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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
161

Functional characterization of the mitochondrial adenine nucleotide transporter (ADNT1) in Arabidopsis thaliana under dark-induced senescence / Caracterização functional do transportador mitochondrial de nucleotídeos de adenina (ADNT1) em plantas de Arabidopsis thaliana submetidas à condição de senescência induzida pela escuridão

Pereira, Paula da Fonseca 28 February 2013 (has links)
Submitted by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2017-03-29T11:17:16Z No. of bitstreams: 1 texto completo.pdf: 905568 bytes, checksum: 94c53779a921ceebf36267e09ef933a1 (MD5) / Made available in DSpace on 2017-03-29T11:17:16Z (GMT). No. of bitstreams: 1 texto completo.pdf: 905568 bytes, checksum: 94c53779a921ceebf36267e09ef933a1 (MD5) Previous issue date: 2013-02-28 / Fundação de Amparo à Pesquisa do Estado de Minas Gerais / Ao contrário de outros transportadores de ADP/ATP, ADNT1 é o único que medeia um antiporte um de ATP preferencialmente por AMP, e, em menor grau, por ADP. Um trabalho prévio sugere que a expressão ADNT1 é maior em pontas de raízes e em tecidos senescentes. Considerando a elevada expressão de ADNT1 em tecidos senescentes, nos propusemos a investigar o papel do ADNT1 durante o processo de senescência induzida pelo escuro. Sob estas condições, plantas mutantes de Arabidopsis thaliana deficientes na expressão do transportador ADNT1 exibiram uma senescência antecipada em relação ao tipo selvagem, como evidenciado tanto pelo fenótipo visual das plantas após o crescimento em longos períodos de escuridão, como pela perda de clorofilas e da capacidade fotossintética. O tratamento prolongado de escuro levou, em geral, a um declínio mais rápido nos mutantes do que nos do tipo selvagem nos teores de clorofila e nos níveis de sacarose e de proteínas. Por outro lado, os níveis de aminoácidos totais e de alguns intermediários do ciclo TCA, como malato, fumarato e isocitrato geralmente aumentaram significativamente nos mutantes no final do tratamento de escuro. As razões NADH/NAD + e NADPH/NADP+ também se apresentaram maiores nos mutantes em comparação com o tipo selvagem, com a progressão da escuridão. Além disso, as plantas mutantes apresentaram sintomas de senescência precoce em comparação ao tipo selvagem, mesmo sob condições tidas como não estressantes. Estes dados demonstram, assim, que ADNT1 não é funcionalmente redundante aos previamente caracterizados transportadores de ADP/ATP, especialmente durante a falta de carbono, e reforçam a função potencial de ADNT1 no fornecimento da energia necessária para suportar o crescimento de tecidos vegetais heterotróficos. / Unlike other ADP/ATP carriers, ADNT1 is the only one that mediates an antiport of ATP, AMP, and, to a lesser extent, ADP and the corresponding deoxyadenine nucleotides. Previous work observed that ADNT1 expression is much stronger in root tips and senescing tissues. Considering the high expression of ADNT1 in senescing tissues, we have investigated the role of ADNT1 during the process of dark-induced senescence. Under these conditions, Arabidopsis thaliana mutants deficient in the expression of ADNT1 transporter displayed a similar, yet milder, early onset of senescence as evidenced both by the visual phenotype of plants following growth in extended periods of darkness and the loss of chlorophyll and photosynthetic competence. The extended dark treatment led in general to a more rapidly decline in the mutants than in the wild type in the levels of sucrose and protein. By contrast, the levels of total amino acids and TCA cycle intermediates malate, fumarate and isocitrate generally increased significantly in the mutants at the end of dark treatment. The NADH/NAD + and NADPH/NADP+ ratios also increased in mutants in comparison to the wild type with progression of the darkness. Additionally, the mutant plants exhibited symptoms of early senescence in comparison to the wild type even under optimal conditions. Altogether the data obtained demonstrate that ADNT1 is not functionally redundant to the previously characterized ADP/ATP carriers, especially during carbon starvation and reinforce the potential function for ADNT1 in the provision of energy which is required to support growth in heterotrophic plant tissues. / Não foi localizado o cpf do autor. Tese enviada pela secretaria do curso por e-mail, em 28-03-17.
162

