ABSTRACT Boron toxicity is a severe abiotic stress affecting plant growth and productivity in semi-arid regions of the world including Anatolian plateau. In this study, we investigated antioxidative responses of cotton (Gossypium hirsutum L.) as well as four different B transporter and aquaporin gene activities, which are early B stress responders, by using miR408 overexpression strategy. miR408 is a conserved microRNA in plant kingdom involved in almost all physiological responses of the plants as well as responses under abiotic and biotic stresses. Our results showed that, miR408 overexpression improved overall antioxidative status of cotton plants under B stress, in terms of reduced ion leakage and malondialdehyde levels and increased proline, chlorophyll and relative water contents. We also detected strong B transporter BOR1, BOR2 and water channel PIP1;1 and PIP2;1 gene expression in cotton leaf tissues under almost all treatments. miR408 overexpressing plants exhibited differential gene expression patterns when compared to control plants, always increasing with stress duration, revealing direct or indirect regulation of the genes by miR408 under B toxicity. Our results showed that, miR408 overexpression can be used as a strategy to improve B toxicity tolerance of cotton plants to increase agricultural production or for phytoremediation purposes on B rich soils.

Resumen Introducción: La producción de hojarasca, la dinámica de nutrientes foliares y la descomposición son esenciales para mantener el ciclo de nutrientes, la fertilidad del suelo y la regulación del carbono en ecosistemas terrestres. Con diversos estudios que abordan estos procesos, su variación en los bosques secos tropicales (BSTs) permanece incierta, por su compleja interacción de factores bióticos y abióticos. Objetivo: Evaluar la caída de hojarasca, el retorno potencial de nutrientes y eficiencia de uso, y la variación en descomposición en un gradiente sucesional de un BST en Tolima, Colombia. Métodos: Cuantificamos la caída de hojarasca entre noviembre 2017 y octubre 2019 en 12 parcelas distribuidas en cuatro estados sucesionales: bosque inicial, temprano, intermedio y tardío. Identificamos las especies arbóreas clave en la producción de hojarasca y caracterizamos la descomposición foliar de estas especies. A nivel comunitario, cuantificamos el retorno potencial de C, N y P, la eficiencia de uso de N y P y la relación C:N y N:P. Posteriormente, analizamos las relaciones entre las características de la vegetación y algunas propiedades químicas del suelo con estos procesos ecológicos. Resultados: Encontramos que la caída total de hojarasca en los bosques tardíos (8.46 Mg ha-1 año-1) fue el doble de la hallada en bosques iniciales (4.45 Mg ha-1 año-1). La descomposición fue mayor en bosques iniciales (k = 1.28) en comparación con bosques intermedios (k = 0.97) y tardíos (k = 0.87). El retorno potencial de nutrientes no cambió con el avance de la sucesión vegetal, pero exhibió diferencias entre los sitios de estudio. El desarrollo estructural y la riqueza de especies favorecieron la caída de hojarasca, mientras que las condiciones químicas del suelo influyeron en el retorno de nutrientes y descomposición. Conclusiones: Los BSTs tienen la capacidad de recuperar la función ecosistémica de aporte de hojarasca fina, retorno y liberación de nutrientes después del cese de alteraciones antrópicas; sin embargo, la calidad del suelo es fundamental en el retorno y liberación de nutrientes.

Abstract Introduction: The litterfall production, foliar nutrient dynamics and decomposition are essential to maintain nutrient cycling, soil fertility, and carbon regulation in terrestrial ecosystems. With several studies addressing the variation of these processes, their dynamics in tropical dry forests (TDFs) remain unclear, due to its complex interaction of biotic and abiotic factors. Objective: To evaluate litterfall, nutrient potential return and use efficiency, and decomposition variation in a TDF successional gradient in Tolima, Colombia. Methods: We quantified litterfall from November 2017 to October 2019 in 12 plots distributed in four successional stages: initial, early, intermediate, and late forests. We identified key tree species in foliar litter production and characterized the foliar decomposition of these species. At the community level, we quantified the C, N and P potential return, the N and P use efficiency, and the C:N and N:P ratio. Subsequently, we analyze relationships between vegetation characteristics and some soil chemical properties with these ecological processes. Results: We found that total litterfall in late forests (8.46 Mg ha-1 y-1) was double that found in initial forests (4.45 Mg ha-1 y-1). Decomposition was higher in initial (k = 1.28) compared to intermediate (k = 0.97) and late forests (k = 0.87). The nutrient potential return didn't change along succession, but it did show differences between study sites. The structural development and species richness favored litterfall, while soil chemical conditions influenced nutrient returns and decomposition. Conclusions: TDFs could recover key ecosystem function related to litterfall and nutrient dynamics after disturbances cessation; however, the soil quality is fundamental in return and release of nutrients.

