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MADS-box genes expressed during flower development and fruit maturation in Nymphaea caerulea
Full text linkMADS-box genes have been found in all eukaryotes, but their number has greatly expanded in plants, where their functions range from root development to floral organ specification and to fruit development. During the development of flowers, some of them act as homeotic selector genes specifying the identity of the floral organs, according to the ABC(D)E model. The model was developed thanks to many studies carried out in eudicots and it works quite well to explain their flower development. By contrast, for many basal Angiosperms the same model does not fit equally well, because their flowers may be organized with a different architecture and their floral organs are not always similarly well defined. For instance, they may show transition forms for some of the floral components.
My PhD project studied MADS-box genes expressed in the developing reproductive structures of the basal Angiosperm Nymphaea caerulea.
The work has started with gene isolation, since no MADS-box sequence belonging to this species could be found in public databases. To isolate as many as possible MADS-box genes several starting samples and methods have been used. Overall, I was able to isolate the following different MADS-box genes from both flower and fruit tissues: APETALA1/FRUITFULL, APETALA3 (three splicing variants and two resulting proteins of different length), PISTILLATA, three different AGAMOUS-like genes (i.e. AG1, AG2, and AG3), SEPALLATA, AGL6, and JOINTLESS. Thus, genes belonging to all the functional classes of the canonical ABC(D)E model of flower development have been obtained and identified.
A detailed expression analysis of the isolated genes during flower and fruit development has revealed some interesting results. A complex scenario for the expressed MADS-box genes in floral developing tissues was obtained, which reflects the complex floral morphology of the water lily and is in accordance with previous studies conducted in basal Angiosperms’ flowers.
Considering that some MADS-box transcription factors involved in flower development are important also to regulate post-fertilization processes, I also studied in detail the N. caerulea fruit development, which appeared an interesting and finely tuned process.
The study of fruit maturation in a water lily represents the most novel aspect of this work. N. caerulea has a pluricarpellate ovary that after fertilization develops into a fleshy capsule. It matures underwater until its opening occurs to disperse a multitude of arillate seeds. Detailed observations of the fruit opening evidenced some specific zones involved in cell separation events like those that occur in the abscission zones of petioles and pedicels in terrestrial organs. Such interesting observations have been supported by the expression of genes involved in the determination (i.e. JNT) and in the activation (i.e. AG2) of these zones, but also by the presence of some cell wall degrading/modelling enzymes that may cause the separation events which trigger the fruit opening.
Finally, I noticed also that the actual seeds dispersion in this species is not carried out directly by its fleshy capsule, which almost completely dissolves in water shortly after its opening, rather by the soft arils that surround the seeds
New insights on the Xylaria species (Ascomycota, Xylariales) with bright-coloured exudates: Xylaria aurantiorubroguttata sp. nov. and revision of X. haemorrhoidalis and X. anisopleura type collections
Full text linkA new species of Xylaria is described based on morphological characters of both sexual and asexual morphs, and molecular data based on nuclear rDNA internal transcribed spacer, α-actin, β-tubulin and RNA polymerase subunit II sequences. Xylaria aurantiorubroguttata is characterized by the presence of both upright, cylindrical, long-stipitate and globose to subglobose, short-stipitate stromata, immature stromatal stages producing at first orange and then red drops, and ascospores with a slightly oblique, straight half spore-length germ slit. We provide also new morphological descriptions for X. haemorrhoidalis (holotype) and X. anisopleura (isosyntype), two Xylaria species belonging to X. polymorpha complex together with X. aurantiorubroguttata
MADS-box genes involved in the development of the reproductive structures of Nymphaea caerulea
No full textThe canonical ABC(D)E model is not suitable for the flower of the basal Angiosperm Nymphaea caerulea
No full textReproductive development in Trithuria submersa (Hydatellaceae: Nymphaeales): the involvement of AGAMOUS-like genes
Full text linkSpecies of Trithuria, the only genus of the family Hydatellaceae, represent ideal candidates to explore the biology and flower evolution of early diverging angiosperms. The life cycle of T. submersa is generally known, and the "reproductive units" are morphologically well described, but the availability of genetic and developmental data of T. submersa is still scarce. To fill this gap, a transcriptome analysis of the reproductive structures was performed and presented in this work. This analysis provided sequences of MADS-box transcription factors, a gene family known to be involved in flower and fruit development. In situ hybridization experiments on floral buds were performed to describe the spatiotemporal expression patterns of the AGAMOUS genes, revealing the existence of three AG genes with different expression domains in flower organs and in developing ovules. Trithuria may offer important clues to the evolution of reproductive function among early angiosperms and Nymphaeales in particular, and this study aims to broaden relevant knowledge regarding key genes of reproductive development in non-model angiosperms, shaping first flower appearance and evolution
In the basal Angiosperm Nymphaea caerulea the complexity of the reproductive structures is underlined by the MADS-box genes expressed during their development
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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
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