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SummaryClimate change alters relationships among environmental conditions and thus has the potential to change the selection pressures acting on adaptive gene variants. Using a landscape genomic approach, we show that the southern beech speciesNothofagus pumiliohas notable genetic adaptations to climate along its 2000-kilometer-long range in the Andes. We screened 47,336 SNP loci in 1,632 contigs and found that high-latitude sampling sites have lower genetic diversity, likely due to greater impact of glacial oscillations at high latitudes. Using four genome scan methods, we identified 457 outlier SNPs that are either strongly differentiated among subpopulations or associated with environmental covariates related to temperature, day length, and precipitation. Temperature and day length parameters were associated with notably more outliers than precipitation (n = 133, 113, and 61 outliers, respectively), and almost half of all annotated outliers were related to stress response (n=38, 21%) or catabolism-metabolism (n=43, 24%). Our findings suggest thatNothofagus pumiliois an ideal Andean model of genetic adaptation to climate change because it is locally adapted to extant climate conditions, and shifting patterns among environmental parameters may be detrimental to its future survival and adaptation potential.

Inflorescence movements in response to natural gradients of sunlight are frequently observed in the plant kingdom and are suggested to contribute to reproductive success. Although the physiological and molecular bases of light-mediated tropisms in vegetative organs have been thoroughly investigated, the mechanisms that control inflorescence orientation in response to light gradients under natural conditions are not well understood. In this work, we have used a combination of laboratory and field experiments to investigate light-mediated re-orientation of Arabidopsis thaliana inflorescences. We show that inflorescence phototropism is promoted by photons in the UV and blue spectral range (≤500 nm) and depends on multiple photoreceptor families. Experiments under controlled conditions show that UVR8 is the main photoreceptor mediating the phototropic response to narrowband UV-B radiation, and phototropins and cryptochromes control the response to narrowband blue light. Interestingly, whereas phototropins mediate bending in response to low irradiances of blue, cryptochromes are the principal photoreceptors acting at high irradiances. Moreover, phototropins negatively regulate the action of cryptochromes at high irradiances of blue light. Experiments under natural field conditions demonstrate that cryptochromes are the principal photoreceptors acting in the promotion of the heliotropic response of inflorescences under full sunlight. This article is protected by copyright. All rights reserved.

Seed germination is one of the earliest phenotypes expressed by plants, and the accuracy to germinate in the correct time and place is essential for plant population fitness. Cues that regulate germination have been exhaustively characterized in laboratory experiments. However, the way in which seed populations respond to these cues and the ecological meanings of this phenomenon are scarcely known. To help filling this gap, we studied the thermic regulation of seed germination and its link with local climatic characteristics in Festuca pallescens populations, an iconic perennial grass species of Patagonia. By coupling thermal time models with field and environmental data, we evaluated seed responsiveness to temperature during germination of nine Festuca pallescens populations distributed across their complete longitudinal range in North Patagonia. The idea behind this experimental design was to search for inter-population differences in early life traits relevant for recruitment of the species, and associate seed traits with local environmental characteristics. F. pallescens populations showed strong differences in seed sensitivity to temperature for the thermal regulation of the germination rate, described by the population mean thermal time for germination (θ(50)) and its standard deviation (σθ). The greatest values of θ(50) and σθ corresponded to populations inhabiting harsh environments. Moreover, θ(50) of the different populations showed strong correlations with their local thermal environmental parameters, indicating a relation between seed physiological traits and climate across the longitudinal gradient. We did not observe inter-population differences in the minimum temperature that allows germination (Tb = -0.47 ± 0.19 °C). Higher θ(50) and σθ in populations from harsh climates may constitute a strategy of the species to increase fitness in hostile habitats, preventing anticipated germination and promoting a slower seed bank depletion in regions where establishment is highly limited.