Abstract NAC transcription factors are plant-specific proteins involved in many processes during the plant life cycle and responses to biotic and abiotic stresses. Previous studies have shown that stress-induced OsNAC5 from rice (Oryza sativa L.) is up-regulated by senescence and might be involved in control of iron (Fe) and zinc (Zn) concentrations in rice seeds. Aiming a better understanding of the role of OsNAC5 in rice plants, we investigated a mutant line carrying a T-DNA insertion in the promoter of OsNAC5, which resulted in enhanced expression of the transcription factor. Plants with OsNAC5 enhanced expression were shorter at the seedling stage and had reduced yield at maturity. In addition, we evaluated the expression level of OsNAC6, which is co-expressed with OsNAC5, and found that enhanced expression of OsNAC5 leads to increased expression of OsNAC6, suggesting that OsNAC5 might regulate OsNAC6 expression. Ionomic analysis of leaves and seeds from the OsNAC5 enhanced expression line revealed lower Fe and Zn concentrations in leaves and higher Fe concentrations in seeds than in WT plants, further suggesting that OsNAC5 may be involved in regulating the ionome in rice plants. Our work shows that fine-tuning of transcription factors is key when aiming at crop improvement. plantspecific specific stresses stressinduced stress induced OsNAC Oryza L. L upregulated up regulated (Fe (Zn plants TDNA T DNA factor maturity addition coexpressed co expressed finetuning fine tuning improvement

Abstract Terpenes produced by plants comprise a diverse range of secondary metabolites, including volatile organic compounds (VOCs). Terpene VOC production may be altered after damage or by biological stimuli such as bacterial, fungal and insects, and subsequent triggering of plant defense responses. These VOCs originate in plants from two independent pathways: the mevalonate and the methylerythritol phosphate pathways, which utilize dimethylallyl and isopentenyl diphosphates to form the terpenoidal precursors. Phakopsora pachyrhizi fungi causes Asian soybean rust, limiting soybean production and resulting in losses of up to 80% if no control strategies are applied. By using a transcriptome datasets, we investigated the regulation of genes of the mevalonate pathway under different biotic stresses. We studied the impact of P. pachyrhizi infection in vivo expression profile of genes involved in terpenoid and glyceollin biosynthesis in genotypes harboring different resistance genes (Rpp), and across the infection cycle. In addition, we used UPLC and UPGC analysis to evaluate glyceollin and VOC production, respectively, to identify metabolites associated with soybean responses to pathogen infection. The regulation of soybean genes involved in terpene production was influenced by genotypes, depending on the Rpp gene, while glyceollin was induced in all genotypes. Furthermore, a sesquiterpene was identified as a potential marker associated with rust symptoms on soybean.

Abstract Plant hormones are signaling molecules that are localized in different plant tissues and in specific amounts according to the process that they regulate. Changes in the concentration and distribution of plant hormones modulate the development and responses to biotic and abiotic stress. Autophagy, which means self-digestion, is a mechanism that degrades damaged or toxic components that arise from the metabolism, in order to recycle them and maintain the health of the cell. The most studied type of autophagy is macroautophagy which will be referred in this review as autophagy. In this process, double membrane vesicles called autophagosomes are formed to enclose damaged or unwanted cell cargo, which is later deposited for its degradation into the vacuole, from where the cell recovers amino acids, lipids and proteins. Indeed, communication between plant hormones and autophagy has been observed during development and growth, senescence and programmed cell death. In this review we discuss the advances in the understanding of the role of plant hormones involved in the modulation of autophagy in plants.

