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Arias, M. B., Poupin, M. J., & Lardies, M. A. (2011). Plasticity of life-cycle, physiological thermal traits and Hsp70 gene expression in an insect along the ontogeny: Effect of temperature variability. J. Therm. Biol., 36(6), 355–362.
Abstract: It is considered that extreme environmental temperature, rather than mean temperatures exert a selective pressure in ectotherms. Consequently, it is important to understand how the predicted increase in temperature variance with a higher frequency of extreme events in climate change is likely to impact on organisms. Thermal tolerance traits (i.e. chill-coma, recovery time, Hsp70 expression) are directly linked with performance in ectotherms and have consequences in life-history traits. We examined the effects of temperature variability on thermal tolerance and life-history traits through ontogeny of an insect with a complex life-cycle: the yellow mealworm beetle Tenebrio molitor. We established two common gardens with 100 recently ovoposited eggs each. Larvae were reared from hatching to adult on either a variable (mean=18 degrees C and a variance of 6.8 degrees C) or constant (18 +/- 1 degrees C) thermal environment. Development rate and growth rate were similar between thermal environments. Results indicate that larvae reared in a variable environment are more cold-tolerant than larvae of a constant environment. Interestingly, these results are reversed in the adult stage, outlining an inter-stage physiological cost. Gene expression pattern of an Hsp70 gene was well correlated with larval thermotolerance to cold in the variable environment but higher gene expression in adults is not correlated with individual's thermotolerance. We conclude that chill-coma, recovery time and Hsp70 gene expression are plastic in response to a thermal environment but also change significantly their responses depending on the ontogenetic stage, implying that the response of adult individuals is linked to early stages of the life-cycle. (C) 2011 Elsevier Ltd. All rights reserved,
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Barrientos-Diaz, L., Gidekel, M., & Gutierrez-Moraga, A. (2008). Characterization of rhizospheric bacteria isolated from Deschampsia antarctica Desv. World J. Microbiol. Biotechnol., 24(10), 2289–2296.
Abstract: Deschampsia antarctica Desv. is the only gramineae capable of colonizing the Antarctic due to the region's extreme climate and soil environment. In the present research, bacteria colonizing the rhizospheric soil of D. antarctica were isolated and characterized. The soil studies showed that D. antarctica possesses a wide spectrum of psychrotolerant bacteria with extensive and varied antibiotic resistance, as well as heavy metal tolerance. The bacterial strains isolated from the rhizosphere of D. antarctica also produced a diverse pattern of enzymes. Based on the strain identification with partial characterization of the 16S rRNA gene, the majority of the isolates correspond to different Pseudomonas species, and species of the genus Flavobacterium sp. and Arthrobacter sp. The isolated strains collected from this research constitute a unique collection for future, more detailed taxonomic analysis and physiological characterization, contributing to the search for potential biotechnological uses. These findings and others have great potential for developing new biotechnological products from Antarctic microorganisms.
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Fraigniaud, P., Montealegre, P., Rapaport, I., & Todinca, I. (2023). Alert Results A Meta-Theorem for Distributed Certification 5 of 28 A Meta-Theorem for Distributed Certification. Algorithmica, Early Access.
Abstract: Distributed certification, whether it be proof-labeling schemes, locally checkable proofs, etc., deals with the issue of certifying the legality of a distributed system with respect to a given boolean predicate. A certificate is assigned to each process in the system by a non-trustable oracle, and the processes are in charge of verifying these certificates, so that two properties are satisfied: completeness, i.e., for every legal instance, there is a certificate assignment leading all processes to accept, and soundness, i.e., for every illegal instance, and for every certificate assignment, at least one process rejects. The verification of the certificates must be fast, and the certificates themselves must be small. A large quantity of results have been produced in this framework, each aiming at designing a distributed certification mechanism for specific boolean predicates. This paper presents a “meta-theorem”, applying to many boolean predicates at once. Specifically, we prove that, for every boolean predicate on graphs definable in the monadic second-order (MSO) logic of graphs, there exists a distributed certification mechanism using certificates on O(log(2) n) bits in n-node graphs of bounded treewidth, with a verification protocol involving a single round of communication between neighbors
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Gaitan-Espitia, J. D., Bacigalupe, L. D., Opitz, T., Lagos, N. A., Timmermann, T., & Lardies, M. A. (2014). Geographic variation in thermal physiological performance of the intertidal crab Petrolisthes violaceus along a latitudinal gradient. J. Exp. Biol., 217(24), 4379–4386.
