del cromosoma I en estas cepas, mostró como estas diferían en las regiones subteloméricas, permaneciendo el cuerpo central cromosómico de 150 Kb inalterado. El mapeo fino de dichas regiones subteloméricas, mostró grandes alteraciones en dos loci muy similares, FLO1 y FLO9. Estos loci se localizan en los brazos derecho e izquierdo del cromosoma I. Estos genes poseen secuencias repetidas internas. Algunas variantes del cromosoma I que carecen del gen FLO1 mostraron un evidencias de procesos recombinatorios en regiones del brazo derecho que contienen LTRs y Tys. Por lo tanto proponemos que las secuencias repetidas en algunas regiones subteloméricas de S.cerevisiae pueden jugar un papel la hipervariabilidad cariotípica. Algunas de dichas secuencias codifican proteínas de membrana y de interacción con el medio, por lo que la plasticidad subtelomérica puede implicar un mecanismo de adaptación a substratos específicos. Este patrón semi conservativo de reorganizaciones cromosómicas puede tener importantes implicaciones, tanto desde un punto de vista evolutivo como para diferentes procesos biotecnológicos. / Yeast strains isolated from the wild may show high rates of changes in their karyotypes during vegetative growth. We analysed over 500 karyotypes from mitotic and meiotic derivatives of strain DC5, which has a chromosome rearrangement rate of 8.2x10-2 changes/generation. About 70% of the meiotic derivatives of DC5 had low rearrangement rates, with an average of 5.8x10-4 changes/generation, suggesting that karyotype instability behaved as a dominant phenotype. Diploid derivatives with low karyotype variability in mitosis also had low rates of chromosomal rearrangement during meiosis, suggesting that the two phenotypes may be linked. DC5 and some of its meiotic derivatives (both with high and low karyotype variability) had chromosome XII hypervariable bands. Their distribution among the meiotic products indicates that they are not indicators for genetic instability. Karyotypically unstable yeast strains may give stable progeny at high rates. The genetic instability compromises their utility in genetic improvement projects for industrial purposes. Karyotype instability is a dominant trait, segregating among meiotic derivatives as if it depended upon only a few genetic elements. We show that disrupting the RAD52 gene in a hypervariable strain partially stabilizes its karyotype. Specifically, RAD52 disruption eliminated recombination at telomeric and subtelomeric sequences, had no influence on ribosomal DNA rearrangement rates, and reduced to 30% the rate of changes in chromosomal size. Thus, there are at least three mechanisms related to karyotype instability in wild yeast strains, two of them not requiring RAD52-mediated homologous recombination. When utilized for a standard sparkling-wine second fermentation, rad52 strains retained the enological properties of the parental strain, specifically its vigorous fermentation capability. Physical isolation and analysis of several chromosome I size variants of one of these strains revealed that they differed only in their subtelomeric regions, leaving the central 150 Kb unaltered. Fine mapping of these subtelomeric variable regions revealed gross alterations of two very similar loci, FLO1 and FLO9. These loci are located on the right and left arms, respectively, of chromosome I and encompass internal repetitive DNA sequences. Furthermore, some chromosome I variants lacking the FLO1 locus showed evidence of recombination at a DNA region on their right arm that is enriched in repeated sequences, including Ty LTRs. We propose that repetitive sequences in many subtelomeric regions in S. cerevisiae play a key role in karyotype hypervariability. As these regions encode several membrane-associated proteins, subtelomeric plasticity may allow rapid adaptive changes of the yeast strain to specific substrates. This pattern of semi-conservative chromosomal rearrangement may have profound implications, both in terms of evolution of wild strains and for biotechnological processes.