Resumen Las hormonas vegetales son moléculas señalizadoras que se localizan en los diferentes tejidos de una planta y en cantidades específicas de acuerdo al proceso que regulan. Los cambios en la concentración y distribución de las hormonas vegetales modulan el desarrollo y las respuestas al estrés biótico y abiótico. La autofagia, que significa autodigestión, es un mecanismo que degrada los componentes dañados o tóxicos que surgen del metabolismo, con la finalidad de reciclarlos y mantener la salud de la célula. En este proceso se forman vesículas de doble membrana llamadas autofagosomas, las cuales encierran la carga dañada o no deseada, que posteriormente se deposita para su degradación en la vacuola de donde la célula recupera aminoácidos, lípidos y proteínas. Se ha observado una confluencia entre las hormonas vegetales y la autofagia durante el desarrollo y el crecimiento, la senescencia y la muerte celular programada. En esta revisión repasamos los avances en la comprensión del papel de las hormonas vegetales involucradas en la modulación de la autofagia en las plantas.

Abstract WRKY transcription factors (TFs) are responsible for the regulation of genes responsive to many plant growth and developmental cues, as well as to biotic and abiotic stresses. The modulation of gene expression by WRKY proteins primarily occurs by DNA binding at specific cis-regulatory elements, the W-box elements, which are short sequences located in the promoter region of certain genes. In addition, their action can occur through interaction with other TFs and the cellular transcription machinery. The current genome sequences available reveal a relatively large number of WRKY genes, reaching hundreds of copies. Recently, functional genomics studies in model plants have enabled the identification of function and mechanism of action of several WRKY TFs in plants. This review addresses the more recent studies in plants regarding the function of WRKY TFs in both model and crop plants for coping with environmental challenges, including a wide variety of abiotic and biotic stresses.

The goal of the present work is to synthesize the process of collective construction developed to protect the high-altitude wetlands of the Blanco River basin, located in the Andes Mountains, Province of Mendoza. The participatory process arose out of an initiative of basin residents and users, and was conducted by the Integrative Committee for Creation of Potrerillos Municipal Environmental Protected Area (MEPA), composed of civil society organizations, government agencies and scientific institutions. The major pressures affecting the wetlands, identified through participatory assessment of the socio-ecosystem are: water pollution, reduction and total loss of habitat, stoppage of groundwater flows, artificial drainage, poldering of the meadow, and fragmentation of the wetland system, among other pressures. In order to identify priority sites for conservation of the ecosystem services (ES) wetlands provide, local people identified and prioritized the six most important of them, according to their perception: water for human consumption, agriculture and industry, aesthetic, spiritual and non-use representations, recreation and ecotourism, erosion control, water regulation and regulation of the biotic environment. The areas supplying ES were identified on the map of land use and land cover of the basin, with the wetland area, with tourist use and water catchment, and the watershed’s headwaters standing out as areas with higher ES provision. This process culminated in the creation of a protected area to halt the intense degradation afecting the wetland system, promoting maintenance of the natural area and improving its provision of ES. This collective process allowed integrating local and scientific knowledge, becoming an experience to be replicated in other areas in terms of conservation and land management. Among its major strengths is a strong coordination between the different social actors involved, which allowed success in reaching the implementation stage of a public policy for conservation.

El objetivo del presente trabajo consiste en sintetizar el proceso de construcción colectiva desarrollado con el fin de proteger los humedales de altura pertenecientes a la cuenca del Río Blanco de Potrerillos, localizados en la Cordillera de Los Andes, Provincia de Mendoza. El proceso participativo surgió ante una iniciativa de los pobladores locales y usuarios de la cuenca, y fue conducido por la Comisión Integradora para la Creación del Área Ambiental Protegida Municipal (AAMP) Potrerillos, integrada por organizaciones de la sociedad civil, instituciones gubernamentales y organismos científicos. Las principales presiones que afectan al humedal, identificadas a través del diagnóstico participativo del socio-ecosistema son: contaminación del agua, reducción y pérdida total de hábitat, corte del flujo de alimentación, drenaje artificial, polderización definitiva de vegas, fragmentación del sistema hidrológico, entre otras. A fin de determinar los sitios prioritarios para la conservación de servicios ecosistémicos (SE) que brinda el Sistema de humedales, la población local identificó y priorizó los seis más importantes de acuerdo a su percepción: agua para consumo humano, agricultura e industria; representaciones estéticas, espirituales y de no uso; recreación y ecoturismo; regulación de la erosión; regulación del ciclo hídrico y del ambiente biótico. Sobre el mapa de uso y cobertura de la tierra de la cuenca, fueron identificadas sus zonas proveedoras, destacándose el área de humedales con uso turístico y captación de agua, y las cabeceras de cuencas hídricas como las zonas con mayor provisión de SE. Este proceso culminó con la creación de un área natural protegida para detener el proceso de degradación intensiva que afecta al humedal, lo cual promueve el mantenimiento y la mejora de sus SE. Este proceso colectivo permitió integrar saberes locales con conocimiento científico, y se constituyó como una experiencia a replicar en otros territorios en el plano de la conservación y del ordenamiento territorial. Entre sus principales fortalezas se destaca la articulación sólida entre los diferentes actores sociales involucrados, que permitió alcanzar con éxito la etapa de implementación de una política pública de conservación.

