Cytoplasrnic male sterility (CMS) is a maternally inherited defect in the production of pollen, the male gamete of the flower. This sterility can be suppressed by nuclear Restorer of Fertility (Rf) genes that normally downregulate the expression of the CMS-associated novel mitochondrial gene. In Brassica napus, nap CMS and pol CMS are associated with related chimeric mitochondrial genes orf222 and orf224, respectively. CMS in both nap and pol is associated with a polar loss of locule development, loss of synchronous locule development and clumping of sporogenous tissue away from the tapetal cell layer, as well as secondary effects on petal and bud formation. In nap CMS, early accumulation of orf222 transcripts in the locule regions of developing anthers is associated with sterility, while the absence of orf222 transcripts from the locules is associated with fertility restoration. Accumulation of novel antisense transcripts of atp6 in a cell specific manner which matches that of sense transcripts of orf222 and atp6 in nap CMS anthers may be indicative of a post-transcriptional regulatory mechanism associated with CMS in flower buds. / Restoration of fertility in Brassica napus nap and pol CMS is associated with nuclearly encoded genes Rfn and Rfp, respectively. These restorers are very closely linked to one another, and may be allelic. Further efforts to isolate Rfp have narrowed the genomic region to approximately 105 kb of a syntenic region in Arabidopsis thaliana. Cosmid clones isolated from a library of Brassica rapa genomic DNA introgressed with Rfp have been successfully sorted into contigs through the application of the amplified fragment length polymorphism technique. The region to which Rfp is mapped is syntenic to a region of Arabidopsis DNA that is a duplication of a second location at the 23 megabase region of chromosome 1 of that genome. This region contains pentatricopeptide (PPR) motif-encoding genes that are highly related to other restorers of fertility of other species. By inference, Rfp from Brassica napus may encode PPR motifs. The PPR genes related to these previously characterized restorers of fertility are often found alongside the restorer genes existing as mini-clusters of several PPR-encoding genes. This is likely caused by selective pressure acting on PPR-encoding genes that resulted in diversification and multiplication of these genes. In addition, the PPR genes of this duplicated region are not syntenically located, whereas the non-PPR-encoding genes maintain their syntenic locations. The same is true for orthologous comparisons between Arabidopsis and other plant species. PPR genes are therefore malleable and capable of alteration in response to changing environmental pressures, such as the evolution of sterility inducing genes.

Thesis (Ph. D.)--University of Hawaii at Manoa, 1995. / Includes bibliographical references (leaves 136-152). / Microfiche. / xiv, 152 leaves, bound ill. 29 cm

Thesis (Ph. D.)--University of Adelaide, Dept. of Plant Science, 1994. / Includes bibliographical references (leaves 93-114).

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaf 119). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaf 119). Also available on the Internet.

Orientadores: Louis Bernard Klaczko, Galina Ananina / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-15T15:35:04Z (GMT). No. of bitstreams: 1 Batista_MarcosRobertoDias_D.pdf: 1499232 bytes, checksum: f14f9f280608caee726a8954c332d6b9 (MD5) Previous issue date: 2010 / Resumo: Nesta tese, estudamos uma questão básica e uma aplicada: os determinantes da variação geográfica e temporal do polimorfismo de inversões do segundo cromossomo em populações naturais de Drosophila mediopunctata; ainda, adaptamos a técnica para análise de politênicos de Drosophila para estudos em Cochliomyia hominivorax e assim elaboramos um mapa dos cromossomos politênicos desta praga da pecuária. Duas décadas depois de estudos anteriores, realizamos cinco novas coletas no Itatiaia e observamos inesperadas mudanças nas frequências dos arranjos mais comuns e em sua variação microgeográfica em relação àquelas antes descritas. No segundo cromossomo, o arranjo DA continua sendo o mais frequente, porém não detectamos mais uma correlação significativa com a altitude. Para os arranjos DS e DP, além de não haver mais correlações significativas com a altitude, suas frequências se mostram ainda mais baixas, principalmente no inverno. Entretanto, o ciclo sazonal observado para estas inversões se mantém. O arranjo DI aumentou sua frequência significativamente e agora mostra uma correlação positiva e significativa com a altitude. Estes resultados sugerem que, depois de duas décadas, houve mudanças ambientais incluindo alterações climáticas e provavelmente fatores bióticos que devem ter afetado a arquitetura genética das populações. Observamos uma diferenciação entre o padrão das frequências de inversões do cromossomo II de populações vizinhas de D. mediopunctata. As matas estudadas estão situadas em duas diferentes unidades geomorfológicas, que apresentam diferenças marcantes em relação ao solo, relevo, paisagem, vegetação e fauna. Nossos resultados sugerem que a diferenciação geográfica observada nas frequências de inversões pode ser resultado de uma adaptação local às diferenças florísticas e climáticas. Entretanto, outros marcadores genéticos devem ser pesquisados para analisar os efeitos da fragmentação florestal sobre as populações. Cochliomyia hominivorax, conhecida no Brasil como a mosca-da-bicheira, é considerada uma das principais moscas causadoras de miíases primária na região Neotropical. Apesar de um fotomapa preliminar de seus cromossomos politênicos ter sido publicado anteriormente, com resultados encorajadores, não havia um mapa dos cromossomos politênicos com boa resolução para a espécie. Desta forma, elaboramos um novo fotomapa dos cinco autossomos com uma resolução total de 1450 bandas / Abstract: In this thesis, we studied a basic and an applied issue: the determinants of geographical and temporal variation of the second chromosome inversion polymorphism in natural populations of Drosophila mediopunctata; and, adapting the squashing technique used for Drosophila to Cochliomyia hominivorax, we made a map of the polytene autosomes of this livestock pest. Two decades after previous studies, we carried out five collections in Itatiaia, RJ. We observed unexpected changes in the frequencies of the most common inversions of the second chromosome. The DA gene arrangement is still the most common, but we no longer detect a significant correlation between its frequency and altitude. Furthermore, the frequencies of DS and DP inversions became even lower, especially in winter; and didn't show a significant correlation with altitude. However, the previously observed seasonal cycle for these inversions is still present. DI frequency increased significantly, and it is now significantly positively correlated with altitude. These results suggest that, after two decades, there were modifications in the climate, but other variables - such as biotic factors -have also probably changed and may be correlated with the changes in the genetic architecture of the Itatiaia population. Furthermore, we report a differentiation between frequencies of inversions of the second chromosome in neighboring populations of D. mediopunctata. The forests studied are located over two geomorphologic units that have marked differences regarding landscape, topography, soil, vegetation, and fauna. Our results suggest that the observed geographical variation in the inversion frequencies may be a result of local adaptation to climate and floral and faunal changes. However, further analysis with other genetic markers must be performed to assess the possible effects of forest fragmentation on different populations. Cochliomyia hominivorax, the New World screwworm fly is one of the main flies causing primary myiasis in the Neotropical region. Although a preliminary photomap of the polytene chromosomes of C. hominivorax was previously published, a good resolution map of the polytene chromosomes was not available for this species. Here, we present a new photomap of the five autosomes of this species with a total resolution of 1450 bands / Doutorado / Genetica Animal e Evolução / Doutor em Genetica e Biologia Molecular