Reconstituição da via de sinalização antiviral mediada por NIK1 de Arabidopsis em tomateiros / Reconstitution of the Arabidopsis NIK1-mediated antiviral signaling in tomato

Ávila, Larissa Gabriela Morais de 21 July 2017 (has links)
Submitted by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2018-04-19T17:29:27Z No. of bitstreams: 1 texto completo.pdf: 1046673 bytes, checksum: 303cdb874bd37b4e599895a7138301a8 (MD5) / Made available in DSpace on 2018-04-19T17:29:27Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1046673 bytes, checksum: 303cdb874bd37b4e599895a7138301a8 (MD5) Previous issue date: 2017-07-21 / Fundação de Amparo à Pesquisa do Estado de Minas Gerais / Recentemente, uma nova camada de defesa antiviral foi caracterizada em Arabidopsis thaliana, que é mediada pelo receptor NIK (NSP-Interacting Kinase) e protege a planta contra begomovirus. Quando a planta é infectada por um vírus, NIK1 oligomeriza com outro receptor imune ou com NIK1 para transfosforilar um ao outro e consequentemente, ativar o domínio cinase de NIK1. NIK1 é capaz de se ligar a proteína ribossomal L10 (RPL10), e é capaz de mediar sua fosforilação e subsequente translocação ao núcleo, onde RPL10 interage com LIMYB (L10-interacting Myb domain-containing protein) para regular negativamente a expressão de genes de proteínas ribossomais, levando a supressão global da tradução. Os mRNAs virais não são capazes de escapar ao mecanismo de regulação de tradução do hospedeiro, aumentando assim a resistência contra begomovirus. A proteína viral NSP interage com NIK1 e inibe sua atividade cinase, aumentando a patogenicidade do begomovírus em seu hospedeiro. Foi demonstrado em trabalhos anteriores que o mutante NIK1-T474D é um excelente alvo para engenharia genética, pois é constitutivamente ativada em linhagens transgênicas. Nesse trabalho, primeiramente foi realizado a reconstrução in silico da via de sinalização antiviral mediada por NIK1 em tomateiro, identificando possíveis componentes homólogos dessa via. Em seguida, foi examinada a possibilidade do duplo mutante T474D-T469A de conferir resistência contra begomovírus em linhagens transgênicas de tomateiro. Além disso, a linhagem transgênica NIK1-T474D-T469A foi transformada com o componente a jusante da via de sinalilzação antiviral, LIMYB de Arabidopsis, e examinamos o efeito da reconstituição dessa via de defesa durante a infecção viral. Os resultado dessa investigação indicam que a expressão de NIK1-T474D/T469A em linhagens transgênicas de tomateiro foi efetiva para suprimir a expressão de genes ribossomais, indicando que o duplo mutante é constitutivamente ativado em tomateiro. Além disso, a expressão de LIMYB em combinação com NIK1-T469A/T474D promoveu um efeito aditivo na repressão dos genes de proteínas ribossomais, possivelmente revelando uma melhorestratégia para obtenção de resistência a begomovírus. Para averiguar essa hipótese, as linhagens transgênicas foram desafiadas com os begomovírus de tomateiro ToYSV e ToSRV e a infecção foi monitorada por meio de sintomatologia e quantificação do DNA viral. Os resultados demonstraram que a expressão de NIK1-T469A/T474D em combinação com LIMYB é potencialmente um alvo melhor para modificar geneticamente genótipos suscetíveis. / Recently, a new layer of antiviral defenses was characterized in Arabidopsis thaliana, which is mediated by the immune receptor NIK (NSP-Interacting Kinase) and protects plants against begomoviruses. Upon virus infection, NIK1 oligomerizes with itself or another immune receptor to transphosphorylate one another and to activate the NIK1 kinase domain. Activated NIK1 mediates the phosphorylation of the ribosomal protein L10 (RPL10) and subsequent translocation to the nucleus, where RPL10 interacts with LIMYB (L10-interacting Myb domain-containing protein) to down-regulate the expression of ribosomal protein genes, leading to global translation suppression. The viral mRNAs are not able to escape this host translation regulatory mechanism enhancing host resistance against begomoviruses. The viral protein NSP interacts with NIK1 and inhibits its kinase activity, increasing the pathogenicity of begomoviruses by their hosts. We have previously demonstrated that the NIK1 mutant T474D is an excellent target for engineering begomovirus resistance because it is constitutively activated in transgenic lines. In this investigation, we first reconstructed in silico the NIK1-mediated antiviral signaling in tomato by identifying the tomato homologs of the components of the signaling pathway. Then, we examined the property of the double mutant T474D-T469A to confer resistance against begomoviruses in tomato transgenic lines. Furthermore, we overexpressed the downstream component of NIK1 antiviral signaling, LIMYB from Arabidopsis, in the T474D-T469A transgenic lines and examined the effect of reconstituting the antiviral pathway on begomovirus infection. Our results indicated that expression of T474D/T469A in transgenic lines was effective to suppress the expression of ribosomal protein genes, indicating that this double mutant is constitutively activated in tomato. Furthermore, expression of LIMYB in combination with T469A/T474D promoted an additive effect in ribosomal protein gene repression, possibly uncovering a better strategy to acquire begomovirus resistance. To examine this hypothesis, we challenged the transgenic lines with the tomato-infecting begomoviruses ToYSV and ToSRV and monitored the infection by symptomatology and quantitation of viral DNA.Our results demonstrated that expression of T469A/T474D in combination with LIMYB holds the potential to be a better target for engineering begomovirus resistance in susceptible genotypes. / Ficha catalográfica com erro: Morais de Ávila, Larissa Gabriela.
163