The strawberry (Fragaria x ananassa Duch.) is vegetatively propagated, being the diseases caused by systemic pathogens one of the most important phytosanitary problems. More than 30 virus and phytoplasma diseases have been reported in strawberry crops worldwide. Virus-free and phytoplasma-free plants are used to control these diseases, which must be complemented with the regulation of the populations of vector insects, which are responsible of disseminating these diseases. The purpose of this review is to provide updated description of the virus and aphid species found in strawberry crops in Argentina, as a contribution to take phytosanitary actions in order to minimize the damage caused by these biotic threats. The virus species reported in Argentina are Strawberry mild yellow edge virus, Strawberry mottle virus, and Strawberry crinkle virus and Strawberry polerovirus 1, being described in this work their taxonomic and epidemiologic aspects, and their reported vectors. The aphid species found in strawberry crops in Argentina are Aphis forbesi Weed, Aphis gossypii Glover, Chaetosiphon fragaefolii (Cockerell), Chaetosiphon minor (Forbes), Chaetosiphon thomasi Hille Ris Lambers, Macrosiphum euphorbiae (Thomas), and Myzus persicae (Sulzer). Chaetosiphon species have been reported as responsible for most of the strawberry virus transmissions.

La frutilla (Fragaria x ananassa Duch.) es propagada vegetativamente por lo cual las enfermedades causadas por patógenos sistémicos constituyen uno de los problemas sanitarios más importantes. Más de 30 enfermedades provocadas por virus, fitoplasmas y otros patógenos sistémicos han sido reportadas en frutilla en el mundo. En esta especie se han detectado numerosos áfidos transmisores de los virus colonizando el cultivo. Las plantas libres de virus son usadas en el control de estas enfermedades, lo cual debe ser complementado con la regulación de las poblaciones de los insectos vectores, que son los responsables de dichas enfermedades. El objetivo de esta revisión fue brindar información actualizada de las especies de virus y pulgones encontrados en el cultivo de frutilla en Argentina, como un aporte para definir acciones fitosanitarias tendientes a minimizar el daño producido por estas amenazas bióticas. Los virus detectados en frutilla en Argentina son Strawberry mild yellow edge virus, Strawberry mottle virus, Strawberry crinkle virus y Strawberry polerovirus 1, describiéndose en este trabajo sus aspectos taxonómicos, epidemiológicos y los vectores reportados. Las especies de áfidos detectadas en frutilla en Argentina son: Aphis forbesi Weed, Aphis gossypii Glover, Chaetosiphon fragaefolii (Cockerell), Chaetosiphon minor (Forbes), Chaetosiphon thomasi Hille Ris Lambers, Macrosiphum euphorbiae (Thomas) y Myzus persicae (Sulzer). Las especies de Chaetosiphon han sido reportadas como responsables de las mayores transmisiones de virus en frutilla.