In the quest to understand how biotic interactions respond to climate change, one area that remains poorly explored is how interactions involving organisms other than vascular plants will respond. However the interactions between plants and biological soil crusts (BSCs) are relevant in many ecosystems and they will likely respond uniquely to climate change. Simultaneous considerations of both plant-plant and plant-BSC interactions may substantially improve our understanding of this topic. The aim of this study is to assess whether water availability differentially affects the biotic effects of BSCs and pioneer shrubs on the early life-history stage of tree seedling growth. We conducted a greenhouse factorial experiment with soil surface cover (bare soil, soil covered by a creeping shrub and BSC covered soil) and water regime (control and drought) as factors. We monitored Nothofagus pumilio (a native tree species of ecological and economic relevance) seedling water status and growth as well as changes in soil water content and soil properties. The shrub cover had a positive effect on soil water conservation and on the water balance of seedlings under water stress. However, its effect was negative for seedling growth under both water conditions. The BSC also contributed to soil water conservation and apparently added nutrients to the soil. The net effect of the BSC on seedling growth was negative under full-watering conditions but positive under water stress conditions. This result highlights how the studied biotic interactions, and especially interactions involving BSCs, depend on changes in water availability. Fil: Pissolito, Clara Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Recursos Naturales, Agroecología y Desarrollo Rural. - Universidad Nacional de Rio Negro. Instituto de Investigaciones en Recursos Naturales, Agroecología y Desarrollo Rural; Argentina Fil: Garibotti, Irene Adriana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Varela, Santiago Agustín. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche. Grupo de Ecología Forestal; Argentina Fil: Arana, Maria Veronica. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche. Instituto de Investigaciones Forestales y Agropecuarias Bariloche. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; Argentina Fil: Gonzalez Polo, Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Marchelli, Paula. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche. Instituto de Investigaciones Forestales y Agropecuarias Bariloche. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; Argentina Fil: Bruzzone, Octavio Augusto. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche. Instituto de Investigaciones Forestales y Agropecuarias Bariloche. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; Argentina

López, Aldana Soledad. Instituto Nacional de Tecnología Agropecuaria (INTA). Centro Regional Patagonia Norte. Estación Experimental Agropecuaria Bariloche (EEA Bariloche). Instituto de Investigaciones Forestales y Agropecuarias Bariloche (IFAB). Bariloche, Río Negro, Argentina. López, Aldana Soledad. CONICET - Instituto Nacional de Tecnología Agropecuaria (INTA). Centro Regional Patagonia Norte. Estación Experimental Agropecuaria Bariloche (EEA Bariloche). Instituto de Investigaciones Forestales y Agropecuarias Bariloche (IFAB). Bariloche, Río Negro, Argentina. López, Dardo Rubén. Instituto Nacional de Tecnología Agropecuaria (INTA). Centro Regional Córdoba. Estación Experimental Agropecuaria Manfredi (EEA Manfredi). Agencia De Extensión Rural Villa Dolores. Córdoba, Argentina. Arana, María Verónica. Instituto Nacional de Tecnología Agropecuaria (INTA). Centro Regional Patagonia Norte. Estación Experimental Agropecuaria Bariloche (EEA Bariloche). Instituto de Investigaciones Forestales y Agropecuarias Bariloche (IFAB). Bariloche, Río Negro, Argentina. Arana, María Verónica. CONICET - Instituto Nacional de Tecnología Agropecuaria (INTA). Centro Regional Patagonia Norte. Estación Experimental Agropecuaria Bariloche (EEA Bariloche). Instituto de Investigaciones Forestales y Agropecuarias Bariloche (IFAB). Bariloche, Río Negro, Argentina. Batlla, Diego. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura. Buenos Aires, Argentina. Marchelli, Paula. Instituto Nacional de Tecnología Agropecuaria (INTA). Centro Regional Patagonia Norte. Estación Experimental Agropecuaria Bariloche (EEA Bariloche). Instituto de Investigaciones Forestales y Agropecuarias Bariloche (IFAB). Bariloche, Río Negro, Argentina. Marchelli, Paula. CONICET - Instituto Nacional de Tecnología Agropecuaria (INTA). Centro Regional Patagonia Norte. Estación Experimental Agropecuaria Bariloche (EEA Bariloche). Instituto de Investigaciones Forestales y Agropecuarias Bariloche (IFAB). Bariloche, Río Negro, Argentina. Sensitivity to water availability is a key physiological trait for grassland species located in arid and semiarid environments, where successful germination is closely related to rainfall dynamics. Festuca pallescens inhabits diverse environments along a steep precipitation gradient in North Patagonia, thus ofering a suitable model for the study of germination behavior in response to water availability. \nBy analyzing germination in nine populations using a hydrotime model approach, we aimed to fnd within-species variation. Seed population behavior was analyzed under diferent hydric conditions using hydrotime model parameters (hydrotime, mean base water potential and its standard deviation). We estimated the mean base water potential for F. pallescens (micro b(50) = − 2.79 ± 0.45 MPa), which did not difer signifcantly between populations. However, the hydrotime parameter (θH) varied markedly, suggesting physiological adaptation to local environments. Higher values of H were found in populations located at the extremes of the distribution gradient, indicating that germination may be prevented or delayed in conditions that are suboptimal for the species. Since the variation in hydrotime model parameters did not follow a cline, micro-environmental cues may have the greatest infuence on the physiological behavior of the species, rather than the macroscale rainfall gradient. grafs., tbls.

