O principal mecanismo de defesa das plantas frente a uma infecção viral é baseado no fenômeno chamado interferência por RNA (RNAi). Por meio da ação coordenada de proteínas como Argonautas, Dicers, RNA polimerases dependentes de RNA e proteínas de ligação a RNA de dupla fita (DRBs), o RNA viral é reconhecido e clivado a pequenos RNAs de interferência derivados de vírus (vsiRNAs). Os vsiRNAs, acoplados ao complexo proteíco de indução ao silenciamento, atuam sobre sequências de RNA ou DNA virais, podendo promover a clivagem, inibição da tradução ou metilação de seus alvos (para vírus de DNA). Neste trabalho foram realizados dois estudos que abordam mecanismos de defesa baseados em RNAi em plantas. No primeiro capítulo é descrito a integração do RNA1 do Cumcumber mosaic virus (CMV) no genoma de Glycine max. Através da análise de bibliotecas de sequenciamento de alta eficiência de RNA mensageiros (mRNAs), pequenos RNAs e DNAs de diferentes cultivares e diferentes tecidos de soja foi possível identificar que o evento de integração envolveu duas moléculas do RNA1 do CMV, o RNA de um retrotransposon e um mRNA de um gene endógeno. No locus aonde ocorreu esta integração as duas sequências do RNA1 estão em sentidos opostos. Os pequenos RNAs (sRNAs) das nossas bibliotecas alinham majoritariamente na região do RNA1 do CMV e são praticamente ausentes nas outras regiões da sequência integrada, sugerindo fortemente a formação de um grampo aonde hibridizam ambas as sequências do CMV. A presença desses sRNAs derivados do CMV em todos os tecidos estudados sugere uma provável função antiviral dessa sequencia que foi integrada em soja. No segundo capítulo, por microscopia confocal, foi estudada a interação entre as proteínas DRBs e o Potato virus X (PVX) durante a infecção viral em Nicotiana benthamiana. É demonstrado que as DRBs 2, 3 e 5 se realocam de sua posição original e se concentram em estruturas chamadas complexos de replicação viral durante a infecção por PVX. Esse fenômeno é um indicativo que essas proteínas podem estar atuando nos primeiros estágios de defesa da planta frente ao vírus. / The main defense mechanism of plants facing a viral infection is based on the phenomenon called RNA interference (RNAi). Through the coordinated action of proteins such as Argonaut, Dicers, RNA dependent RNA polymerases and double-stranded RNAbinding proteins (DRBs), the viral RNA is recognized and cleaved to virus-derived interfering small RNAs (vsiRNAs). The vsiRNAs, coupled to a protein complex that induce the silencing, act on DNA or RNA viral sequences promoting cleavage, translational inhibition or methylation of their targets (for DNA viruses). This work described two studies that address new defense mechanisms based on RNAi in plants. In the first chapter of this thesis is described the integration of the cucumber mosaic virus (CMV) RNA1 in the genome of Glycine max. Through the analysis of deep sequencing libraries of messenger RNA, small RNAs and DNA from different cultivars and different soybean tissues it was possible to identified that the integration event involved two molecules of CMV RNA1, the RNA of a retrotransposon and the mRNA of an endogenous gene. In the locus where the integration occurred the two RNA1 sequences are in opposite directions. Small RNAs (sRNAs) from our libraries mostly aligned in the region of CMV RNA1 and are practically absent in other regions of the integrated sequence, strongly suggesting the formation of a hairpin where both CMV sequences hybridize. The presence of these CMV-derived sRNAs in all surveyed tissues suggests a probable antiviral function for the sequence that was integrated into soybeans. In the second chapter, the interaction between the DRB proteins and the Potato virus X (PVX) during viral infection in Nicotiana benthamiana is assessed by confocal microscopy. It is shown that the DRBs 2, 3 and 5 relocate from its original position and concentrated in structures called viral replication complexes during infection by PVX. This is an indication that these proteins can act in the early stages of plant defense against the virus.

Thesis (Ph. D.)--University of Missouri-Columbia, 2007. / Includes bibliographical references. Also available in PDF format via the Internet.

No description available.

Thesis (Ph. D.)--University of Missouri-Columbia, 2008. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 4, 2009) Vita. Includes bibliographical references.