RESUMO A produtividade florestal depende dos fatores ambientais e bióticos da estação onde a espécie florestal se encontra. A produtividade da estação florestal é geralmente avaliada com modelos empíricos aplicados a dados de inventário fornecendo previsões discretas. Enquanto o uso de modelos num SIG permite a construção de mapas de distribuição de produtividade da estação. Assim, o objetivo deste estudo foi desenvolver um índice de produtividade utilizando estatística multivariada e geoestatística acopladas ao SIG para obter um mapa de produtividade florestal. Para o efeito, selecionou-se uma área de estudo com floresta de regeneração natural de pinheiro bravo no centro de Portugal. Primeiramente, o índice de produtividade (PI) foi construído usando a Análise Fatorial das Correspondências (FCA) com um índice de qualidade de estação para a espécie e região (Sh25- modelo de índice de altura) e variáveis ambientais (declive e exposição). Depois, o mapa PI foi obtido por Krigagem multi-Gaussiana e usado como camada SIG para avaliar as áreas da espécie por classe de produtividade (p.e., baixa, intermedia e alta). No final, o método de controle da área foi aplicado para determinar o tamanho e o número de parcelas a serem estabelecidas por classe de produtividade. As parcelas de igual produtividade foram digitalizadas em SIG e organizadas segundo uma progressão de idades disponíveis regularmente para abate anual ao longo de 50 anos. A abordagem metodológica desenvolvida neste estudo provou ser útil na construção de mapas de produtividade florestal que são instrumentos fundamentais para apoiar a regulação da produção florestal.

ABSTRACT Productivity is very dependent on the environmental and biotic factors present at the site where the forest species of interest is present. Forest site productivity is usually assessed using empirical models applied to inventory data providing discrete predictions. While the use of GIS-based models enables building a site productivity distribution map. Therefore, the aim of this study was to derive a productivity index using multivariate statistics and coupled GIS-geostatistics to obtain a forest productivity map. To that end, a study area vastly covered by naturally regenerated forests of maritime pine in central Portugal was used. First, a productivity index (PI) was built based on Factorial Correspondence Analysis (FCA) by incorporating a classical site index for the species and region (Sh25 - height index model) and GIS-derived environmental variables (slope and aspect). After, the PI map was obtained by multi-Gaussian kriging and used as a GIS layer to evaluate maritime pine areas by productivity class (e.g., low, intermediate and high). In the end, the area control method was applied to assess the size and the number of compartments to establish by productivity class. The management compartments of equal productivity were digitized as GIS layer and organized in a temporal progression of stands’ age regularly available for cutting each year during a 50-year schedule. The methodological approach developed in this study proved that can be used to build forest productivity maps which are crucial tools to support forest production regulation.

Stenoma cecropia infesta las nuevas siembras del híbrido interespecífico (Elaeis oleifera x E. guineensis) de palma de aceite en la zona de Tumaco (Nariño). Sus infestaciones afectan grandes extensiones de palma y causan defoliaciones de importancia económica. Por tal motivo, el objetivo de este trabajo fue determinar los factores bióticos y abióticos que afectan las poblaciones de la plaga a través de muestreos secuenciales quincenales, siguiendo un sistema móvil de desplazamiento 2 x 2, que consistió en realizar un muestreo cada dos palmas y cada dos líneas, en una hectárea de palma de aceite, contabilizando el número de individuos vivos y muertos de S. cecropia presentes en la hoja 17 y 25 de cada palma evaluada. Los resultados indican que S. cecropia es atacada por una diversidad de depredadores, parasitoides y entomopatógenos. Entre los primeros se encuentran las arañas (Araneae), chinches (Reduviidae), avispas (Vespidae) y hormigas (Formicidae), destacándose el género Crematogaster. Se encontró que Brachymeria sp. y Rhysipolis sp., fueron los parasitoides más frecuentes. Estas especies requieren del néctar de plantas como: Melanthera aspera, Solanum quitoense, Emilia sonchifolia, Lantana camara, Cassia reticulata, Stachytarphetacayennensis y Urena lobata, para su alimentación. También se colectaron larvas de S. cecropia infectadas por el hongoIsaria sp. Al estimar el efecto de estos controladores biológicos sobre las poblaciones de S. cecropia, se encontró que la depredación de la hormiga Crematogaster sp., sobre larvas de S. cecropia fue de 42,0 %. El parasitismo causado porBrachymeria sp., a las pupas fue de 16,8 %, la mortalidad causada por Rhysipolis sp., sobre el estado larval fue de 3,5 % y el efecto de Isaria sp., fue de 1,5 %. Se concluye que estos controladores biológicos son importantes en la regulación de las poblaciones de S. cecropia en el cultivo de la palma de aceite en Colombia.