Abstract: Environmental temperature has profound effects on the biological performance and biogeographical distribution of ectothermic species. Variation of this abiotic factor across geographic gradients is expected to produce physiological differentiation and local adaptation of natural populations depending on their thermal tolerances and physiological sensitivities. Here, we studied geographic variation in whole-organism thermal physiology of seven populations of the porcelain crab Petrolisthes violaceus across a latitudinal gradient of 3000 km, characterized by a cline of thermal conditions. Our study found that populations of P. violaceus show no differences in the limits of their thermal performance curves and demonstrate a negative correlation of their optimal temperatures with latitude. Additionally, our findings show that high-latitude populations of P. violaceus exhibit broader thermal tolerances, which is consistent with the climatic variability hypothesis. Interestingly, under a future scenario of warming oceans, the thermal safety margins of P. violaceus indicate that lower latitude populations can physiologically tolerate the ocean-warming scenarios projected by the IPCC for the end of the twenty-first century.
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Lardies, M. A., Arias, M. B., Poupin, M. J., & Bacigalupe, L. D. (2014). Heritability of hsp70 expression in the beetle Tenebrio molitor: Ontogenetic and environmental effects. J. Insect Physiol., 67, 70–75.
Abstract: Ectotherms constitute the vast majority of terrestrial biodiversity and are especially likely to be vulnerable to climate warming because their basic physiological functions such as locomotion, growth, and reproduction are strongly influenced by environmental temperature. An integrated view about the effects of global warming will be reached not just establishing how the increase in mean temperature impacts the natural populations but also establishing the effects of the increase in temperature variance. One of the molecular responses that are activated in a cell under a temperature stress is the heat shock protein response (HSP). Some studies that have detected consistent differences among thermal treatments and ontogenetic stages in HSP70 expression have assumed that these differences had a genetic basis and consequently expression would be heritable. We tested for changes in quantitative genetic parameters of HSP70 expression in a half-sib design where individuals of the beetle Tenebrio molitor were maintained in constant and varying thermal environments. We estimated heritability of HSP70 expression using a linear mixed modelling approach in different ontogenetic stages. Expression levels of HSP70 were consistently higher in the variable environment and heritability estimates were low to moderate. The results imply that within each ontogenetic stage additive genetic variance was higher in the variable environment and in adults compared with constant environment and larvae stage, respectively. We found that almost all the genetic correlations across ontogenetic stages and environment were positive. These suggest that directional selection for higher levels of expression in one environment will result in higher expression levels of HSP70 on the other environment for the same ontogenetic stage. (C) 2014 Elsevier Ltd. All rights reserved.
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Ledger, T., Rojas, S., Timmermann, T., Pinedo, I., Poupin, M. J., Garrido, T., et al. (2016). Volatile-Mediated Effects Predominate in Paraburkholderia phytofirmans Growth Promotion and Salt Stress Tolerance of Arabidopsis thaliana. Front. Microbiol., 7, 18 pp.