O principal mecanismo de defesa das plantas frente a uma infecção viral é baseado no fenômeno chamado interferência por RNA (RNAi). Por meio da ação coordenada de proteínas como Argonautas, Dicers, RNA polimerases dependentes de RNA e proteínas de ligação a RNA de dupla fita (DRBs), o RNA viral é reconhecido e clivado a pequenos RNAs de interferência derivados de vírus (vsiRNAs). Os vsiRNAs, acoplados ao complexo proteíco de indução ao silenciamento, atuam sobre sequências de RNA ou DNA virais, podendo promover a clivagem, inibição da tradução ou metilação de seus alvos (para vírus de DNA). Neste trabalho foram realizados dois estudos que abordam mecanismos de defesa baseados em RNAi em plantas. No primeiro capítulo é descrito a integração do RNA1 do Cumcumber mosaic virus (CMV) no genoma de Glycine max. Através da análise de bibliotecas de sequenciamento de alta eficiência de RNA mensageiros (mRNAs), pequenos RNAs e DNAs de diferentes cultivares e diferentes tecidos de soja foi possível identificar que o evento de integração envolveu duas moléculas do RNA1 do CMV, o RNA de um retrotransposon e um mRNA de um gene endógeno. No locus aonde ocorreu esta integração as duas sequências do RNA1 estão em sentidos opostos. Os pequenos RNAs (sRNAs) das nossas bibliotecas alinham majoritariamente na região do RNA1 do CMV e são praticamente ausentes nas outras regiões da sequência integrada, sugerindo fortemente a formação de um grampo aonde hibridizam ambas as sequências do CMV. A presença desses sRNAs derivados do CMV em todos os tecidos estudados sugere uma provável função antiviral dessa sequencia que foi integrada em soja. No segundo capítulo, por microscopia confocal, foi estudada a interação entre as proteínas DRBs e o Potato virus X (PVX) durante a infecção viral em Nicotiana benthamiana. É demonstrado que as DRBs 2, 3 e 5 se realocam de sua posição original e se concentram em estruturas chamadas complexos de replicação viral durante a infecção por PVX. Esse fenômeno é um indicativo que essas proteínas podem estar atuando nos primeiros estágios de defesa da planta frente ao vírus. / The main defense mechanism of plants facing a viral infection is based on the phenomenon called RNA interference (RNAi). Through the coordinated action of proteins such as Argonaut, Dicers, RNA dependent RNA polymerases and double-stranded RNAbinding proteins (DRBs), the viral RNA is recognized and cleaved to virus-derived interfering small RNAs (vsiRNAs). The vsiRNAs, coupled to a protein complex that induce the silencing, act on DNA or RNA viral sequences promoting cleavage, translational inhibition or methylation of their targets (for DNA viruses). This work described two studies that address new defense mechanisms based on RNAi in plants. In the first chapter of this thesis is described the integration of the cucumber mosaic virus (CMV) RNA1 in the genome of Glycine max. Through the analysis of deep sequencing libraries of messenger RNA, small RNAs and DNA from different cultivars and different soybean tissues it was possible to identified that the integration event involved two molecules of CMV RNA1, the RNA of a retrotransposon and the mRNA of an endogenous gene. In the locus where the integration occurred the two RNA1 sequences are in opposite directions. Small RNAs (sRNAs) from our libraries mostly aligned in the region of CMV RNA1 and are practically absent in other regions of the integrated sequence, strongly suggesting the formation of a hairpin where both CMV sequences hybridize. The presence of these CMV-derived sRNAs in all surveyed tissues suggests a probable antiviral function for the sequence that was integrated into soybeans. In the second chapter, the interaction between the DRB proteins and the Potato virus X (PVX) during viral infection in Nicotiana benthamiana is assessed by confocal microscopy. It is shown that the DRBs 2, 3 and 5 relocate from its original position and concentrated in structures called viral replication complexes during infection by PVX. This is an indication that these proteins can act in the early stages of plant defense against the virus.