Global warming is predicted to exert negative impacts on plant growth due to the damaging effect of high temperatures on plant physiology. Revealing the genetic architecture underlying the heat stress response is therefore crucial for the development of conservation strategies, and for breeding heat-resistant plant genotypes. Here we investigated the transcriptional changes induced by heat in Nothofagus pumilio, an emblematic tree species of the sub-Antarctic forests of South America. Through the performance of RNA-seq of leaves of plants exposed to 20°C (control) or 34°C (heat shock), we generated the first transcriptomic resource for the species. We also studied the changes in protein-coding transcripts expression in response to heat. We found 5,214 contigs differentially expressed between temperatures. The heat treatment resulted in a down-regulation of genes related to photosynthesis and carbon metabolism, whereas secondary metabolism, protein re-folding and response to stress were up-regulated. Moreover, several transcription factor families like WRKY or ERF were promoted by heat, alongside spliceosome machinery and hormone signaling pathways. Through a comparative analysis of gene regulation in response to heat in Arabidopsis thaliana, Populus tomentosa and N. pumilio we provide evidence of the existence of shared molecular features of heat stress responses across angiosperms, and identify genes of potential biotechnological application.

Planting native species requires particular genetic considerations in order to minimize the risks of maladaptation and genetic contamination. Outbreeding depression and genetic swamping are possible processes that should be avoided. Authenticity and functionality are two opposing objectives in active restoration of degraded ecosystems. Actual examples of genetic risks in Argentina regarding native species plantation are presented. Climate change is a deep conditioning of tree plantation, and according to the forecast for Argentina a future shifting in the natural range of forest tree species is expected. An example through ecological niche modeling in two Nothofagus species shows possible outcomes of this shift. Another example based on threshold models determining timing of germination describes possible altitudinal shifts. Assisted migration and assisted gene flow are potential resources to mitigate the impact of climate change: should we breed for the present or for the future climate? The dilemma of facing the risk of extinction through a risk of invasion.

High-throughput sequencing (HTS) technologies became a powerful approach to generate genomic resources in non-model tree species and to assist breeding programs. These technologies are being used in native forest trees of Argentina and this chapter summarizes the state-of-the-art knowledge. A brief description of the HTS technologies is followed by general applications of HTS on forest trees for genomic resources development and massive genotyping. Genomic strategies to accelerate tree breeding includes genome-wide association studies and genomic selection. HTS technologies were applied to Argentina’s native tree species for transcriptome and genome sequencing of Nothofagus species and transcriptome sequencing of Prosopis alba and Cedrela balansae. Ongoing HTS projects include the transcriptome sequencing of Austrocedrus chilensis, Handroanthus impetiginosus and Cordia trichotoma; the genome sequencing of Austrocedrus chilensis and the transcriptome sequencing of Nothofagus alpina and N. obliqua under drought stress conditions. Current and future genetic studies on native forest tree species and implications for breeding are discussed.

Rauli is an iconic species of the temperate sub-Antarctic forests due to its hardwood quality of pinkish tones. Because of its ecological and economic relevance, it is under conservation within national parks and being domesticated for plantation purposes. In this chapter, we present the state of the art of the species in Argentina. General features as distribution, biology and uses are firstly presented. Patterns of genetic variation at neutral markers allowed studying the legacy of the glacial ages as well as recent processes shaping the genetic structure. In addition, variation among populations at quantitative traits (phenological, physiological, morphological, architectural and growth rhythm traits) reflect the action of natural selection. Mycorrhizas and other soil fungi have strong relevance for conservation and domestication programmes, and their diversity is described. The domestication programme is dependent on seed productivity restrictions in natural stands, and the regulation of germination was studied through threshold models. The breeding strategy of rauli includes provenance and progeny tests, definition of genetic zones and seed collection areas based on genetic markers and installation of progeny seed orchards. Conservation and management of N. alpina forests in Argentina is finally discussed in the context of its over-exploitation in the past decades, conservation actions and management guidelines.

Trees are constantly exposed to climate fluctuations, which vary with both time and geographic location. Environmental changes that are outside of the physiological favorable range usually negatively affect plant performance and trigger responses to abiotic stress. Long-living trees in particular have evolved a wide spectrum of molecular mechanisms to coordinate growth and development under stressful conditions, thus minimizing fitness costs. The ongoing development of techniques directed at quantifying abiotic stress has significantly increased our knowledge of physiological responses in woody plants. However, it is only within recent years that advances in next-generation sequencing and biochemical approaches have enabled us to begin to understand the complexity of the molecular systems that underlie these responses. Here, we review recent progress in our understanding of the molecular bases of drought and temperature stresses in trees, with a focus on functional, transcriptomic, epigenetic, and population genomic studies. In addition, we highlight topics that will contribute to progress in our understanding of the plastic and adaptive responses of woody plants to drought and temperature in a context of global climate change., We review recent progress in our understanding of the molecular bases of drought and temperature stresses in trees, with a focus on functional, transcriptomic, epigenetic, and population genomic studies.

