1,720,987 research outputs found
Control of lateral meristem formation in Antirrhinum majus
Full text linkPlant architecture is designed by shoot growth and branching developing from axillary meristem. Lateral meristem formation has been already studied in model plants, e.g. Arabidopsis thaliana, tomato, rice and maize (Wang and Li, 2008). The characterization of plant architecture mutants pinpointed that GRAS transcription factors LATERAL SUPPRESSOR regulate the initiation of axilary meristem (Schumacher et al., 1999; Greb et al., 2003). The Solanum lycopersicum lateral suppressor (ls) mutant and its orthologous in Arabidopsis thaliana las are unable to develop secondary meristems at the axil of leaves. Indeed, these mutants develop a single stem and do not form secondary inflorescences. In tomato ls flowers do not develop petals and are characterized by reduced female and male fertility.
Also in Antirrhinum majus LAS orthologous (named ERAMOSA/ERA) greatly contributes to design plant architecture. Here we show that eramosa mutant does not develop axillary meristem, whilst the apical meristem itself is bigger. Moreover era mutant forms very few flowers completely disorganized. Preliminary results suggest also that ERA is involved in the control of ovule number since the mutant presents less ovules respect to the wildtype. Differently from its orthologous in Arabidopsis and tomato, ERA is indeed likewise expressed in the ovule primordial
MATERNAL CONTROL OF SEED DEVELOPMENT: THE ROLE OF THE MADS-BOX GENES SEEDSTICK AND ARABIDOPSIS B SISTER.
Full text linkThe haploid generation of flowering plants develops within the sporophytic tissues of the ovule that protect the female gametophyte developing inside. After fertilization the maternal seed coat develops in a coordinated manner with the embryo and endosperm and undergoes several changes including accumulation of secondary metabolites such as proanthocyanidins and mucilage. The research performed in these three years had the goal to investigate the interaction between the two generations. In particular we have identified key factors, expressed in the seed integuments (maternal tissue) controlling several aspects of seed development.
In the arabidopsis bsister (abs) mutant the endothelium, does not accumulate proanthocyanidins and cells have an abnormal morphology (ref). ABS encode for a transcription factor belonging to MADS box family. Another MADS-box gene, SEEDSTICK regulates redundantly with SHATTERPROOF 1 (SHP1) and SHP2 ovule identity (ref). Here we describe the characterization of the abs stk double mutant. This double mutant develops very few seeds due to both a reduced number of fertilized ovules and seed abortions later during development. Morphological analysis revealed the total absence of the endothelium in this double mutant. Additionally, massive starch accumulation was observed in the embryo sac. The abs stk analysis strongly suggests a maternal role in the regulation of the fertilization process and highlights the importance of the endothelium for the development of the next generation. Here we also report new functions of the MADS-box transcription factor STK during seed development. stk mutant seeds present defect in seed coat morphology and abnormal proanthocyanidins accumulation. In addition, stk mutant seeds present problems in mucilage release. Our data reveal new functions of STK after fertilization highlighting the importance of this transcription factor indicated as a key regulator of seed development
The backstage of the ABC model: The Antirrhinum majus contribution
No full textAt the beginning of the 1990s, a simple genetic model that explained flower development was presented based on Arabidopsis thaliana and Antirrhinum majus floral homeotic mutants. According to this model, which is a milestone in plant development studies, flower development can be explained by three classes of genes (A, B and C), each one controlling the identity of organs in two adjacent whorls. Intriguingly, more than 20 years later, there are still some unanswered questions, in particular regarding the universality of the class A-function genes. Class A genes are well characterised in A. thaliana, but so far no A mutants have been described in other plant species nor in Antirrhinum majus. Here, we retrace the story that led to the proposal of the ABC model focusing on the contribution of A. majus to this model. Although fewer groups are still using A. majus as a model system, this plant was a master contributor to our comprehension of the molecular networks controlling flower developmen
The Dark Side of Fungi: How They Cause Diseases in Plants
Full text linkIf you have ever kept fruits, vegetables, or even bread in your kitchen for a long time, you have probably noticed the formation of a grayish and fuzzy covering over them. But what exactly are those grayish-white filaments? Are they dangerous for us? They are living things and they belong to the group of organisms called fungi. These fungi grow on other organisms, using them as a source of nourishment. In this article, we introduce fungi and describe how they can attack plants, fruits, and vegetables
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
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