Stenoma cecropia infests new plantations of hybrid oil palm (Elaeis oleifera x E. guineensis) in Tumaco (Nariño). These infestations are causing defoliation of economic importance to the oil palm. For this reason, the aim of this study was to determine the biotic and abiotic factors affecting populations through fortnightly sequential sampling, following a 2 x 2 moving displacement system, which sampled every two palms and every other line in a one hectare oil palm plantation, counting the number of live and dead individuals present in the 17th and 25th S. cecropia leaves of each palm evaluated. Results indicate that S. cecropia is attacked by a variety of predators, parasitoids and entomopathogens. Among the former are the spiders (Araneae), bugs (Reduviidae), wasps (Vespidae), and ants (Formicidae), with Crematogaster being the most important. Among the parasitoids, Brachymeria sp. and Rhysipolis sp. were most abundant. These species require the nectar of plants such as Melanthera aspera, Solanum quitoense, Emilia sonchifolia, Lantana camera, Cassia reticulata, Stachytarpheta cayennensis and Urena lobata, for food until the adult stage. An entomopathogenic fungus was also detected infecting the larval stage and was identified as Isaria sp. Crematogaster sp. predation on larval stages of S. cecropia was estimated to be 42 %. Parasitism by Brachymeria sp. in pupal stages was 16.8 %, mortality caused by Rhysipolis sp. on larval stages was 3.5 % and mortality by Isaria sp. was 1.5 %. It is concluded that these biological control agents are important in the regulation of S. cecropia populations in oil palm plantations in Colombia.

ABSTRACT The avian embryo is a time-honored animal model for understanding vertebrate development. A key area of extensive study using bird embryos centers on developmental phenotypic plasticity of the cardio-respiratory system and how its normal development can be affected by abiotic factors such as temperature and oxygen availability. Through the investigation of the plasticity of development, we gain a better understanding of both the regulation of the developmental process and the embryo's capacity for self-repair. Additionally, experiments with abiotic and biotic stressors during development have helped delineate not just critical windows for avian cardio-respiratory development, but the general characteristics (e.g., timing and dose-dependence) of critical windows in all developing vertebrates. Avian embryos are useful in exploring fetal programming, in which early developmental experiences have implications (usually negative) later in life. The ability to experimentally manipulate the avian embryo without the interference of maternal behavior or physiology makes it particularly useful in future studies of fetal programming. The bird embryo is also a key participant in studies of transgenerational epigenetics, whether by egg provisioning or effects on the germline that are transmitted to the F1 generation (or beyond). Finally, the avian embryo is heavily exploited in toxicology, in which both toxicological testing of potential consumer products as well as the consequences of exposure to anthropogenic pollutants are routinely carried out in the avian embryo. The avian embryo thus proves useful on numerous experimental fronts as an animal model that is concurrently both of adequate complexity and sufficient simplicity for probing vertebrate cardio-respiratory development.

Environmental stresses caused by either abiotic or biotic factors greatly affect agriculture. As for soybean [Glycine max (L.) Merril], one of the most important crop species in the world, the situation is not different. In order to deal with these stresses, plants have evolved a variety of sophisticated molecular mechanisms, to which the transcriptional regulation of target-genes by transcription factors is crucial. Even though the involvement of several transcription factor families has been widely reported in stress response, there still is a lot to be uncovered, especially in soybean. Therefore, the objective of this study was to investigate the role of bHLH and trihelix-GT transcription factors in soybean responses to environmental stresses. Gene annotation, data mining for stress response, and phylogenetic analysis of members from both families are presented herein. At least 45 bHLH (from subgroup 25) and 63 trihelix-GT putative genes reside in the soybean genome. Among them, at least 14 bHLH and 11 trihelix-GT seem to be involved in responses to abiotic/biotic stresses. Phylogenetic analysis successfully clustered these with members from other plant species. Nevertheless, bHLH and trihelix-GT genes encompass almost three times more members in soybean than in Arabidopsis or rice, with many of these grouping into new clades with no apparent near orthologs in the other analyzed species. Our results represent an important step towards unraveling the functional roles of plant bHLH and trihelix-GT transcription factors in response to environmental cues.