Superexpressão do gene dehidrina de Arachis duranensis em plantas transgênicas de Arabidopsis thaliana

Oliveira, Thaís Nicolini de 15 April 2016 (has links)
Dissertação (mestrado)—Universidade de Brasília, Departamento de Botânica, Programa de Pós-Graduação em Botânica, 2016. / Submitted by Nayara Silva (nayarasilva@bce.unb.br) on 2016-06-24T15:55:06Z No. of bitstreams: 1 2016_ThaísNicolinideOliveira.pdf: 2383809 bytes, checksum: 92976f3067a5cb3679dc9f4bedc9119f (MD5) / Approved for entry into archive by Raquel Viana(raquelviana@bce.unb.br) on 2016-07-07T21:13:20Z (GMT) No. of bitstreams: 1 2016_ThaísNicolinideOliveira.pdf: 2383809 bytes, checksum: 92976f3067a5cb3679dc9f4bedc9119f (MD5) / Made available in DSpace on 2016-07-07T21:13:20Z (GMT). No. of bitstreams: 1 2016_ThaísNicolinideOliveira.pdf: 2383809 bytes, checksum: 92976f3067a5cb3679dc9f4bedc9119f (MD5) / Espécies silvestres têm sido exploradas como fonte de alelos de tolerância para o melhoramento genético vegetal de várias culturas. O parental silvestre do amendoim, Arachis duranensis, é um genótipo que apresenta alta adaptabilidade ao déficit hídrico e foi utilizado em um ensaio de dry drown para sequenciamento do transcriptoma. A análise in silico e a validação por RT-qPCR de genes diferencialmente expressos auxiliaram na identificação de genes candidatos associados à resposta a seca. Dentre eles, uma proteína LEA mostrou-se positivamente regulada mediante a esse estresse. Sabe-se que proteínas LEA se comportam como chaperonas e são encontradas em abundância em tecidos sob dessecação, diante disso, o objetivo desse trabalho foi caracterizar, clonar e introduzir esse gene via transgenia em planta modelo (Arabidopsis thaliana) para compreender os efeitos da sua superexpressão. O gene foi inserido em plantas de A. thaliana, ecotipo Columbia 0, utilizando o método de floral dip e os eventos em homozigose (geração T3) foram testados. As linhagens foram plantadas em placas de meio MS com 150 mM de NaCl e 200 mM de manitol, separadamente, além de outro grupo que foi plantado em meio MS e colocado em temperaturas extremas (-18°C por uma hora e 37°C por oito horas). Foram calculadas as taxas de sobrevivência e o teor de açúcares solúveis totais de cada amostra/ensaio. O teste de seca também foi feito, onde a irrigação foi suspensa por 15 dias e foram feitas análises de área foliar, teor relativo de água e coexpressão de genes relacionados à tolerância a seca. Nos ensaios com NaCl e manitol não houveram diferenças entre as linhagens e as plantas não transformadas, além de ter sido observado desenvolvimento reduzido das plantas. Nos ensaios com temperaturas extremas as linhagens mantiveram seus teores de açúcares iguais ao controle enquanto as não-transformadas (NT) aumentaram seu teor de açúcares solúveis totais apenas no tratamento de calor e sem diferença significativa na taxa de sobrevivência entre as linhagens e NT. No ensaio com seca houve maior desenvolvimento da área foliar em algumas linhagens quando comparadas às plantas NT. Na análise de teor relativo de água as linhagens mostraram maiores teores relativos de água quando comparado à NT, sob