Abstract:

Plants are extremely plastic organisms with the ability to adapt and respond to the changing environmental conditions surrounding them. Sunlight is one of the main resources for plants, both as a primary energy source for photosynthesis and as a stimulus that regulates different aspects of their growth and development. UV-B comprises wavelengths that correspond to a high energy region of the solar spectrum capable of reaching the biosphere, influencing plant growth. It is currently believed that plants are able to acclimate when growing under the influence of this radiation and perceive it as a signal, without stress signs. Nonetheless, many UV-B induced changes are elicited after DNA damage occurs as a consequence of exposure. In this review we focus on the influence of UV-B on leaf, flower and root development and emphasize the limited understanding of the molecular mechanisms for most of this developmental processes affected by UV-B documented over the years of research in this area.

Author affiliation: Dotto, Marcela Claudia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Litoral. Facultad de Ciencias Agrarias; Argentina

Author affiliation: Casati, Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Centro de Estudios Fotosintéticos y Bioquímicos. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Centro de Estudios Fotosintéticos y Bioquímicos; Argentina

Abstract:

Los brassinosteroides (BRs)son hormonas vegetales esteroidales de reciente descubrimiento, amplia distribución en la naturaleza, y esenciales para el normal desarrollo de las plantas. En los últimos años se han multiplicado los estudios sobre sus propiedades biológicas y posibles aplicaciones agronómicas. Debido a su baja concentración en las fuentes naturales, los compuestos utilizados en estos estudios deben obtenerse mediante síntesis química a partir de precursores accesibles. El trabajo desarrollado en esta Tesis se ha centrado en la síntesis de 28-homobrassinosteroides, a partir de estigmasterol. Se han sintetizado quince BRs, cuatro de ellos habían sido detectados como compuestos naturales, y once son análogos nuevos con modificaciones en C-3, C-S y C-6. En particular, resultó de interés la síntesisde análogos fluorados, debido a las importantes propiedades biológicas conocidas para los compuestos organofluorados. Se evaluó la actividad biológica de cada uno de los compuestos sintetizados. Los bioensayos utilizados fueron inclinación de la lámina de arroz, elongación del epicotilo de soja y crecimiento de plántulas normales y mutantes de Arabidopsis thaliana.

Brassinosteroids (BRs) are a new group of recently discovered plant hormones, widely distributed in the plant kingdom. BRs are essential for the normal development of plants. During the last past years studies concerning their biological properties and possible use as agrochemicals have increased. Chemical syntheses of BRs are required since they cannot be obtained from natural sources, due to their extremely low concentrations. This work has been devoted to the synthesis of 28-homobrassinosteroids, using stigmasterol as starting material. Four out of the fifteen obtained compounds had already been identified as natural products. The other eleven synthetic BRs were new analogues, with modifications involving the C-3, C-5 and C6. The synthesis of fluorinated analogues was of particular interest, due to the important previously reported bioactivities of organofluorinated compounds. Biological activity for each synthetic compounds has been evaluated using the following bioassays: the rice lamina inclination test, the soybean epicotyl elongation and the growth of wild type and mutant seedlings of Arabi dopsis thaliana.

Author affiliation: Ramirez, Javier Alberto. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Abstract:

Dado el escaso conocimiento existente sobre las proteínas TCP de clase I, el objetivo general de esta tesis fue realizar un estudio funcional de ciertos miembros de esta subfamilia de factores de transcripción, a fin de revelar su participación en la regulación del desarrollo vegetal. Para ello, los objetivos específicos fueron los siguientes: 1) Estudiar los cambios morfológicos y de desarrollo ocasionados al expresar en plantas de A. thaliana las proteínas AtTCP11, AtTCP15 y AtTCP16 en su forma nativa o fusionadas a un dominio represor; 2) Identificar genes cuya expresión esté regulada directa o indirectamente por las proteínas en estudio; 3) Identificar posibles genes blanco de estas proteínas; 4) Estudiar los patrones de expresión conferidos por las regiones promotoras de los genes que codifican las proteínas bajo estudio. Los resultados obtenidos demuestran que los factores de transcripción TCP de clase I estudiados en el presente trabajo están involucrados en un gran número de procesos, especialmente relacionados con el desarrollo de órganos secundarios. Este trabajo de tesis aporta información relevante sobre las funciones de tres proteínas TCP de clase I de A. thaliana, ampliando el conocimiento sobre esta subfamilia y generando nuevas bases para estudios posteriores.