Heat shock (HS) leads to the activation of molecular mechanisms, known as HS-response, that prevent damage and enhance survival under stress. Plants have a flexible and specialized network of Heat Shock Factors (HSFs), which are transcription factors that induce the expression of heat shock proteins. The present work aimed to identify and characterize the Glycine max HSF repertory in the Soybean Genome Project (GENOSOJA platform), comparing them with other legumes (Medicago truncatula and Lotus japonicus) in view of current knowledge of Arabidopsis thaliana. The HSF characterization in leguminous plants led to the identification of 25, 19 and 21 candidate ESTs in soybean, Lotus and Medicago, respectively. A search in the SuperSAGE libraries revealed 68 tags distributed in seven HSF gene types. From the total number of obtained tags, more than 70% were related to root tissues (water deficit stress libraries vs. controls), indicating their role in abiotic stress responses, since the root is the first tissue to sense and respond to abiotic stress. Moreover, as heat stress is related to the pressure of dryness, a higher HSF expression was expected at the water deficit libraries. On the other hand, expressive HSF candidates were obtained from the library inoculated with Asian Soybean Rust, inferring crosstalk among genes associated with abiotic and biotic stresses. Evolutionary relationships among sequences were consistent with different HSF classes and subclasses. Expression profiling indicated that regulation of specific genes is associated with the stage of plant development and also with stimuli from other abiotic stresses pointing to the maintenance of HSF expression at a basal level in soybean, favoring its activation under heat-stress conditions.

Los fragmentos de bosque están delimitados por bordes y rodeados de matriz circundante. La interacción entre estas comunidades disímiles en estructura y composición, se define como efecto de borde. Este fenómeno genera localmente cambios abióticos y bióticos alterando procesos ecosistémicos del suelo. Para determinar la existencia de este efecto sobre la descomposición de hojarasca y sus factores de control, se seleccionaron dos fragmentos de bosque nublado en la Sabana de Bogotá. En cada fragmento se trazaron transectos con longitud de 64 m en dirección oriente-interior y occidente-interior, donde se dispusieron en siete distancias desde el borde experimentos de descomposición de hojarasca con duración de 90 y 180 días. En cada transecto y distancias se estimaron el porcentaje de descomposición y humedad de hojarasca, densidad de vegetación, densidad de hongos anamorfos y relación carbono:nitrógeno. Se determinaron la distancia máxima del efecto de borde sobre la descomposición y su interacción con la orientación, distancia y factores reguladores. Se evidenció un efecto de la orientación cardinal del borde sobre la descomposición y sobre sus factores reguladores. En las zonas de borde oriental se presentó un efecto de borde marcado sobre la humedad de hojarasca hasta los 7 m y sobre la densidad de vegetación hasta los 30 m. En los fragmentos de bosque la descomposición fue regulada por la humedad y la relación C:N de la hojarasca. La poca penetración del borde sugiere efectos menores sobre el ciclaje de nutrientes, proporcionando un valor adicional a la conservación de fragmentos pequeños.

Forest fragments are physically delimited by edges and encircled by a surrounding matrix. The interaction between these communities dissimilar in structure and composition is defined as the edge effect. This occurrence generates local abiotic and biotic changes altering soil ecosystem processes. To determine the existence of the effect on leaf litter decomposition and its control factors, two fragments of cloud forest in the southwest region of the Bogotá Savannah were selected. Within each, two 64 m long transects were laid out bearing east and west from edge to center respectively, a leaf litter decomposition experiment of a 90 to 180 day duration was set up at seven distances measured from the starting point of each transect. The percentage of leaf litter moisture and decomposition, vegetation density, anamorphic fungi density and carbon:nitrogen ratio were estimated at each point. The maximum distance of the edge effect on the decomposition was determined, and the interaction between orientation, distance and the regulating factors of the decomposition process were ascertained. The results established an effect of the cardinal orientation of the edge on the decomposition and its regulating factors. Marked edge effects on leaf litter moisture extending up to 7 m and up to 30 m on vegetation density were displayedin Eastern border areas. In forest areas, decomposition was regulated by leaf litter moisture and its C:N ratio. The limited penetration of edge effect suggests minor effects regarding nutrient cycles and provides justification and additional value to the use of small fragments.