condição de rega controlada e após 15 dias sem irrigação, sendo uma linhagem com maior teor significativo. Esse evento foi selecionado para a análise de expressão gênica de três genes coexpressos com a Dehidrina. Houve aumento da expressão dos três genes em diferentes situações, tanto pelo fato da planta superexpressar a AdDHN quanto pela indução da seca. Os resultados sugerem que esse gene possa conferir uma melhor resposta aos estresses abióticos. _________________________________________________________________________________________________ ABSTRACT / Wild species have been exploited as a source of tolerance alleles for plant breeding of various cultures. Arachis duranensis, a wild parental of the cultivated peanut, is a genotype which has high adaptability to drought and has been used in a dry down test for sequencing the transcriptome. In silico analysis and validation by RT-qPCR differentially expressed genes assisted in the identification of candidate genes associated with drought response. Among them, an LEA protein was positively regulated in response to this stress. It is known that LEA proteins behave as chaperones and are found in abundance in tissues under desiccation, therefore, the aim of this study was to characterize, clone and introduce this gene via genetic modification in the model plant Arabidopsis thaliana, to understand the effects of its overexpression. The gene was inserted into plants of A. thaliana, ecotype Columbia 0, using the floral dip method and homozygous lines (T3 generation) were assayed. The lines were sown on MS medium plates containing either 150 mM NaCl or 200mM mannitol, and another group that was grown in MS medium and placed at extremes temperatures (-18°C for one hour and 37°C for eight hours). Survival rates were calculated and the total soluble sugar content of each sample/test. The dry test was also done where irrigation was suspended for 15 days and analyses were made of leaf area, relative water content, and co-expression of genes related to drought tolerance. In assays with NaCl and mannitol, there were no differences between lines and non-transformed (NT) have been observed in addition to reduced development of plants. In assays with extreme temperatures, lines maintained their sugar content in levels equal to control while non-transformed (NT) increased their total soluble sugar content only under heat treatment, and no significant difference in survival rate between the lines and NT. In assay for drought, there was a greater leaf area development in some lines than in NT plants, while the relative water content analysis of the strains showed higher relative contents of water when compared to NT under controlled irrigation condition and after 15 days without irrigation, with one line showing a significant content. This line was selected for the gene expression analysis of ascorbate peroxidase, galactinol synthase and DREB. There was increased expression of the three genes in different situations, because the plant overexpresses the AdDHN and because the drought induction. The results suggest that AdDHN may give a better response to abiotic stresses.
164

