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Germinação de sementes em resposta ao estresse salino e dormência das sementes: papéis dos hormônios e dos fatores de transcrição
Get PDFThe formation of a plant population depends on the plasticity of the germination of its seeds. This thesis aims to understand the mechanism of seed germination in response to salt stress and the role of transcription factors in germination. In chapter, it is reviewed the impact of climate change on seeds and the effect of hormonal balance in seeds. In addition, we present a brief review of the epigenetic effects on seeds and their impacts on plant adaptability, which can contribute to new perspectives. In the following chapters, we sought to investigate (i) the role of sodium and pH in hormonal balance during germination in Stylosanthes humilis. (ii) the role of transcription factors (TF) in dormancy and germination of Arabidopsis thaliana seeds. These studies were carried out in two independent experiments, which comprise chapters II and III presented here. In the second chapter, the following experiments were proceeded: seeds of S. humilis were incubated in a growth chamber. Ethylene, abscisic acid (ABA), 1-carboxylic acid-1-aminocyclopropane (ACC), ACC synthase (ACS) and ACC oxidase (ACO) and the primary metabolites were quantified. The results show that saline stress induces ABA synthesis independently of pH, leading to a reduction in the biosynthesis of ethylene, the main hormone involved in the germination of S. humilis. The third chapter aimed to understand how the transcription factor TEOSINTE BRANCHED1 CYCLOIDEA PROLIFERATING CELL FACTORS (TCP) family regulates the germination of Arabidopsis thaliana seeds. To help elucidate the functioning of the TCP8 and TCP14 genes, the TCP mutants were tested during seed germination. RNA- Sequencing data from seeds of TCP mutants were used to identify potential genes regulated by TCPs. The phenotype was evaluated and RT-qPCR (Real Time - quantitative PCR) were performed. In addition, transient gene expression analyses were performed on tobacco leaves. The results of this study show that TCP8 is a negative regulator of breaking dormancy in Arabidopsis thaliana. Together, these results suggest that TCP8 and TCP14 (both of class I TCPs) modulate the dormancy break in a contrasting manner. Thus, the role of TCP8 and TCP14 was demonstratedduring the germination of A. thaliana. Together, these data indicate the complexity of the germination process. Keywords: Germination. Dormancy. Seeds. Salt Stress. Stylosanthes humilis. Transcription factors. Arabidopsis thaliana.A formação de uma população de plantas depende da plasticidade da germinação de suas sementes. Esta tese tem como objetivo compreender o mecanismo de germinação de sementes em resposta ao estresse salino e o papel de fatores de transcrição na germinação. No capítulo I, é revisado o impacto das mudanças climáticas nas sementes e o efeito no equilíbrio hormonal. Além disso, fazemos uma breve revisão dos efeitos epigenéticos em sementes e seus impactos na adaptabilidade de plantas, o que pode contribuir para novas perspectivas. Nos capítulos seguintes, buscou-se investigar (i) o papel do sódio e do pH no equilíbrio hormonal durante a germinação de sementes de Stylosanthes humilis. (ii) O papel dos fatores de transcrição na dormência e germinação de sementes de Arabidopsis thaliana. Esses estudos foram realizados em dois experimentos independentes, que compõem os capítulos II e III aqui apresentados. No segundo capítulo, foram realizados os seguintes procedimentos: sementes de S. humilis foram incubadas em solução de NaCl e Na 2 CO 3 para a quantificação de etileno, ácido abscísico (ABA), ácido 1-carboxílico-1-aminociclopropano (ACC), ACC oxidase (ACO) e metabólitos primários. Os resultados mostram que o estresse salino induz a síntese de ABA de forma independente do pH, levando a redução na biossíntese do etileno, principal hormônio envolvido na germinação de S. humilis. O terceiro capítulo, teve como objetivo compreender como o fator de transcrição da família TEOSINTE BRANCHED1 CYCLOIDEA PROLIFERATING CELL FACTORS (TCP) regula a germinação de sementes de A. thaliana. Para ajudar a elucidar o funcionamento dos genes TCP8 e TCP14, mutantes TCP foram testados durante a germinação das sementes. Dados de sequenciamento de RNA de sementes de mutantes TCP foram usados para identificar os potenciais genes regulados por TCPs. O fenótipo foi avaliado e RT-qPCR (Real Time-quantitative PCR) foram realizados. Além disso, foram realizadas análises de expressão transiente de genes em folhas de tabaco. Os resultados deste estudo mostram que o TCP8 é um regulador negativo daquebra de dormência em A. thaliana. Juntos, esses resultados sugerem que o TCP8 e o TCP14 (ambos de TCPs de classe I) modulam a quebra de dormência de maneira contrastante. Assim, o papel do TCP8 e do TCP14 foi demonstrado durante a germinação de A. thaliana. Além disso, esses dados indicam o complexo processo de germinação. Palavras-chave: Germinação. Dormência. Stress salino. Stylosanthes humilis. Fatores de transcrição. Arabidopsis thaliana.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES
Induction of abscisic acid biosynthesis and its role in the ethylene metabolism associated with germination of Stylosanthes humilis H.B.K. seeds under salt stress
No full textO estabelecimento de uma população de plantas depende dos aspectos adaptativos da germinação de suas sementes. Em condições de laboratório, têm-se indicações de que a habilidade das sementes de Stylosanthes em produzir etileno confere tolerância ao estresse salino durante o processo de germinação. Até o momento, no entanto, as vias regulatórias que conectam o controle da biossíntese do etileno com a germinação das sementes sob condição de estresse salino não são, ainda, conhecidas. Assim, sementes de S. humilis foram escarificadas e transferidas para placas de Petri de vidro ou frascos Erlenmeyer e tratadas com solução de NaCl, ácido 1-carboxílico-1-aminociclopropano (ACC), fluridona e ácido abscísico (ABA), mantendo as no escuro, em câmara de crescimento. Quantificou-se a produção de etileno e ABA em cromatógrafo a gás e cromatografia líquida de ultra performance, respectivamente. Avaliou-se as ações integrativas entre o estresse salino e o metabolismo do etileno no controle da germinação de sementes de estilosante. Os resultados mostram que os efeitos inibitórios do NaCl sobre a germinação de sementes de S. humilis e a biossíntese de etileno foram revertidos por solução do ACC ou fluridona. Além disso, aumento na biossíntese do ABA foi observado quando as sementes foram tratadas com NaCl. Sob condição de estresse salino, as sementes também exibiram maiores níveis de aminoácidos e açúcares em relação ao controle (água desionizada). Entretanto, os níveis de ácidos orgânicos diminuíram em sementes tratadas com NaCl. Assim, o etileno parece ser essencial para acoplar o metabolismo primário ao processo de germinação das sementes de S. humilis sob condição de estresse salino. Esses resultados em conjunto indicam que o efeito do NaCl na germinação de sementes de S. humilis é uma consequência do aumento dos níveis de ABA promovida pela alta concentração de Na+, que induziu a inibição da biossíntese de etileno. Dessa forma, o ABA funcionaria como um sinal necessário para a sobrevivência das sementes de S. humilis sob condição de estresse salino.The establishment of a plant population depends on the adaptive aspects of the germination of its seeds. In laboratory conditions, there is evidence that the ability of Stylosanthes seeds to produce ethylene gives tolerance to salt stress during the germination process. Nowadays, however, regulatory pathways that control the ethylene biosynthesis with seed germination under salt stress conditions are not yet known. Thus, S. humilis (Townsville stylo) seeds were scarified and transferred to glass Petri dishes or Erlenmeyer flasks and treated with NaCl solution, 1-aminocyclopropane-1-carboxilic acid (ACC), fluridone and abscisic acid (ABA) solution, keeping in the dark, at a growth chamber. The production of ethylene and ABA in gas chromatograph and ultra- performance liquid chromatography were quantified, respectively. The integrative actions between saline stress and ethylene metabolism in the control of germination of Townsville stylo seeds were evaluated. The results showed that the inhibitory effects of NaCl on germination and ethylene biosynthesis of S. humilis seeds were reversed by ACC or fluridone solution. In addition, increase in ABA biosynthesis was observed when the seeds were treated with NaCl. Under salt stress condition, the seeds also exhibited higher levels of amino acids and sugars as compared with control (deionized water). However, organic acid levels decreased in seeds treated with NaCl. Thus, ethylene seems to be essential for coupling the primary metabolism to the germination process of S. humilis seeds under salt stress conditions. Together, these data indicate that effect of NaCl on S. humilis seed germination is a consequence of increased ABA levels promoted by high Na+ concentration, which induced inhibition of ethylene biosynthesis. Thus, the ABA would act as a necessary signal for the survival of S. humilis seeds under salt stress conditions.Fundação de Amparo à Pesquisa do Estado de Minas Gerai
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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