Transcription factors (TFs) are proteins able to specifically recognize DNA sequences in the regulatory regions of their target genes. They bind these specific sequences, an event that leads to the activation or repression of whole signal transduction pathways. In plants about 1500 TFs were informatically identified; identification was mainly based in the presence of DNA-binding domains in the translated sequences. They were classified in families and subfamilies according to several features, including the conservation of the DNA binding domain, the genes structures and the functions they exert. Among transcription factors, several seem to be potential powerful biotechnological tools to improve crops via obtaining transgenic plants. Assigned purposes include: yield improvements, abiotic and biotic stress tolerances, and a combination of them. None of them is up to date a product market, since from the gene discovery to the regulation process (which differs in each country) there is a long pipeline to run. Since a few years ago, our research group is devoted to the structural and functional characterization of sunflower transcription factors, especially those belonging to the HD-Zip family. Members of this family exhibit in their structure a homeodomain (HD) associated to a leucine zipper (LZ). This association is unique to plants, being these two domains common to transcription factors from several kingdoms. It was proposed by other authors, and also by us, that this unique association is probably due to specific plant responses as plant development, which depends on environmental conditions. In this work we show an overview and new insights of the sunflower HD-Zip proteins, demonstrating to be useful biotechnological tools to confer drought, salt, herbicide, and herbivory (e.g. insect) tolerance, and other abiotic and biotic tolerance to stressgenerating factors. Like other TFs, sunflower HD-Zip transcription factors confer a complex phenotype to transgenic plants due to a combination of different regulated pathways. It is likely that TFs become the choice for breeders in the near future due to the demonstrated efficiency in conferring desired traits to transgenic plants. Additionally, from the public perception standpoint, the over or ectopic expression of a plant gene should be more accepted than the use of molecules from foreign organisms.

Los factores de transcripción (FTs) son proteínas capaces de reconocer y unir en forma específica secuencias de ADN presentes en las regiones regulatorias de los genes que resultan ser sus blancos. Cuando los FTs unen estas secuencias se produce la activación o la represión, según el caso, de vías de transducción de señales completas. En plantas cuyo genoma se conoce se han identificado con la ayuda de herramientas informáticas y en base a la presencia de dominios conservados de unión a ADN unos 1500 FTs. Estos fueron clasificados en familias y subfamilias de acuerdo a una serie de características estructurales y funcionales. Algunos de estos FTs podrían convertirse en poderosas herramientas biotecnológicas para el mejoramiento de cultivos de interés agronómico vía transgénesis. Los usos posibles serían, entre otros, el aumento de los rendimientos y la tolerancia a distintos tipos de estrés tanto de origen abiótico como biológico. Sin embargo, ninguno de estos FTs es hasta ahora un producto de mercado y esto es debido a que desde el descubrimiento de la funcionalidad de un gen hasta llegar a los procesos de regulación de transgénicos, que varían en los diferentes países, existen muchas etapas y pruebas a realizar que toman su correspondiente tiempo. Nuestro grupo de investigación se dedica desde hace años a la caracterización funcional de FTs de girasol, especialmente a aquellos que pertenecen a la familia HD-Zip. Los FTs de esta familia se caracterizan por la presencia en su estructura de un homeodominio (HD) asociado a un cierre de leucinas (LZ, del inglés "leucine zipper"). Si bien estos dos dominios existen en FTs pertenecientes a organismos de otros reinos, la asociación de ambos en una única proteína es una particularidad del reino vegetal y por eso se ha postulado que este tipo de FTs intervendría en procesos o eventos exclusivos de las plantas como el desarrollo dependiente de las condiciones ambientales. En este trabajo se muestra un panorama general, así como algunos nuevos aspectos novedosos inherentes a las funciones de las proteínas HD-Zip de girasol. Estas proteínas presentan un potencial biotecnológico relevante para conferir a los cultivos tolerancia a estrés hídrico, altas concentraciones de sales, herbicidas, ataque de insectos y otros factores generadores de estrés. En forma similar a lo que sucede con otros FTs que se expresan como transgenes, las proteínas HD-Zip confieren fenotipos complejos. Estos fenotipos complejos se dan por laregulación positiva o negativa de varias vías de transducción de señales al unísono. Creemos que en un futuro cercano los FTs van a ser los transgenes de elección para los mejoradores ya que han demostrado ser muy eficientes para generar características deseables en plantas. Además, para la percepción pública sería más aceptable sobre-expresar un gen vegetal que introducir en las plantas un gen proveniente de otros reinos.