O principal mecanismo de defesa das plantas frente a uma infecção viral é baseado no fenômeno chamado interferência por RNA (RNAi). Por meio da ação coordenada de proteínas como Argonautas, Dicers, RNA polimerases dependentes de RNA e proteínas de ligação a RNA de dupla fita (DRBs), o RNA viral é reconhecido e clivado a pequenos RNAs de interferência derivados de vírus (vsiRNAs). Os vsiRNAs, acoplados ao complexo proteíco de indução ao silenciamento, atuam sobre sequências de RNA ou DNA virais, podendo promover a clivagem, inibição da tradução ou metilação de seus alvos (para vírus de DNA). Neste trabalho foram realizados dois estudos que abordam mecanismos de defesa baseados em RNAi em plantas. No primeiro capítulo é descrito a integração do RNA1 do Cumcumber mosaic virus (CMV) no genoma de Glycine max. Através da análise de bibliotecas de sequenciamento de alta eficiência de RNA mensageiros (mRNAs), pequenos RNAs e DNAs de diferentes cultivares e diferentes tecidos de soja foi possível identificar que o evento de integração envolveu duas moléculas do RNA1 do CMV, o RNA de um retrotransposon e um mRNA de um gene endógeno. No locus aonde ocorreu esta integração as duas sequências do RNA1 estão em sentidos opostos. Os pequenos RNAs (sRNAs) das nossas bibliotecas alinham majoritariamente na região do RNA1 do CMV e são praticamente ausentes nas outras regiões da sequência integrada, sugerindo fortemente a formação de um grampo aonde hibridizam ambas as sequências do CMV. A presença desses sRNAs derivados do CMV em todos os tecidos estudados sugere uma provável função antiviral dessa sequencia que foi integrada em soja. No segundo capítulo, por microscopia confocal, foi estudada a interação entre as proteínas DRBs e o Potato virus X (PVX) durante a infecção viral em Nicotiana benthamiana. É demonstrado que as DRBs 2, 3 e 5 se realocam de sua posição original e se concentram em estruturas chamadas complexos de replicação viral durante a infecção por PVX. Esse fenômeno é um indicativo que essas proteínas podem estar atuando nos primeiros estágios de defesa da planta frente ao vírus. / The main defense mechanism of plants facing a viral infection is based on the phenomenon called RNA interference (RNAi). Through the coordinated action of proteins such as Argonaut, Dicers, RNA dependent RNA polymerases and double-stranded RNAbinding proteins (DRBs), the viral RNA is recognized and cleaved to virus-derived interfering small RNAs (vsiRNAs). The vsiRNAs, coupled to a protein complex that induce the silencing, act on DNA or RNA viral sequences promoting cleavage, translational inhibition or methylation of their targets (for DNA viruses). This work described two studies that address new defense mechanisms based on RNAi in plants. In the first chapter of this thesis is described the integration of the cucumber mosaic virus (CMV) RNA1 in the genome of Glycine max. Through the analysis of deep sequencing libraries of messenger RNA, small RNAs and DNA from different cultivars and different soybean tissues it was possible to identified that the integration event involved two molecules of CMV RNA1, the RNA of a retrotransposon and the mRNA of an endogenous gene. In the locus where the integration occurred the two RNA1 sequences are in opposite directions. Small RNAs (sRNAs) from our libraries mostly aligned in the region of CMV RNA1 and are practically absent in other regions of the integrated sequence, strongly suggesting the formation of a hairpin where both CMV sequences hybridize. The presence of these CMV-derived sRNAs in all surveyed tissues suggests a probable antiviral function for the sequence that was integrated into soybeans. In the second chapter, the interaction between the DRB proteins and the Potato virus X (PVX) during viral infection in Nicotiana benthamiana is assessed by confocal microscopy. It is shown that the DRBs 2, 3 and 5 relocate from its original position and concentrated in structures called viral replication complexes during infection by PVX. This is an indication that these proteins can act in the early stages of plant defense against the virus.

M.Tech. / The tobacco species Nicotiana tabacum has been cultivated in South Africa since 1657, South Africa is considered to be a major producer and exporter of tobacco worldwide. The chlorine percentage of the leaf is very important to cigarette manufacturers when purchasing tobacco from farmers, as a high chlorine percentage value affects the burning quality of the cigarette. The chlorine percentage of the leaves depends on many factors such as rainfall, fertilizer, soil content of chlorine and irrigation. If tobacco with a high chlorine content is not phased out, South African tobacco will lose its export value and the value of the farmers crop may decrease by up to 35%. The research study was undertaken to establish the effect of an isopathically prepared treatment, Chlorine 9CH, on the chlorine percentage levels of (growing) Nicotiana tabacum plants. The research was conducted on the farm J151 in Marble Hall, Mpumalanga from 15 November 2004 to 4 March 2005. Two groups each containing fifty plants were randomly chosen to serve as the Control and Experimental group. There was an initial control period of four weeks during which two Pre-tests were performed on ten plants in each group at two week intervals. The experimental component of the study took place over two months during which the Experimental group was treated with Chlorine 9CH via a knapsack and the Control group was treated with filtered water only via a knapsack sprayer. Both groups were treated twice daily. During the experimental component, two Post-tests were performed on ten plants from each group (at week 8 and week 12) and the third Post-test was performed on the cured leaves the final row of each group (at week 12 and week 14).

No description available.

Thesis (Ph. D.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (March 1, 2007) Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references (leaves 246-266). Also available on the Internet.