Submitted by Nathália Faria da Silva (nathaliafsilva.ufv@gmail.com) on 2017-06-14T18:25:04Z No. of bitstreams: 1 resumo.pdf: 15350 bytes, checksum: dfb862c1ae844570018456c3a9ff28f4 (MD5) / Made available in DSpace on 2017-06-14T18:25:04Z (GMT). No. of bitstreams: 1 resumo.pdf: 15350 bytes, checksum: dfb862c1ae844570018456c3a9ff28f4 (MD5) Previous issue date: 2005-02-14 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / O objetivo deste trabalho foi padronizar as condições de obtenção e regeneração de protoplastos de Epulorhiza repens e Ceratorhiza sp. e determinar o cariótipo eletroforético de Ceratorhiza sp. Para o fungo Epulorhiza repens, a maior produção de protoplastos, 8,0 x 10 6 protoplastos/mL, foi obtida em KCl 0,6 M, na presença de 15 mg/mL de “Lysing Enzymes” e 0,5 g de micélio fúngico com 2 dias idade, após fragmentação em liquidificador. A maior freqüência de regeneração obtida foi de 8,5 % quando sacarose 0,5 M foi utilizada como estabilizador osmótico. Do total de protoplastos obtidos, 58,6 % eram uninucleados, 21,4 % binucleados e 20 % anucleados. Para o fungo Ceratorhiza sp., a maior produção de protoplastos, 4,0 x 10 7 protoplastos/mL, foi obtida em NaCl 0,6 M, na presença de 15 mg/mL de “Lysing Enzymes” e 15mg/mL de Glucanex, 0,5 g de micélio fúngico com 2 dias de idade, após fragmentação em liquidificador. A maior freqüência de regeneração obtida foi de 6,7 % utilizando sacarose 0,5 M como estabilizador osmótico. Do total de protoplastos obtidos, 61 % eram uninucleados, 24,6 % binucleados, 3,2 % trinucleados e 11,2 % anucleados. O cariótipo eletroforético do fungo Ceratorhiza sp. apresentou no mínimo, 3 cromossomos cujos tamanhos foram estimados em 4,6; 3,5 e 2,2 Mb. A maior intensidade da banda de 4,6 Mb sugere que esta possa estar representando dois cromossomos, sendo o tamanho do genoma estimado em pelo menos 14,9 Mb. O estabelecimento de protocolos otimizados para obtenção e regeneração de protoplastos dos fungos Epulorhiza repens e Ceratorhiza sp. é importante, permitindo o estabelecimento de técnicas de transformação genética, o isolamento de mutantes, a determinação de cariótipo eletroforético e o cruzamento de linhagens. O cariótipo de Ceratorhiza sp. é importante para a determinação do número e do tamanho dos cromossomos, para se estimar o tamanho do genoma e a localização de genes relacionados à formação de micorrizas. / This study was conducted in order to standardize the formation conditions and regeneration of Epulorhiza repens and Ceratorhiza sp. protoplasts and also to determine the electrophoretic karyotype of Ceratorhiza sp. For Epulorhiza repens, the highest production of protoplasts, 8,0 x 10 6 protoplasts/mL, was obtained in KCl 0,6 M, with 15 mg/mL of “Lysing Enzymes” and 0,5 g of mycelium at 2 days, after fragmentation in the liquefier. The best regeneration frequency, 8,5 %, was achieved when sucrose 0,5 M was used as an osmotic stabilizer. From total protoplasts obtained, 58,6 % were uninucleate, 21,4 % binucleate and 20 % anucleate. For Ceratorhiza sp. the highest production of protoplasts, 4,0 x 10 7 protoplasts/mL, was obtained in NaCl 0,6 M, with 15 mg/mL of “Lysing Enzymes” and 15 mg/mL of Glucanex, and 0,5 g of mycelium at 2 days, after fragmentation in the liquefier. The best regeneration frequency, 6,7 %, was achieved when sucrose 0,5 M was used as an osmotic stabilizer, and from total protoplasts obtained, 61 % were uninucleate, 24,6 % binucleate, 3,2 % trinucleate and 11,2 % anucleated. The electrophoretic karyotype of Ceratorhiza sp. showed at least 3 chromosomes around 4,6; 3,5 and 2,2 ixMb. The highest intensity of the band 4,6 Mb suggests that it represents two chromosomes, and the genome height was estimated in, at least, 14,9 Mb. It is important to establish optimized protocols for obtaining and regenerating protoplasts of Epulorhiza repens and Ceratorhiza sp. to allow the establishment of techniques of genetic transformation, mutant isolation, electrophoretic karyotype determination and crossings between strains. Ceratorhiza sp. karyotype is important to determine chromosomes number and height, to estimate genome height and gene localization related to mycorrhizas formation.