Context: Clinal genetic variation in natural populations could reflect either recent demographic history or the evolution of adapted genotypes along heterogeneous environments.Aims: We describe genetic variation patterns in three Nothofagus species of South American temperate forests, growing along steep rainfall gradients. Our hypothesis is that the selection pressure along this gradient reinforces the genetic structure previously shaped by Pleistocene climate oscillations. Methods: We screened variation along gradients at putative adaptive markers: candidate genes involved in response to drought, and EST-SSRs linked to drought stress genes. Genomic SSRs (gSSRs) were used to decouple the incidence of demographic events in the genetic structure.Results: Genetic diversity at SSRs agreed with the putative location of cryptic Pleistocene refugia in Nothofagus. In addition, each species showed different trends for nucleotide diversity at candidate genes. Unbiased heterozygosity significantly correlated with precipitation at EST-SSRs in N. nervosa. We found evidences of balancing selection and several SNPs departed from neutral expectations.Conclusions: Nothofagus genetic variability shows a strong imprint of demographic changes that reveals refugia location for the species during Pleistocene. This variability is modelled by environmental conditions across natural gradients, which impose selection pressure at genome regions related to stress response, providing clues about inter-specific differences in adaptive potential to water deficit. Fil: Soliani, Carolina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche. Instituto de Investigaciones Forestales y Agropecuarias Bariloche. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; Argentina Fil: Azpilicueta, María Marta. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche. Instituto de Investigaciones Forestales y Agropecuarias Bariloche. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; Argentina Fil: Arana, Maria Veronica. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche. Instituto de Investigaciones Forestales y Agropecuarias Bariloche. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; Argentina Fil: Marchelli, Paula. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche. Instituto de Investigaciones Forestales y Agropecuarias Bariloche. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; Argentina

Inflorescence stem movements in response to natural sunlight are widely spread across angiosperm species and are suggested to increase reproductive success. However, the underlying mechanisms that mediate this phototropic response to natural irradiation are unclear. We studied phototropic responses of Arabidopsis inflorescences in both laboratory and field conditions and report an action spectrum at wavelengths below 500 nm, mediated by several photoreceptor families. In controlled conditions, UVR8 is the key photoreceptor for narrowband UV-B radiation while phototropins and cryptochromes are crucial for phototropic responses to narrowband blue light. At low blue irradiances, phototropins are dominant while cryptochromes are essential during high blue irradiances but subjected to the negative control of phototropins. Importantly, cryptochromes are the principal photoreceptors mediating inflorescence stem bending under full sunlight.

Plant movements in response to directional solar radiation, known as “heliotropism” are frequently observed in nature. Although there is a considerable amount of literature on these movements in vegetative organs, knowledge about heliotropic responses in flowers and inflorescences is relatively limited. Here we comprehensively review studies on this topic, profile the diversity of responses encompassed under the term “heliotropism” and propose a conceptual framework for their classification. In addition, we discuss the mechanisms underlying different types of heliotropism in two species commonly used as model systems: Arabidopsis and sunflower. Finally, the ecological consequences of floral heliotropism are elaborated with an emphasis on the effects on plant reproductive success, and the potential agricultural implications of manipulating heliotropic responses are addressed as well. We conclude that inflorescence heliotropism appears conserved in many plant species that depend on pollinators, and consists of an auxin dependent response to solar radiation. Fil: Serrano, Alejandro Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentina Fil: Arana, Maria Veronica. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Vanhaelewyn, Lucas. University of Ghent; Bélgica Fil: Ballare, Carlos Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía; Argentina Fil: Van Der Straeten, Dominique. University of Ghent; Bélgica Fil: Vandenbussche, Filip. University of Ghent; Bélgica

Los servicios ecosistémicos que ofrecen los ecosistemas de humedales representan un beneficio para la sociedad. Se identificaron y analizaron los Servicios Ecosistémicos de los Humedales del río León en el Urabá Antioqueño en Colombia, una zona estratégica para el país en términos ecológicos y económicos. Se realizó una Valoración Económica del servicio Abastecimiento de agua para distintos usos. Se reconoció la relación directa entre los humedales y el agua subterránea. Se recomienda una gestión integral de los humedales, agua subterránea y bienestar humano., Facultad de Ingeniería