Due to the small amount of information available about the role of class I TCP transcription factors, the general objective of this thesis was to carry out a functional study of some members of this sub-family, in order to analyze their participation in plant development. The specific objectives were: 1) To study the morphological and developmental changes caused by the expression of AtTCP11, AtTCP15 and AtTCP16, either in native or modified forms, in A. thaliana. 2) To identify genes directly or indirectly regulated by these proteins. 3) To identify possible target genes. 4) To study the expression patterns conferred by the promoter regions of the corresponding genes. Here, we show that the Class I TCP transcription factors studied during the present work are involved in many processes in A. thaliana, especially related to secondary organ growth and development. This thesis brings information about the functions of three Class I TCPs, providing new clues to understand the role of these proteins in plant development and establishing a basis for future studies.

AGENCIA NACIONAL DE PROMOCIÓN CIENTÍFICA Y TECNOLÓGICA CONSEJO NACIONAL DE INVESTIGACIONES CIENTIFICAS Y TECNOLÓGICAS UNIVERSIDAD NACIONAL DEL LITORAL

Abstract:

Plants that express a fusion of the Arabidopsis thaliana class I TCP transcription factor TCP16 to the EAR repressor domain develop several phenotypic alterations, including rounder leaves, short petioles and pedicels, and delayed elongation of sepals, petals and anthers. In addition, these plants develop lobed cotyledons and ectopic meristems. Ectopic meristems are formed on the adaxial side of cotyledon petioles and arise from a cleft that is formed at this site. Analysis of the expression of reporter genes indicated that meristem genes are reactivated at the site of emergence of ectopic meristems, located near the bifurcation of cotyledon veins. The plants also show increased transcript levels of the boundary-specific CUP-SHAPED COTYLEDON (CUC) genes. The results suggest that TCP16 is able to modulate the induction of meristematic programs and the differentiation state of plant cells.

Author affiliation: Uberti Manassero, Nora Graciela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Agrobiotecnología del Litoral. Universidad Nacional del Litoral. Instituto de Agrobiotecnología del Litoral; Argentina

Author affiliation: Coscueta, Ezequiel Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Agrobiotecnología del Litoral. Universidad Nacional del Litoral. Instituto de Agrobiotecnología del Litoral; Argentina

Author affiliation: Gonzalez, Daniel Hector. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Agrobiotecnología del Litoral. Universidad Nacional del Litoral. Instituto de Agrobiotecnología del Litoral; Argentina

Abstract:

(Table presented.). Summary: Subtilases (SBTs) are serine peptidases that are found in all three domains of life. As compared with homologs in other Eucarya, plant SBTs are more closely related to archaeal and bacterial SBTs, with which they share many biochemical and structural features. However, in the course of evolution, functional diversification led to the acquisition of novel, plant-specific functions, resulting in the present-day complexity of the plant SBT family. SBTs are much more numerous in plants than in any other organism, and include enzymes involved in general proteolysis as well as highly specific processing proteases. Most SBTs are targeted to the cell wall, where they contribute to the control of growth and development by regulating the properties of the cell wall and the activity of extracellular signaling molecules. Plant SBTs affect all stages of the life cycle as they contribute to embryogenesis, seed development and germination, cuticle formation and epidermal patterning, vascular development, programmed cell death, organ abscission, senescence, and plant responses to their biotic and abiotic environments. In this article we provide a comprehensive picture of SBT structure and function in plants.

Author affiliation: Schaller, Andreas. Universidad de Hohenheim; Alemania

Author affiliation: Stintzi, Annick. Universidad de Hohenheim; Alemania

Author affiliation: Rivas, Susana. Centre National de la Recherche Scientifique; Francia

Author affiliation: Serrano, Irene. Centre National de la Recherche Scientifique; Francia

Author affiliation: Chichkova, Nina V.. Moscow State University; Rusia

Author affiliation: Vartapetian, Andrey B.. Moscow State University; Rusia

Author affiliation: Martinez, Dana Ethel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Fisiología Vegetal. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Fisiología Vegetal; Argentina

Author affiliation: Guiamet, Juan José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Fisiología Vegetal. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Fisiología Vegetal; Argentina