Made available in DSpace on 2017-07-21T19:59:47Z (GMT). No. of bitstreams: 1 Miguel Soto.pdf: 3392628 bytes, checksum: 62e83dd8713fab1173dd8f45d005072c (MD5) Previous issue date: 2017-02-22 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Within the great biodiversity of freshwater fish of South America, the Characidae family has been one of the most controversial groups taxonomically. In the trans-Andean country of Chile, the family is represented only by the Cheirodontinae of the genus Cheirodon and its five species, of which C. pisciculus, C. galusdae, C. kiliani and C. australe are endemic, and C. interruptus is native to the Atlantic basins of Argentina, Uruguay and Brazil. In order to contribute to the description of the evolutionary relationships and taxonomic delimitation of the species of genus Cheirodon present in Chile, the karyotypes of these five species are described for the first time and compared by their diploid number, chromosomic morphology, C bands, Nucleolar Organizer Regions (Ag-NOR) and the rDNA 5S and 18S marking by fluorescence in situ hybridization (FISH). For all the analyzed species the diploid number was 50 chromosomes, varying in the karyotype formula among the metacentric, submetacentric, subtelocentric and acrocentric types. The number of chromosome arms was 68 in C. australe and C. kiliani and 66 in C. galusdae, C. pisciculus and C. interruptus. The presence and distribution of constitutive heterochromatin was similar in the five species, being observed mainly in the centromeres and telomeres. Variation in the number and distribution of the 5S and 18S rDNA regions was observed, being those two clusters on different chromosomes or in syntenia. It was also observed a variation in the activity of RONs, being found in C. kiliani and C. galusdae, the highest level of relative activity. There is a greater karyotype similarity between the two species that living more to the south in relation to those with the most central and north distribution, evidencing a reflection of hydrograph formation and species isolation. / Dentro da grande biodiversidade de peixes de água doce de América do Sul,a família Characidae tem sido um dos grupos mais controversos taxonomicamente. No país transandino Chile, a família é representada apenas pelos Cheirodontinae do gênero Cheirodon e suas cinco espécies, das quais C. pisciculus, C. galusdae, C. kiliani e C. australe são endêmicas. No entanto C. interruptus é originaria das bacias atlânticas da Argentina, Uruguai e Brasil. Para contribuir na descrição das relações evolutivas e delimitação taxonômica das espécies do gênero Cheirodon presentes no Chile, são descritos pela primeira vez os cariótipos destas cinco espécies e comparados segundo seu número diplóide, morfologia cromossômica, bandas C, Regiões Organizadoras do Nucléolo (Ag-RON) e a marcação de DNAr 5S e 18S por hibridação in situ fluorescente (FISH). Para todas as espécies analisadas o número diplóide foi de 50 cromossomos, variando na fórmula cariotípica entre os tipos metacêntricos, submetacêntricos, subtelocêntricos e acrocêntricos. O número de braços cromossômicos foi de 68 em C. australe e C. kiliani e de 66 em C. galusdae, C. pisciculus e C. interruptus. A presença e distribuição da heterocromatina constitutiva foi similar nas cinco espécies, sendo observada principalmente nos centrômeros e telômeros. Foi observada variação no número e distribuição das regiões de DNAr 5S e 18S, podendo esses dois clusters estar em cromossomos diferentes ou em sintenia. Também foi observada variação na atividade das RONs, sendo encontrado em C. kiliani e em C. galusdae, o maior nível de atividade relativa. Existe maior similaridade cariotípica entre as duas espécies ocorrentes mais ao sul do que destas em relação àquelas mais centrais e ao norte, mostrando um reflexo da formação da hidrografia e isolamento das espécies.