In the course of evolution, plants have developed mechanisms that orient their organs toward the incoming light. At the seedling stage, positive phototropism is mainly regulated by phototropin photoreceptors in blue and UV wavelengths. Contrasting with this, we report that UV RESISTANCE LOCUS8 (UVR8) serves as the predominant photoreceptor of UVB–induced phototropic responses in Arabidopsis (Arabidopsis thaliana) inflorescence stems. We examined the molecular mechanisms underlying this response and our findings support the Blaauw theory (Blaauw, 1919), suggesting rapid differential growth through unilateral photomorphogenic growth inhibition. UVR8-dependent UV-B light perception occurs mainly in the epidermis and cortex, but deeper tissues such as endodermis can also contribute. Within stems, a spatial difference of UVR8 signal causes a transcript and protein increase of transcription factors ELONGATED HYPOCOTYL5 (HY5) and its homolog HY5 HOMOLOG at the UV-B–exposed side. The irradiated side shows (1) strong activation of flavonoid synthesis genes and flavonoid accumulation; (2) increased gibberellin (GA)2-oxidase expression, diminished GA1 levels, and accumulation of the DELLA protein REPRESSOR OF GA1; and (3) increased expression of the auxin transport regulator PINOID, contributing to diminished auxin signaling. Together, the data suggest a mechanism of phototropin-independent inflorescence phototropism through multiple, locally UVR8-regulated hormone pathways. Fil: Vanhaelewyn, Lucas. University of Ghent; Bélgica Fil: Viczián, András. Institute of Plant Biology, Biological Research Centre; Hungría Fil: Prinsen, Els. Universiteit Antwerp; Bélgica Fil: Bernula, Péter. Institute of Plant Biology, Biological Research Centre; Hungría. University of Szeged; Hungría Fil: Serrano, Alejandro Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentina Fil: Arana, Maria Veronica. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche. Instituto de Investigaciones Forestales y Agropecuarias Bariloche. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; Argentina Fil: Ballare, Carlos Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Biotecnológicas; Argentina Fil: Nagy, Ferenc. Institute of Plant Biology, Biological Research Centre; Hungría Fil: Van Der Straeten, Dominique. University of Ghent; Bélgica Fil: Vandenbussche, Filip. University of Ghent; Bélgica

The relief of dormancy and the promotion of seed germination are of extreme importance for a successful seedling establishment. Although alternating temperatures and light are signals promoting the relief of seed dormancy, the underlying mechanisms of their interaction in seeds are scarcely known. By exposing imbibed Arabidopsis thaliana dormant seeds to two-day temperature cycles previous of a red light pulse, we demonstrate that the germination mediated by phytochrome B requires the presence of functional PSEUDO-RESPONSE REGULATOR 7 (PRR7) and TIMING OF CAB EXPRESSION 1 (TOC1) alleles. In addition, daily cycles of alternating temperatures in darkness reduce the protein levels of DELAY OF GERMINATION 1 (DOG1), allowing the expression of TOC1 to induce seed germination. Our results suggest a functional role for some components of the circadian clock related with the action of DOG1 for the integration of alternating temperatures and light signals in the relief of seed dormancy. The synchronization of germination by the synergic action of light and temperature through the activity of circadian clock might have ecological and adaptive consequences. Fil: Arana, Maria Veronica. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Tognacca, Rocío Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina Fil: Estravis Barcala, Maximiliano. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Sanchez, Rodolfo Augusto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina Fil: Botto, Javier Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina

In several species, seed germination is regulated by light in a way that restricts seedling emergence to the environmental conditions that are likely to be favourable for the success of the new individual, and therefore, this behaviour is recognized to have adaptive value. The phytochromes are one of the most relevant photoreceptors involved in light perception by plants. We explored the redundancy and diversity functions of the phytochrome family in the control of seed responsiveness to light and gibberellins (GA) by using a set of phytochrome mutants of Arabidopsis. Our data show that, in addition to the well-known role of phyB in the promotion of germination in response to high red to far-red ratios (R/FR), phyE and phyD stimulate germination at very low R/FR ratios, probably by promoting the action of phyA. Further, we show that phyC regulates negatively the seed responsiveness to light, unravelling unexpected functions for phyC in seed germination. Finally, we find that seed responsiveness to GA is mainly controlled by phyB, with phyC, phyD and phyE having relevant roles when acting in a phyB-deficient background. Our results indicate that phytochromes have multiple and complex roles during germination depending on the active photoreceptor background.