Identifing Insulators in Arabidopsis thaliana

Gandorah, Batool January 2012 (has links)
In transgenic research the precise control of transgene expression is crucial in order to obtain transformed organisms with expected desirable traits. A broad range of transgenic plants use the constitutive cauliflower mosaic virus (CaMV) 35S promoter to drive expression of selectable marker genes. Due to its strong enhancer function, this promoter can disturb the specificity of nearby eukaryotic promoters. When inserted immediately downstream of the 35S promoter in transformation vectors, special DNA sequences called insulators can prevent the influence of the CaMV35S promoter/enhancer on adjacent tissue-specific promoters for the transgene. Insulators occur naturally in organisms such as yeasts and animals but few insulators have been found in plants. Therefore, the goal of this study is to identify DNA sequences with insulator activity in Arabidopsis thaliana. A random oligonucleotide library was designed as an initial step to obtain potential insulators capable of blocking enhancer-promoter interactions in transgenic plants. Fragments from this library with insulator activity were identified and re-cloned into pB31, in order to confirm their activity. To date, one insulator sequence (CLO I-3) has been identified as likely possessing enhancer-blocking activity. Also, two other oligonucleotide sequences (CLO II-10 and CLO III-78) may possess insulator activity but more sampling is needed to confirm their activity. Further studies are needed to validate the function of plant insulator(s) and characterize their associated proteins.
165

A Novel Non-coding RNA Regulates Drought Stress Tolerance in Arabidopsis thaliana

Albesher, Nour H. 05 1900 (has links)
Drought (soil water deficit) as a major adverse environmental condition can result in serious reduction in plant growth and crop production. Plants respond and adapt to drought stresses by triggering various signalling pathways leading to physiological, metabolic and developmental changes that may ultimately contribute to enhanced tolerance to the stress. Here, a novel non-coding RNA (ncRNA) involved in plant drought stress tolerance was identified. We showed that increasing the expression of this ncRNA led to enhanced sensitivity during seed germination and seedling growth to the phytohormone abscisic acid. The mutant seedlings are also more sensitive to osmotic stress inhibition of lateral root growth. Consistently, seedlings with enhanced expression of this ncRNA exhibited reduced transiprational water loss and were more drought-tolerant than the wild type. Future analyses of the mechanism for its role in drought tolerance may help us to understand how plant drought tolerance could be further regulated by this novel ncRNA.
166

Interakce giberelinů a cytokininů v růstu klíčních rostlin Arabidopsis thaliana

Horáková, Adéla January 2019 (has links)
Recently global warming and increasing environmental temperature are discussed very frequently. Ambient temperature is an important factor regulating plant growth and global changes in temperature could significantly affect the yield of the agriculture. Our previous work revealed the role of plant hormones cytokinins in response to temperature and showed cytokinins as negative regulators of the thermomorphogenesis. Since gibberellins are known as positive regulators of the thermomorphogenesis this work was focused on their interaction in response to temperature in Arabidopsis thaliana. Analysis of the morphology of plant seedlings showed that the effect of cytokinins dominates over gibberellins in response to high temperature and is detectable soon after high-temperature treatment. Analysis of gene expression showed that cytokinins induce expression of gibberellin biosynthesis enzyme GA20ox1 and decrease the expression of gibberellin degradation enzyme GA2ox6. On the other hand, cytokinins have an inhibitory effect on the expression of the master regulator of thermomorphogenesis PIF4. Analysis of transgenic line overexpressing PIF4 suggests that cytokinins could affect the thermomorphogenesis by regulation of the PIF4 expression but this process is not the key mechanism of the regulation of the response to high temperature.
167