MATERIAL I MÈTODES: En el primer estudi es van analitzar els resultats de l’aplicació del Test Combinat (bioquímica materna de primer trimestre (f-β-hCG i PAPP-A) i la mesura de la translucència nucal (TN) d’ambdós fetus a les 11-14 s) per a la detecció de trisomia 21 en 100 gestacions gemel•lars. Es va comparar l’ efectivitat del Test Combinat amb el cribratge exclusivamnet ecogràfic mitjançant la medició de la TN. En un segon temps es van analitzar els resultats obtinguts amb el Test Combinat en 161 gestacions gemel•lars. Es va analitzar també la distribució dels marcadors bioquímics de primer trimestre en funció de la corionicitat i del tipus de reproducció (espontània o assistida). En el segon estudi es van valorar els resultats obtinguts en totes les gestacions gemel•lars (monocorials i dicorials) amb un o ambdós fetus amb una TN extrema (> percentil 99) diagnosticats durant l’ecografia de primer trimestre, en un període de 4 anys. CONCLUSIONS: . Dels resultats del primer estudi es desprèn que l’aplicació del Test Combinat permet en les gestacions gemel•lars, disminuir els falsos positius obtinguts amb l’aplicació del cribratge exclusiu ecogràfic (14.3% de les gestacions vs 5.1%) i que els marcadors bioquímics de primer trimestre presenten uns valors significativament disminuits en les gestacions monocorials respecte a les gestacions dicorials. Els resultats del segon estudi mostren que la prevalença d’una TN extrema és major en els fetus procedents d’una gestació monocorial i que una TN extrema en algun dels fetus s’associa a resultats obstètrics desfavorables (80%) tant en les gestacions monocorials com dicorials. PARAULES CLAU: Gestació gemel•lar; Test Combinat; cribratge de trisomia 21; cribratge de primer trimestre; translucència nucal; translucència nucal augmentada; cariotip normal; defectes estructurals; síndrome de transfusió feto-fetal. / Methods: In the first study, free-β-hCG and PAPP-A were determined at 8-12 weeks and fetal nuchal translucency (NT) was measured at 11-14 weeks in 100 twin pregnancies. The individual risks for trisomy 21 were estimated using NT alone and the Combined Test and the effectiveness of both tests was compared. Subsequently, the results of the combined test were evaluated in 161 twin pregnancies with an assessment on the distribution of the biochemical markers ant NT thickness according to chorionicity and the mode of conception. In the second study a consecutive sample of 206 twin pregnancies (166 dichorionic and 40 monochorionic) were scanned for NT. In those with a NT>99th percentile and a normal karyotype, extensive follow-up was performed and perinatal outcome was recorded. Results:. In the first study, two pregnancies with trisomy 21 were detected by both methods. The false positive rate achieved by NT screening (11.2% of pregnancies) was substantially reduced when first trimester biochemistry was added (5.1%). With the application of the Combined Test in 161 pregnancies, all trisomy 21 pregnancies were identified (3 pregnancies) for a false-positive rate of 6.4%. Fβ-hCG and PAPP-A were significantly decreased in monochorionic pregnancies and PAPP-A was significantly decreased in pregnancies conceived by assisted reproduction. In the second study in 10 pregnancies one of the fetuses had a NT> 99th percentile, 5 DC (1.5%) and 5 MC (6.3%) with a normal karyotype. Among these, six structurally abnormalities were diagnosed (3 in dichorionics and 3 in monochorionics), and two intrauterine fetal demises occurred (1 in dichorionics and 1 in monochorionics). Normal perinatal outcome was observed in two pregnancies, one dichorionic and one monochorionic. Conclusion: The Combined Test maintains the detection rate achieved by NT screening for trisomy 21 in twin pregnancies, but false positive rates are reduced. The differences in the biochemical markers related to chorionicity or the mode of conception must be confirmed in further studies. NT>99th percentile with a normal karyotype was associated with a high rate of fetal abnormalities anf fetal demise irrespective of chorionicity KEY WORDS: Twin pregnancy; Combined Test; Down syndrome screening; first trimester screening; nuchal translucency; increased nuchal translucency; normal karyotype; fetal abnormalities; twin-twin transfusion syndrome