The apical hook develops in the upper part of the hypocotyl when seeds buried in the soil germinate, and serves to protect cotyledons and the shoot apical meristem from possible damage caused by pushing through the soil. The curvature is formed through differential cell growth that occurs at the two opposite sides of the hypocotyl, and it is established by a gradient of auxin activity and refined by the coordinated action of auxin and ethylene. Here we show that gibberellins (GAs) promote hook development through the transcriptional regulation of several genes of the ethylene and auxin pathways in Arabidopsis. The level of GA activity determines the speed of hook formation and the extent of the curvature during the formation phase independently of ethylene, probably by modulating auxin transport and response through HLS1, PIN3, and PIN7. Moreover, GAs cooperate with ethylene in preventing hook opening, in part through the induction of ethylene production mediated by ACS5/ETO2 and ACS8.

[EN] Circadian clocks are endogenous timekeeping mechanisms that allow organisms to anticipate rhythmic, daily environmental changes. Temporal coordination of transcription results in a set of gene expression patterns with peak levels occurring at precise times of the day. An intriguing question is how a single clock can generate different oscillatory rhythms, and it has been proposed that hormone signaling might act in plants as a relay mechanism to modulate the amplitude and the phase of output rhythms. Here we show that the circadian clock gates gibberellin (GA) signaling through transcriptional regulation of the GA receptors, resulting in higher stability of DELLA proteins during daytime and higher GA sensitivity at night. Oscillation of GA signaling appears to be particularly critical for rhythmic growth, given that constitutive expression of the GA receptor expands the daily growth period in seedlings, and complete loss of DELLA function causes continuous, arrhythmic hypocotyl growth. Moreover, transcriptomic analysis of a pentuple della KO mutant indicates that the GA pathway mediates the rhythmic expression of many clock-regulated genes related to biotic and abiotic stress responses and cell wall modification. Thus, gating of GA sensitivity by the circadian clock represents an additional layer of regulation that might provide extra robustness to the diurnal growth rhythm and constitute a regulatory module that coordinates the circadian clock with additional endogenous and environmental signals., We are indebted to the Nottingham Arabidopsis Stock Centre, Stephen G. Thomas, Tai-ping Sun, and Nicholas P. Harberd for providing us with seeds. M. V. A. was the recipient of a postdoctoral contract from the Spanish Ministry of Science and Innovation for the mobility of young researchers into Spanish universities. N.A.M. holds a Consejo Superior de Investigaciones Cientificas Fellowship of the JAE-Pre program. This study was supported by Spanish Ministry of Science and Innovation Grants BIO2007-60923, BIO2010-15071, and CSD2007-00057; Generalitat Valenciana Grants ACOMP/2010/190; and National Science Foundation Grants DBI0820854 and IOS0923752.

Seed germination can be promoted by the modes of action of two of the phytochromes: the low-fluence response (LFR), which is the classical red (R)-far-red (FR) reversible response and the very-low-fluence response (VLFR) that can be saturated by extremely low levels of Pfr, which can be elicited by a saturating FR pulse. The Datura ferox seed population used in this work had acquired the capacity to germinate through a VLFR after pretreatment in a water-saturated atmosphere (WSA) at constant 25 degrees C. After 12 d in WSA germination after a FR pulse was 82%, while it was less than 10% in darkness. It was found that the VLFR of germination is associated with increments in the embryo growth potential (EGP) and in the activity of two enzymes related to the weakening of the micropylar region of the endosperm (ME); endo-beta-mannanase and beta-mannosidase. The FR pulse also significantly stimulated the expression of DfGA3ox, a GA 3beta-hydroxylase, suggesting that the promotion of germination by the VLFR is associated with an increase in the synthesis of active gibberellins. The promotive action of the VLFR on germination is reduced when the FR pulse is immediately followed by a continuous FR treatment for 24 h (FRc). The effect of FRc cannot be reproduced by hourly FR pulses during the same period, showing that the antagonistic effect of FRc is a high-irradiance response (HIR). The action of the HIR in germination is associated with a decrease of both the mannan-degrading enzyme activity and the expression of DfMan in the ME, whereas no changes in the EGP were observed. The HIR also inhibits the accumulation of DfGA3ox in embryos, indicating that its action on germination is mediated, at least in part, through the modulation of active GA contents in seeds. This is the first report of a gene that participates in the VLFR-HIR antagonism in seeds.