Characterization of the role of MAP Kinases in stress induced responses

Siodmak, Anna E. 04 1900 (has links)
Biotic stresses such as infection by bacteria negatively affect plant growth and pose a severe threat to human food production. Improving our understanding of the immune systems of plants should help ensure food supplies in the years ahead. Bacterial infections induce Pattern-Triggered Immunity (PTI), a process in which plants perceive bacterial molecules and trigger an immune response. Mitogen- Activated Protein Kinase (MAPK) cascades are key players in this immunity process. Since the MAP Kinases (MPKs) 3/4/6 are mainly responsible for flg22- dependent phosphorylation events, we sought to find out how oxidation of MPK4 affects its ability to respond to stresses. Previous studies have shown varying kinase activity of MPK4 upon oxidation. Therefore, this project aims to provide an insight into the oxidative defense signaling mechanism of A. thaliana by investigating the role of MPK4 Cysteine181 in vitro and in vivo. Analysis of oxidation-mimicking as well as oxidation-dead mutants gave first hints that Cysteine181, which is located in the MPK4 substrate binding pocket, is a highly important regulatory residue of oxidative stress signaling by affecting MPK4 kinase activity and the activation of MPK3 and MPK6. Binding studies revealed that those events are due to sterical hindrance within the binding pocket of MPK4 and the blockage of upstream activator binding. The second part of this study characterizes compositional and post-translational changes of plant ribosomes during pathogen infection. Ribosomal proteins selectively participate in the formation of polysomes under different environmental and developmental conditions. However, the function of these changes still remains elusive. The current research project attempts to understand the plant ribosomal changes that occur upon exposure to bacterial pathogens. To observe ribosomal changes, A. thaliana plants were treated with a pathogen associated molecular pattern (PAMP), flg22. Mass spectrometric analysis identified quantitative changes of PAMP-induced ribosomal proteins in polysomes as well as changes in post-translational modifications. Spatial simulations of ribosomes revealed specific regions within the ribosomes to be PTI specific. This study demonstrates that MPK6 contributes to modification of P-stalk composition and phosphorylation status. The MPK6 mediated modifications may affect translation and in combination indicate a mechanism of PTI-related translational control.
168

Transposon dynamics in self- and cross-fertilizing plant populations

Wright, Stephen, 1975- January 2000 (has links)
No description available.
169

Thimet oligopeptidases TOP1 and TOP2 are essential regulators of defense priming and systemic acquired resistance in Arabidopsis thaliana

Nejat, Najmeh 06 August 2021 (has links) (PDF)
The effector-triggered immunity (ETI) is activated at the site of pathogen infection and results in a state of enhanced immunity called systemic acquired resistance (SAR) in distal, uninfected plant organs. SAR relays on mobile signals transported from infected cells to distal organs, and on signal amplification which supports transcriptional re-programming associated with priming and execution of SAR. Previous research in our lab has identified the chloroplastic TOP1 and cytosolic TOP2 as salicylic acid (SA)–binding oligopeptidases, non-competitively inhibited by SA. We demonstrate that SAR triggered with P. syringae DC3000 AvrRpt2 is abolished in top2 whereas top1 top2 exhibits a SAR slightly but consistently stronger than wild type (WT) controls, indicating that top1 is epistatic to top2. In agreement with the observed SAR phenotypes, top2 is defective in the induction of SAR markers including SA and Pip synthesis and SA signaling genes, whereas top1 top2 shows significantly higher induction of these markers. SAR- phenotype of top2 is rescued by exogenous SA, H2O2 and Pip applications. Interestingly, neither top1 nor top 1top2 are unable to mount SAR in response to Pip and H2O2 treatments. Analysis of ROS-responsive transcription factors and antioxidant gene induction in infected and distal tissues reveal significantly dysregulated patterns in all mutants, with top2 and top1 top2 most affected, indicating that TOP1 and TOP2 function together to support a pattern of successive waves of oxidation and reduction during SAR. The local and systemic oscillations are anti-corelated in Wt. The local vs. systemic anti-correlation is lost in the mutant genotypes. The amplitude of the mRNA oscillations is significantly lower in top2 plants, and significantly increased in top1top2 plants. top1 and top1top2 lost the oscillation compared to WT but they are still able to keep the expression up in time. top2 is unable to support the expression of some of the genes and oscillations and continued the expression of these genes in time. Overall, our results argue for a defining role of TOP chloroplastic and cytosolic proteolytic pathways in maintaining redox signaling necessary for the induction of SAR transcriptional re-programming and execution.
170

A study of IAA conjugate physiology in Arabidopsis thaliana

Campanella, James Joseph January 1996 (has links)
No description available.

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