Abstract: Abiotic stress has a growing impact on plant growth and agricultural activity worldwide. Specific plant growth promoting rhizobacteria have been reported to stimulate growth and tolerance to abiotic stress in plants, and molecular mechanisms like phytohormone synthesis and 1-aminocyclopropane-1-carboxylate deamination are usual candidates proposed to mediate these bacterial effects. Paraburkholderia phytofirmans PsJN is able to promote growth of several plant hosts, and improve their tolerance to chilling, drought and salinity. This work investigated bacterial determinants involved in PsJN stimulation of growth and salinity tolerance in Arabidopsis thaliana, showing bacteria enable plants to survive long-term salinity treatment, accumulating less sodium within leaf tissues relative to non-inoculated controls. Inactivation of specific bacterial genes encoding ACC deaminase, auxin catabolism, N-acyl-homosenne-lactone production, and flagellin synthesis showed these functions have little influence on bacterial induction of salinity tolerance. Volatile organic compound emission from strain PsJN was shown to reproduce the effects of direct bacterial inoculation of roots, increasing plant growth rate and tolerance to salinity evaluated both in vitro and in soil. Furthermore, early exposure to VOCs from P phytofirmans was sufficient to stimulate long-term effects observed in Arabidopsis growth in the presence and absence of salinity. Organic compounds were analyzed in the headspace of PsJN cultures, showing production of 2-undecanone, 7-hexanol, 3-methylbutanol and dimethyl disulfide. Exposure of A. thaliana to different quantities of these molecules showed that they are able to influence growth in a wide range of added amounts. Exposure to a blend of the first three compounds was found to mimic the effects of PsJN on both general growth promotion and salinity tolerance. To our knowledge, this is the first report on volatile compound-mediated induction of plant abiotic stress tolerance by a Paraburkholderia species.
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Pinedo, I., Ledger, T., Greve, M., & Poupin, M. J. (2015). Burkholderia phytofirmans PsJN induces long-term metabolic and transcriptional changes involved in Arabidopsis thaliana salt tolerance. Front. Plant Sci., 6, 17 pp.
Abstract: Salinity is one of the major limitations for food production worldwide. Improvement of plant salt-stress tolerance using plant-growth promoting rhizobacteria (PGPR) has arisen as a promising strategy to help overcome this limitation. However, the molecular and biochemical mechanisms controlling PGPR/plant interactions under salt-stress remain unclear. The main objective of this study was to obtain new insights into the mechanisms underlying salt-stress tolerance enhancement in the salt-sensitive Arabidopsis thaliana Col-0 plants, when inoculated with the well-known PGPR strain Burkholderia phytofirmans PsJN. To tackle this, different life history traits, together with the spatiotemporal accumulation patterns for key metabolites and salt-stress related transcripts, were analyzed in inoculated plants under short and long-term salt-stress. Inoculated plants displayed faster recovery and increased tolerance after sustained salt-stress. PsJN treatment accelerated the accumulation of proline and transcription of genes related to abscisic acid signaling (Relative to Dessication, RD29A and RD29B), ROS scavenging Oscorbate Peroxidase 2), and detoxification (Glyoxalase I 7), and down-regulated the expression of Lipoxygenase 2 (related to jasmonic acid biosynthesis). Among the general transcriptional effects of this bacterium, the expression pattern of important ion-homeostasis related genes was altered after short and longterm stress (Arabidopsis K Transporter 1, High-Affinity K Transporter 1, Sodium Hydrogen Exchanger 2, and Arabidopsis Salt Overly Sensitive 1). In all, the faster and stronger molecular changes induced by the inoculation suggest a PsJN-priming effect, which may explain the observed tolerance after short-term and sustained salt-stress in plants. This study provides novel information about possible mechanisms involved in salt-stress tolerance induced by PGPR in plants, showing that certain changes are maintained over time. This opens up new venues to study these relevant biological associations, as well as new approaches to a better understanding of the spatiotemporal mechanisms involved in stress tolerance in plants.
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Ramajo, L., Fernandez, C., Nunez, Y., Caballero, P., Lardies, M. A., & Poupin, M. J. (2019). Physiological responses of juvenile Chilean scallops (Argopecten purpuratus) to isolated and combined environmental drivers of coastal upwelling. ICES J. Mar. Sci., 76(6), 1836–1849.