Seeds integrate environmental cues that modulate their dormancy and germination. Although many mechanisms have been identified in laboratory experiments, their contribution to germination dynamics in existing communities and their involvement in defining species habitats remain elusive. By coupling mathematical models with ecological data we investigated the contribution of seed temperature responses to the dynamics of germination of three Nothofagus species that are sharply distributed across different altitudes in the Patagonian Andes. Seed responsiveness to temperature of the three Nothofagus species was linked to the thermal characteristics of their preferred ecological niche. In their natural distribution range, there was overlap in the timing of germination of the species, which was restricted to mid-spring. By contrast, outside their species distribution range, germination was temporally uncoupled with altitude. This phenomenon was described mathematically by the interplay between interspecific differences in seed population thermal parameters and the range in soil thermic environments across different altitudes. The observed interspecific variations in seed responsiveness to temperature and its environmental regulation, constitute a major determinant of the dynamics of Nothofagus germination across elevations. This phenomenon likely contributes to the maintenance of patterns of species abundance across altitude by placing germinated seeds in a favorable environment for plant growth. Fil: Arana, María Verónica. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Gonzalez Polo, Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación En Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina Fil: Martinez Meier, Alejandro. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche; Argentina Fil: Gallo, Leonardo Ariel. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche; Argentina Fil: Benech-arnold, Roberto Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina Fil: Sanchez, Rodolfo Augusto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas A la Agricultura; Argentina Fil: Batlla, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina

Since the discovery of melatonin in plants, several roles have been described for different species, organs, and developmental stages. Arabidopsis thaliana, being a model plant species, is adequate to contribute to the elucidation of the role of melatonin in plants. In this work, melatonin was monitored daily by UHPLC-MS/MS in leaves, in order to study its diurnal accumulation as well as the effects of natural and artificial light treatments on its concentration. Furthermore, the effects of exogenous application of melatonin to assess its role in seed viability after heat stress and as a regulator of growth and development of vegetative tissues were evaluated. Our results indicate that melatonin contents in Arabidopsis were higher in plants growing under natural radiation when compared to those growing under artificial conditions, and its levels were not diurnally-regulated. Exogenous melatonin applications prolonged seed viability after heat stress conditions. In addition, melatonin applications retarded leaf senescence. Its effects as growth promoter were dose and tissue-dependent; stimulating root growth at low concentrations and decreasing leaf area at high doses. Fil: Gatica Hernández, Ismaél Jairo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Instituto de Biología Agrícola de Mendoza; Argentina Fil: Gomez, Federico Jose Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Instituto de Biología Agrícola de Mendoza; Argentina Fil: Cerutti, Estela Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Química de San Luis. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Instituto de Química de San Luis; Argentina Fil: Arana, Maria Veronica. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Silva, María Fernanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Instituto de Biología Agrícola de Mendoza; Argentina

Phytochromes mediate a profound developmental shift when dark-grown seedlings are exposed to light. Here, we show that a subset of genes is upregulated in phytochrome B (phyB) mutants even before dark-grown Arabidopsis thaliana seedlings are exposed to light. Most of these genes bear the RY cis motif, which is a binding site of the transcription factor ABSCISIC ACID INSENSITIVE3 (ABI3), and the phyB mutation also enhances ABI3 expression. These changes in transcriptome have physiological consequences, because seedlings of the abi3 mutant showed enhanced responses to pulses of far-red light, whereas ABI3 overexpressers exhibited the opposite pattern. Seedlings of the wild type derived from seeds germinated in full darkness showed enhanced expression of genes bearing the RY cis motif and reduced responses to farred light. We propose that, via changes in ABI3 expression, light, perceived mainly by phyB in the seed, generates a downstream transdevelopmental phase signal that preconditions the seedling to its most likely environment. Fil: Mazzella, Maria Agustina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; Argentina Fil: Arana, Maria Veronica. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina Fil: Staneloni, Roberto Julio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Fundación Instituto Leloir; Argentina Fil: Perelman, Susana Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina Fil: Rodríguez Batiller, María Jose. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Fundación Instituto Leloir; Argentina Fil: Muschietti, Jorge Prometeo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; Argentina Fil: Cerdan, Pablo Diego. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Salk Institute for Biological Studies; Estados Unidos Fil: Chen, Kunhua. Salk Institute for Biological Studies; Estados Unidos Fil: Sanchez, Rodolfo Augusto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina Fil: Zhu, Tong. Syngenta Biotechnology; Estados Unidos Fil: Chory, Joanne. Salk Institute for Biological Studies; Estados Unidos Fil: Casal, Jorge José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina

The circadian clock acts as central coordinator of plant activity, and it regulates key traits for plant fitness such as flowering time, gas exchange, growth, and stress responses. In the May issue of the Proceedings of the National Academy of Science we describe the circadian regulation of gibberellin (GA) signaling, through transcriptional control of GA receptor genes (GID1a and GID1b). We show that, in short day photocycles, the expression of GA receptors oscillates in seedlings, yielding a window of strong GA activity at the end of the night that overlaps with the period of maximum growth. This clock-mediated control of GA signaling is not only crucial for the establishment of rhythmic patterns of growth but also affects the expression of many circadian-controlled genes that participate in a wide range of biological processes. Here we propose a possible mechanism that might operate for the transcriptional control of GID1 expression by the circadian clock.

