1,721,175 research outputs found
Effect of changes in cell cycle gene expression on tomato fruit development
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94177.pdf (Publisher’s version ) (Open Access)Radboud Universiteit Nijmegen, 07 september 2012Promotores : Angenent, G.C., Mariani, C. Co-promotor : Maagd, R.A. de184 p
Characterization of the MADS domain transcription factor family in Arabidopsis thaliana
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27433.pdf (Publisher’s version ) (Open Access)Gene regulation at the level of transcription is crucial for almost all biological processes in a cell or organism. Transcription factors are sequence-specific DNA-binding proteins that are capable of activating and/or repressing transcription. The genome of Arabidopsis thaliana, for instance, consists out of ~6% transcription factors, which can be divided into families. One such family is the large MADS domain family and its members have been shown to be involved in, e.g. flowering, flower and root development, and fruit development. This thesis dealt with the ambitious aim to identify and characterize the complete Arabidopsis MADS domain family of transcription factors. Different perspectives were taken to obtain a global overview of this important transcription factor family at the gene and protein level and it opens new avenues to a more Systems Biology way of understanding.RU Radboud Universiteit Nijmegen, 10 mei 2006Promotor : Angenent, G.C.201, X p
Functional characterization of MADS box transcription factors in Petunia hybrida
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60667.pdf (Publisher’s version ) (Open Access)Transcription factors play a central role in the regulation and integration of several developmental pathways in all organisms. MADS box proteins are, among transcription factors, key players in the regulation of flower induction, flower architecture and vegetative development and have been isolated and studied in many different plant species. Chapter 2 offers an overview of floral development in several species from which MADS box genes have been analyzed, their function in determining the diversity of floral organs and their role in the evolution of floral morphologies. The rest of the thesis focuses on MADS box transcription factors in Petunia hybrida. The isolation of new genes and their preliminary characterization is described in Chapter 3. Phylogenetic analysis, expression analysis and interaction patterns of all the family members are included in this study. Strategies such as overexpression, cosuppression and knockout via transposon insertion have been adopted for a more detailed functional analysis of a few MADS box genes, as described in Chapter 4. These genes have been selected on the basis of their sequences, expression and interaction patterns which altogether suggested possible roles in floral organ determination, flower induction and vegetative development. A thorough analysis of the genes belonging to the FBP2 subfamily follows in Chapter 5, where it is demonstrated that FBP2 is functionally equivalent to the Arabidopsis SEPALLATA (SEP) proteins on the basis of similarities in sequence, expression, interaction patterns, mutant phenotypes and the functional complementation of the Arabidopsis sep triple mutant with FBP2. In Chapter 6 the function of UNS is studied in detail, by sequence and expression analysis, and overexpression of a full-length and a truncated protein in both petunia and Arabidopsis plants. The function of UNS in petunia is similar to SUPPRESSOR OF OVEREXEPRESSION OF CONSTANS1 (SOC1), a promoter of flowering in Arabidopsis. A possible function of a MADS box complex including C-, D- and E-type proteins in bringing the flower meristem to an end, is proposed in Chapter 7. The hypothesis is supported by the phenotype of transgenic plants simultaneously overexpressing FBP2 and FBP11, which show an early arrest in development and a downregulation of TERMINATOR (TER), the petunia WUS homolog. An upregulation of the petunia C-type gene FBP6 and the D-type FBP7 and FBP11 is also observed. A positive feedback loop among C-, D-, and E- type genes is most likely occurring also within the flower. General considerations about the strategies adopted in this study, the relevance of such a research in the understanding of diversity and conservation in plant development, conclude this thesis.RU Radboud Universiteit Nijmegen, 24 november 2004Promotor : Angenent, G.C.190 p
Molecular characterization of the vernalization response in Lolium Perenne
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30028.pdf (Publisher’s version ) (Open Access)Control of flowering time in a wide variety of plant species is one of the most important developmental switches during plant development and depends on various environmental factors. In the past, the isolations of many flowering mutants in the model system Arabidopsis thaliana contributed to a better understanding of the regulation of flowering time. In this species four main promoting pathways were identified and among those, the vernalization pathway allows an acceleration of flowering induction in climatic areas with long periods of cold. The main objective of this thesis was to study and identify the genes involved in vernalization requirement in Lolium perenne, and compare the genetic control of prolonged cold exposure in Arabidopsis and this cereal species. Chapter 1 describes the process of promotion of flowering induced by the vernalization pathway in Arabidopsis and winter cereals. The current view on the molecular function of genes controlling the vernalization response in Arabidopsis and in winter cereals is presented. In Chapter 2 a comprehensive expression analysis of 1500 unique cDNA clones from Lolium perenne is described, in order to identify genes up- or down-regulated during the vernalization response.Chapter 3 reports the regulation of flowering time in vernalization- sensitive andinsensitive Lolium perenne accessions. In Chapter 5 a differential subtractive approach aiming at the isolation of a sub-set of genes that are responsive to vernalization in perennial ryegrass was followed. One of the identified genes, named LpLIR1 was initially a good candidate for a vernalization-related gene. Chapter 6 introduces the results obtained by the characterization of two MADS box genes involved in the regulation of flowering time in Arabidopsis by a new approach. In Chapter 7 a final discussion is presented in which once more the genetic control of vernalization in Arabidopsis and cereal species is compared.Radboud Universiteit Nijmegen, 22 mei 2007Promotor : Angenent, G.C. Co-promotor : Immink, R.G.H.147 p
MADS-box genes controlling inflorescence morphogenesis in sunflower
No full textMADS-box genes play an important role in plant ontogeny, particularly, in the regulation of floral organ induction and development. Eight full-length cDNAs of HAM genes (Helianthus annuus MADS) have been isolated from sunflower. They encode MADS-box transcription factors expressed in inflorescence tissues. In the frames of the ABCDE model, the HAM proteins were classified according to their structural homology to known MADS-box transcription factors. The HAM45 and HAM59 genes encode the homeotic C function and are involved in the control of the identity of pistil and stamens, while the HAM75 and HAM92 genes determine the A function and identity of floral and inflorescence meristems and petal identity. The HAM31, HAM2, HAM63, and HAM91 genes encode the B function and are involved in the formation of petals and stamens; and the HAM137 gene encodes the E function. Analysis of the expression of HAM genes in sunflower has demonstrated that the structural and functional differences between the ray and tubular flowers in the inflorescence could be a consequence of the lack of HAM59 expression during ray flower initiation
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
Functional and evolutionary studies of type I MADS box genes in Petunia hybrida and Arabidopsis thaliana
No full textMADS-box genes are very important for plant development and especially for the formation of the flower. The MADS box family of transcription factors in plants can be subdivided into two classes: the MIKC-type genes, which play essential roles in flower formation, and the type I genes, which are functionally poorly understood. In this thesis, functional and evolutionary aspects of the type I subfamily are elucidated and a thorough characterization of the Arabidopsis type I MADS box gene DIANA (AGL61) is presented. The research described in this thesis suggests that type I MADS box genes play important roles in female gametophyte development and especially in the process of double fertilization. In addition, the expression of several type I genes in the endosperm suggests that some genes play a role in this tissue as well. The importance of the type I genes for the double fertilization, a unique angiosperm feature, indicates that this subfamily of MADS box genes has been very important for angiosperm evolutio
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