Abstract: Coastal biota is exposed to continuous environmental variability as a consequence of natural and anthropogenic processes. Responding to heterogeneous conditions requires the presence of physiological strategies to cope with the environment. Ecosystems influenced by upwelling endure naturally cold, acidic and hypoxic conditions, nevertheless they sustain major fisheries worldwide. This suggests that species inhabiting upwelling habitats possess physiological adaptations to handle high environmental variability. Here, we assessed the impact of the main upwelling drivers (temperature, pH and oxygen) in isolation and combined on eco-physiological responses of Chilean scallop Argopecten purpuratus. A. purpuratus responded to hypoxia by increasing their metabolic performance to maintain growth and calcification. Calcification was only affected by pH and increased under acidic conditions. Further, A. purpuratus juveniles prioritized calcification at the expense of growth under upwelling conditions. Increasing temperature had a significant impact by enhancing the physiological performance of A. purpuratus juveniles independently of oxygen and pH conditions, but this was associated with earlier and higher mortalities. Our results suggest that A. purpuratus is acclimated to short-term colder, acidic and hypoxic conditions, and provide important information of how this species responds to the heterogeneous environment of upwelling, which is significantly relevant in the climatic context of upwelling intensification.
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Ramajo, L., Marba, N., Prado, L., Peron, S., Lardies, M. A., Rodriguez-Navarro, A. B., et al. (2016). Biomineralization changes with food supply confer juvenile scallops (Argopecten purpuratus) resistance to ocean acidification. Glob. Change Biol., 22(6), 2025–2037.
Abstract: Future ocean acidification (OA) will affect physiological traits of marine species, with calcifying species being particularly vulnerable. As OA entails high energy demands, particularly during the rapid juvenile growth phase, food supply may play a key role in the response of marine organisms to OA. We experimentally evaluated the role of food supply in modulating physiological responses and biomineralization processes in juveniles of the Chilean scallop, Argopecten purpuratus, that were exposed to control (pH similar to 8.0) and low pH (pH similar to 7.6) conditions using three food supply treatments (high, intermediate, and low). We found that pH and food levels had additive effects on the physiological response of the juvenile scallops. Metabolic rates, shell growth, net calcification, and ingestion rates increased significantly at low pH conditions, independent of food. These physiological responses increased significantly in organisms exposed to intermediate and high levels of food supply. Hence, food supply seems to play a major role modulating organismal response by providing the energetic means to bolster the physiological response of OA stress. On the contrary, the relative expression of chitin synthase, a functional molecule for biomineralization, increased significantly in scallops exposed to low food supply and low pH, which resulted in a thicker periostracum enriched with chitin polysaccharides. Under reduced food and low pH conditions, the adaptive organismal response was to trade-off growth for the expression of biomineralization molecules and altering of the organic composition of shell periostracum, suggesting that the future performance of these calcifiers will depend on the trajectories of both OA and food supply. Thus, incorporating a suite of traits and multiple stressors in future studies of the adaptive organismal response may provide key insights on OA impacts on marine calcifiers.
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Romero-Romero, J. L., Inostroza-Blancheteau, C., Orellana, D., Aquea, F., Reyes-Diaz, M., Gil, P. M., et al. (2018). Stomata regulation by tissue-specific expression of the Citrus sinensis MYB61 transcription factor improves water-use efficiency in Arabidopsis. Plant Physiol. Biochem., 130, 54–60.