An enriched genomic library was constructed and 9 novel polymorphic tetranucleotide microsatellite markers developed for Austrocedrus chilensis, the most economically important native conifer in the Andean Patagonian region. Polymorphism was investigated for these markers in 48 individuals from two populations. Numbers of alleles ranged from 3 to 19 and levels of observed heterozygosity among the 9 loci ranged from 0.32 to 0.95. No locus combinations exhibited linkage disequilibrium. These polymorphic markers will be useful tools for the study of demography and gene flow and more in general for population and conservation genetics of this species.

The circadian clock acts as central coordinator of plant activity, and it regulates key traits for plant fitness such as flowering time, gas exchange, growth, and stress responses. In the May issue of the Proceedings of the National Academy of Science we describe the circadian regulation of gibberellin (GA) signaling, through transcriptional control of GA receptor genes (GID1a and GID1b). We show that, in short day photocycles, the expression of GA receptors oscillates in seedlings, yielding a window of strong GA activity at the end of the night that overlaps with the period of maximum growth. This clock-mediated control of GA signaling is not only crucial for the establishment of rhythmic patterns of growth but also affects the expression of many circadian-controlled genes that participate in a wide range of biological processes. Here we propose a possible mechanism that might operate for the transcriptional control of GID1 expression by the circadian clock.

An enriched genomic library was constructed and 9 novel polymorphic tetranucleotide microsatellite markers developed for Austrocedrus chilensis, the most economically important native conifer in the Andean Patagonian region. Polymorphism was investigated for these markers in 48 individuals from two populations. Numbers of alleles ranged from 3 to 19 and levels of observed heterozygosity among the 9 loci ranged from 0.32 to 0.95. No locus combinations exhibited linkage disequilibrium. These polymorphic markers will be useful tools for the study of demography and gene flow and more in general for population and conservation genetics of this species.

Knowledge about current patterns of genetic structure of populations together with the evolutionary history of a species helps to understand and predict the adaptation of populations to future climate change. We assayed variation at nuclear microsatellite markers among peripheral vs. continuous populations of the temperate South American species Austrocedrus chilensis, to investigate the role of historical vs. demographical forces in shaping population genetic structure. This species occurs in continuous populations in the west and central distribution range, but becomes highly fragmented at the eastern limit, which comprised ice-free areas during Quaternary glaciations and has extreme climatic conditions at present times. Bayesian analysis methods identified two contrasting patterns of genetic structure; (I) populations from humid, mesic and peri-glacial regions formed a single deme with relatively low genetic differentiation and high admixture levels whereas (II) a highly heterogeneous genetic structure with low level of admixture was found in the steppe, towards the east and northeast limit of the distribution range. In the steppe, population fragmentation, restricted gene flow and isolation-by-distance were also inferred. In addition, several small steppe populations showed high genetic diversity and divergent gene pools, suggesting that they constitute ancient refuges from pre-Holocene glaciations with just a subgroup of them contributing significantly to post-glacial spread. These results are discussed in relation to patterns of genetic variation found for other temperate species and the contribution of the particular southern Andes topography and climate to post-glacial spread.

The promotion of germination by phytochrome is associated with extensive changes both in the embryo and in the micropylar region of the endosperm (ME) of Datura ferox seeds. These changes require de novo gibberellins (GAs) biosynthesis in the embryo, the site where the light stimulus is perceived. GAs stimulate embryo growth potential and move to ME, promoting the expression of genes related with weakening. We report here that, in addition, phytochrome stimulates the sensitivity of the seeds to gibberellic acid (GA). The phytochrome-induced signal is produced in the embryo and enhances the stimulus by GA of embryo growth potential (EGP) and the promotion of the expression of proteins thought to participate in ME weakening: endo-beta-mannanase (EC 3.2.1.78), endo-beta-mannosidase (EC 3.2.1.25) and expansin. Our results suggest that the cytokinins may be a component of the embryonic signal. Phytochrome also modulates DfPHOR and DfMYB transcript levels in ME. These genes show a high identity with components of GAs signaling identified in other species. Expression of DfPHOR in the ME is apparently regulated by phytochrome through the supply of GAs from the embryo to ME, whereas DfMYB expression is regulated by an embryonic factor with some of the characteristics of the one that modulates seed sensitivity to GAs.