Orientadores: Anete Pereira de Souza, Antonio Augusto Franco Garcia / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Economia / Made available in DSpace on 2018-08-20T23:12:17Z (GMT). No. of bitstreams: 1 Souza_LiviaMourade_D.pdf: 2370923 bytes, checksum: b0c800b4425fab2c0c9fda9cbbb4798d (MD5) Previous issue date: 2012 / Resumo: A seringueira é uma espécie de cruzamento misto e com um longo ciclo de vida, o que dificulta a geração de linhagens endogâmicas e, por consequência, a construção e integração de mapas de ligação usando as metodologias convencionais. A exemplo do que tem sido feito em outras espécies vegetais que apresentam limitações para a obtenção de linhagens endogâmicas, os mapas genéticos existentes para seringueira foram construídos utilizando populações F1 (com diferentes tipos de segregação). A integração dos mapas obtidos para cada um dos genitores é possível com base em marcadores bi-parental, onde ambos os genitores são heterozigóticos podendo segregar nas proporções 1:1:1:1, 1:2:1 e 3:1 na progênie F1. Além disso, o uso de marcadores codominantes e multialélicos, como os microssatélites, acrescentam muito à construção do mapa, uma vez que permite a obtenção de estimativas de frequência de recombinação e da fase de ligação com um menor viés. Os microssatélites são marcadores moleculares consagrados, sendo eles a ferramenta de escolha no estudo de diversos organismos pela simplicidade de uso e de análise. Entretanto, para espécies que ainda não têm grande parte de seu genoma sequenciado, a obtenção de marcadores desse tipo passa pela necessidade de desenvolvimento via bibliotecas genômicas. Esse trabalho objetivou desenvolver, caracterizar e mapear microssatélites em Hevea brasiliensis para possibilitar estudos genético-moleculares da variação morfológica, identificação de regiões genômicas associadas a fenótipos de interesse, bem como análises genético-populacionais. Uma biblioteca genômica enriquecida em motivos repetitivos foi construída, a partir da qual foram desenvolvidos os microssatélites utilizados nesse trabalho. A utilização dos microssatélites de Hevea brasiliensis em amplificações heterólogas envolvendo seis espécies do gênero Hevea resultou em aproximadamente 98% de sucesso nas amplificações, sugerindo a existência de um complexo formado pelas diferentes espécies do gênero. Um mapa genético-molecular foi construído utilizando-se 284 marcadores microssatélites na análise de uma população segregante F1 com 270 indivíduos, a partir do cruzamento entre os genitores PB217 e PR255. Por meio da utilização do programa ONEMAP foi possível a construção de um mapa de ligação integrado que revelou 2840 cM de extensão, distribuídos em 23 grupos de ligação. O mapeamento de QTLs realizado utilizando metodologia de mapeamento por intervalo composto (CIM) detectou 24 QTLs para altura e circunferência das plantas entre as estações de verão e inverno. Este trabalho é pioneiro na construção de um mapa integrado para seringueira pelo fato dele ter sido construído unicamente com marcadores microssatélites, os quais são altamente informativos. Além disso, é também o primeiro estudo envolvendo análise de QTL para características relacionadas ao crescimento de plantas em seringueira, bem como é inédita a aplicação da metodologia CIM para população F1 segregante / Abstract: The rubber tree is an mixed crossing species with a long life cycle, which makes it difficult for the generation of inbred lines, and, therefore, the construction and integration of linkage maps by using conventional methodologies. Similar to what has been reported from other plant species that have limitations to obtain inbred lines, the genetic maps for rubber tree have been constructed by using F1 populations (with different types of segregation). The integration of maps obtained for each of the genitors is possible based on bi-parental markers, where both genitors are heterozygous, being able to segregate in ratios 1:1:1:1, 1:2:1 and 3:1 in the F1 progeny. Moreover, the use of co-dominant and multi-allele markers, such as microsatellites, adds a lot to the construction of maps, since it allows the obtainment of estimates of recombination frequency and linkage phase with less bias. The microsatellites are established molecular markers which are the tool of choice in the study of various organisms for their simplicity of use and analysis. Nevertheless, their application in species whose genomes have not yet been sequenced requires a prior development phase. The present study intended to develop, characterize and map microsatellites for the species Hevea brasiliensis so that initiatives concerning morphological variation, identification of genomic regions linked to phenotypes of interest, as well as population genetic analysis. A repetitive DNA-enriched library was constructed from which it was developed the microsatellites used in this work. The use of Hevea brasiliensis microsatellites for heterologous amplification in other six Hevea species was done with approximately 98% of success ratio, suggesting the existence of a complex formed by different species. A molecular genetic map was constructed using 284 microsatellite markers in the analysis of an F1 segregating population with 270 individuals from a cross between the parents PB217 and PR255. By using the program ONEMAP it was possible the construction of an integrated linkage map that revealed 2840 cm in length, divided into 23 linkage groups. The QTL mapping methodology was performed using composite interval mapping (CIM) and detected 24 QTLs for plant height and circumference between summer and winter. This work is a pioneer in building an integrated map for rubber because it was built only with microsatellite markers, which are highly informative. Furthermore, it is also the first one involving the analysis of QTL for characteristics related to the growth of rubber tree plants, as well as novel application of the CIM methodology for this type of population / Doutorado / Genetica Vegetal e Melhoramento / Doutor em Genetica e Biologia Molecular