Author affiliation: Sueldo, Daniela Jorgelina. University of Oxford; Reino Unido

Author affiliation: van der Hoorn, Renier A. L.. University of Oxford; Reino Unido

Author affiliation: Ramírez, Vicente. Heinrich‐Heine University; Alemania

Author affiliation: Vera, Pablo. Universidad Politécnica de Valencia; España. Consejo Superior de Investigaciones Científicas; España

Abstract:

The importance of soil humus in soil fertility has been well established many years ago. However, the knowledge about the whole mechanisms by which humic molecules in the rhizosphere improve plant growth remains partial and rather fragmentary. In this review we discuss the relationships between two main signaling pathway families that are affected by humic substances within the plant: one directly related to hormonal action and the other related to reactive oxygen species (ROS). In this sense, our aims are to try the integration of all these events in a more comprehensive model and underline some points in the model that remain unclear and deserve further research.

Author affiliation: García, Andrés Calderín. Universidade Federal Rural Do Rio de Janeiro; Brasil

Author affiliation: Olaetxea, Maite. Universidad de Navarra; España

Author affiliation: Santos, Leandro Azevedo. Universidade Federal Rural Do Rio de Janeiro;

Author affiliation: Mora, Maria Veronica. Universidad de Navarra; España. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Baigorri, Roberto. Universidad de Navarra; España

Author affiliation: Fuentes, Marta. Universidad de Navarra; España

Author affiliation: Zamarreño, Angel Maria. Universidad de Navarra; España

Author affiliation: Berbara, Ricardo Luis Louro. Universidade Federal Rural Do Rio de Janeiro; Brasil

Author affiliation: Garcia-mina, José María. Universidad de Navarra; España

Abstract:

Nitric oxide (NO), a gaseous, redox-active small molecule, is gradually becoming established as a central regulator of growth, development, immunity and environmental interactions in plants. A major route for the transfer of NO bioactivity is S-nitrosylation, the covalent attachment of an NO moiety to a protein cysteine thiol to form an S-nitrosothiol (SNO). This chemical transformation is rapidly emerging as a prototypic, redox-based post-translational modification integral to the life of plants. Here we review the myriad roles of NO and SNOs in plant biology and, where known, the molecular mechanisms underpining their activity.

Author affiliation: Yu, Manda. University of Edinburgh; Reino Unido

Author affiliation: Lamattina, Lorenzo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigaciones Biológicas; Argentina. Universidad Nacional de Mar del Plata; Argentina

Author affiliation: Spoel, Steven H.. University of Edinburgh; Reino Unido

Author affiliation: Loake, Gary J.. University of Edinburgh; Reino Unido

Abstract:

Increasing concentrations of carbon dioxide and heavy metals in soils through pollution are serious problems worldwide. In the present study, we investigated the impacts of elevated atmospheric CO2 and fly ash (FA)-amended soil on the physiological response (chlorophyll content, non-structural carbohydrates, oil and total proteins) of soybean [Glycine max (L.) Merrill] at three growth stages (vegetative, reproductive and maturity). An increase in plant growth and biomass was observed at elevated CO2 and for moderate concentrations of FA in amended soils in all development plant stages. In contrast to these results, a different response pattern was found for the chlorophyll content and non-structural carbohydrates in relation to the developmental stage, showing that even though in the vegetative growth stage the highest concentration of chlorophylls corresponded to elevated CO2 conditions. An opposite result was observed during the grain<br />filling stage (reduction of chlorophylls of 15 % at ambient CO2 conditions for the treatments 10, 15, and 25 % of FA), which probably is related with the distribution of nutrients at this stage. Regarding to oil and total protein content an increase was observed at elevated CO2 and high concentrations of FA in amended soils. Our findings demonstrate that elevated CO2 and FA-amended soils alter the physiological response of soybean affecting the crop quality.