Abstract: Water-use efficiency (WUE) is a quantitative measurement of biomass produced per volume of water transpired by a plant. WUE is an important physiological trait for drought response to mitigate the water deficiency. In this work, a cisgenic construction from Citrus sinensis was developed and its function in the improvement of WUE was evaluated in Arabidopsis. Sequences of the CsMYB61 coding region, a transcription factor implicated in the closure of stomata, together with a putative stomata-specific promoter from CsMYB.1.5, were identified and cloned. The protein encoded in the CsMYB61 locus harbors domains and motifs characteristic of MYB61 proteins. In addition, a 1.2 kb promoter region of the gene CsMYB15 (pCsMYB15) containing regulatory elements for expression in guard cells and in response to Abscisic Acid (ABA) and light was isolated. In Arabidopsis, pCsMYB15 directs the expression of the reporter gene GUS in stomata in the presence of light. In addition, transgenic lines expressing the CsMYB61 coding region under transcriptional control of pCsMYB15 have a normal phenotype under in vitro and greenhouse conditions. These transgenic lines exhibited a smaller opening of the stomata pore, lower stomatal conductance and respiration rate, enhanced sensitivity to exogenous ABA, and high drought stress tolerance. Our results indicate that stomata-specific expression of CsMYB61 enhances water use efficiency under drought conditions in Arabidospis.
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Romero-Romero, J. L., Inostroza-Blancheteau, C., Reyes-D?az, M., Matte, J. P., Aquea, F., Espinoza, C., et al. (2020). Increased Drought and Salinity Tolerance in Citrus aurantifolia (Mexican Lemon) Plants Overexpressing Arabidopsis CBF3 Gene. J. Soil Sci. Plant Nutr., 20(1), 244–252.
Abstract: Citrus are a globally important fruit crop. Abiotic stressors such as drought and salinity adversely affect physiological citrus performance and survival. With the aim of improving drought tolerance in citrus plants, we constructed transgenic lines of Citrus lemon overexpressing the Arabidopsis transcription factor CBF3. Molecular, physiological, and quantitative real-time analyses showed high expression of AtCBF3 in three selected transgenic lines. During a 15-day treatment of water deficit by cessation of irrigation, the transgenic lines LM2 and LM14 showed lower stomatal conductance and transpiration paired with lower photosynthesis, whereas transgenic line LM7 maintained its photosynthesis, declining stomatal conductance, and transpiration compared to WT plants, which is manifested into more efficient water use. The genes CsRafS1 and CsGolS1 showed similar or greater expression in one of the transgenic lines with respect to control plants. Moreover, transgenic lines were more tolerant to saline stress and presented a greener phenotype with increased chlorophyll content in leaf discs compared to WT plants. In addition, a lower electrical conductivity in solution was observed in transgenic lines. Furthermore, all transgenic lines exhibited significantly less accumulation of reactive oxygen species than WT plants. Together, these results suggest the potential for heterologous expression of the AtCBF3 gene to mediate tolerance to hydric and saline stress in citrus plants.
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Viveros, M. F. A., Inostroza-Blancheteau, C., Timmermann, T., Gonzalez, M., & Arce-Johnson, P. (2013). Overexpression of GlyI and GlyII genes in transgenic tomato (Solanum lycopersicum Mill.) plants confers salt tolerance by decreasing oxidative stress. Mol. Biol. Rep., 40(4), 3281–3290.
Abstract: The glyoxalase system plays an important role in various physiological processes in plants, including salt stress tolerance. We report the effects of overexpressing glyoxalase I and glyoxalase II genes in transgenic tomato (Solanum lycopersicum Mill.) cv. Ailsa Craig. Stable expression of both transgenes was detected in the transformed tomato plants under salt stress. The transgenic lines overexpressing GlyI and GlyII under a high NaCl concentration (800 mM) showed reduced lipid peroxidation and the production of H2O2 in leaf tissues. A greater decrease in the chlorophyll a+b content in wild-type (WT) compared with transgenic lines was also observed. These results suggest that the over expression of two genes, GlyI and GlyII, may enhance salt stress tolerance by decreasing oxidative stress in transformed tomato plants. This work will help our understanding of the putative role of the glyoxalase system in the tolerance to abiotic stress in tomato plants.
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