The Medicago truncatula NIP gene is located on M. truncatula Linkage Group 1. Informative recombinants showed crossovers that localize the NIP gene between markers 146O17 and 23C16D. Marker 164N9 co-segregates with the NIP gene, and the location of marker 164N9 is between markers 146O17 and 23C16D. Based upon data from the Medicago genome sequencing project, a subset of the model legume Medicago truncatula bacterial artificial chromosomes (BACs) were used to create a physical map on the DNA in this genetic internal. BACs near the potential NIP gene location near marker 164N9 were identified, and used in experiments to predict the physical map by a BAC-by-BAC strategy. Using marker 164N9 as a center point, and chromosome walking outward, the physical map toward markers 146O17 and 23C16D was built. The chromosome walk consisted of a virtual walk, made with existing sequence of BACs from the Medicago genome project, hybridizations to filters containing BAC DNA, and PCR reactions to confirm that predicted overlapping BACs contained DNA that yielded similar PCR products. In addition, the primers which are made for physical mapping via PCR could be good genetic markers helpful in discovering the location of the NIP gene. As a result of efforts repotted here, gap in physical map between marker 164N9 and 146O17 was closed.

In response to compatible rhizobia, leguminous plants develop unique plant organs, root nodules, in which rhizobia fix nitrogen into ammonia. During nodule invasion, the rhizobia gain access to newly divided cells, the nodule primordia, in the root inner cortex through plant-derived cellulose tubes called infection threads. Infection threads begin in curled root hairs and bring rhizobia into the root crossing several cell layers in the process. Ultimately the rhizobia are deposited within nodule primordium cells through a process resembling endocytosis. Plant host mechanisms underlying the formation and regulation of the invasion process are not understood. To identify and clone plant genes required for nodule invasion, recent efforts have focused on Medicago truncatula. In a collaborative effort the nodulation defect in the lin (lumpy infections) mutant was characterized. From an EMS-mutagenized population of M. truncatula, two non-allelic mutants nip (numerous infections with polyphenolics) and sli (sluggish infections) were identified with defects in nodule invasion. Infection threads were found to proliferate abnormally in the nip mutant nodules with only very rare deposition of rhizobia within plant host cells. nip nodules were found to accumulate polyphenolic compounds, indicative of a host defense response. Interestingly, nip was also found to have defective lateral root elongation suggesting that NIP has a role in both nodule and lateral root development. NIP was found to map at the upper arm of chromosome 1. In sli, infection threads were observed to bring rhizobia from infection threads to newly divided nodule primordium cells in the roots inner cortex. Polyphenolic accumulation in sli nodule/bumps was found. Lateral roots in sli were found to be clustered at the top of the root, indicating that sli like nip may be defective in lateral root development.

No description available.