Author affiliation: Rodriguez, Judith Hebelen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina

Author affiliation: Klumpp, Andreas. Universidad de Hohenheim. Instituto de Paisaje y Ecologia Vegetal. Especialidad En Ecologia Vegetal y Ecotoxicologia; Alemania

Author affiliation: Högy, Petra. Universidad de Hohenheim. Instituto de Paisaje y Ecologia Vegetal. Especialidad En Ecologia Vegetal y Ecotoxicologia; Alemania

Author affiliation: Fangmeier, Andreas. Universidad de Hohenheim. Instituto de Paisaje y Ecologia Vegetal. Especialidad En Ecologia Vegetal y Ecotoxicologia; Alemania

Author affiliation: Maestri, Damian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto Multidisciplinario de Biología Vegetal (p); Argentina

Author affiliation: Lamarque, Alicia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina

Author affiliation: Labuckas, Diana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina

Author affiliation: Pignata, María Luisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina

Abstract:

TEOSINTE BRANCHED1-CYCLOIDEA-PROLIFERATING CELL FACTOR1 (TCP) transcription factors participate in plant developmental processes associated with cell proliferation and growth. Most members of class I, one of the two classes that compose the family, have a conserved cysteine at position 20 (Cys-20) of the TCP DNA-binding and dimerization domain. We show that Arabidopsis (Arabidopsis thaliana) class I proteins with Cys-20 are sensitive to redox conditions, since their DNAbinding activity is inhibited after incubation with the oxidants diamide, oxidized glutathione, or hydrogen peroxide or with nitric oxide-producing agents. Inhibition can be reversed by treatment with the reductants dithiothreitol or reduced glutathione or by incubation with the thioredoxin/thioredoxin reductase system. Mutation of Cys-20 in the class I protein TCP15 abolished its redox sensitivity. Under oxidizing conditions, covalently linked dimers were formed, suggesting that inactivation is associated with the formation of intermolecular disulfide bonds. Inhibition of class I TCP protein activity was also observed in vivo, in yeast (Saccharomyces cerevisiae) cells expressing TCP proteins and in plants after treatment with redox agents. This inhibition was correlated with modifications in the expression of the downstream CUC1 gene in plants. Modeling studies indicated that Cys-20 is located at the dimer interface near the DNA-binding surface. This places this residue in the correct orientation for intermolecular disulfide bond formation and explains the sensitivity of DNA binding to the oxidation of Cys-20. The redox properties of Cys-20 and the observed effects of cellular redox agents both in vitro and in vivo suggest that class I TCP protein action is under redox control in plants.

Author affiliation: Viola, Ivana Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Agrobiotecnología del Litoral. Universidad Nacional del Litoral. Instituto de Agrobiotecnología del Litoral; Argentina

Author affiliation: Güttlein, Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Agrobiotecnología del Litoral. Universidad Nacional del Litoral. Instituto de Agrobiotecnología del Litoral; Argentina

Author affiliation: Gonzalez, Daniel Hector. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Agrobiotecnología del Litoral. Universidad Nacional del Litoral. Instituto de Agrobiotecnología del Litoral; Argentina

Abstract:

After its initial definition in 1999, the TCP family of transcription factors has become the focus of a multiplicity of studies related with plant development at the cellular, organ, and tissue levels. Evidence has accumulated indicating that TCP transcription factors are the main regulators of plant form and architecture and constitute a tool through which evolution shapes plant diversity. The TCP transcription factors act in a multiplicity of pathways related with cell proliferation and hormone responses. In recent years, the molecular pathways of TCP protein action and biochemical studies on their mode of interaction with DNA have begun to shed light on their mechanism of action. However, the available information is fragmented and a unifying view of TCP protein action is lacking, as well as detailed structural studies of the TCPDNA complex. Also important, the possible role of TCP proteins as integrators of plant developmental responses to the environment has deserved little attention. In this review, we summarize the current knowledge about the structure and functions of TCP transcription factors and analyze future perspectives for the study of the role of these proteins and their use to modify plant development.

Author affiliation: Uberti Manassero, Nora Graciela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Agrobiotecnología del Litoral. Universidad Nacional del Litoral. Instituto de Agrobiotecnología del Litoral; Argentina

Author affiliation: Viola, Ivana Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Agrobiotecnología del Litoral. Universidad Nacional del Litoral. Instituto de Agrobiotecnología del Litoral; Argentina

Author affiliation: Welchen, Elina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Agrobiotecnología del Litoral. Universidad Nacional del Litoral. Instituto de Agrobiotecnología del Litoral; Argentina

Author affiliation: Gonzalez, Daniel Hector. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Agrobiotecnología del Litoral. Universidad Nacional del Litoral. Instituto de Agrobiotecnología del Litoral; Argentina