We assessed influence of three acclimation regimes and influence of recovery after cold shock (exposure to 0°C for a period of time corresponding to Lt25) on the relative mRNA levels of selected stress proteins using qRT-PCR method. Larvae acclimated at 25°C showed relatively weak upregulation responses to cold shock. Much stronger responses were observed in the larvae that were cold-acclimated at 15°C or 15°C ? 6°C prior to cold shock. Two different general trends were distinguished in the response to cold acclimation and cold shock: (a) proteins from families SP70 and SP90 and splice variants c and d of the transcription factor HSF were upregulated in response to cold acclimation and the levels of their mRNA transcripts further increased after cold shock (for instance, the abundance of hsp70Aa mRNA increased up to 300-fold after cold shock (acclimation variant 15°C ? 6°C)); (b) four members of the small Hsp family (22, 23, 26 and 27 kDa) and splice variants a and b of the transcription factor HSF were down-regulated during cold acclimation (for instance, 10-fold in the case of hsp22) and the levels of their mRNA transcripts were either unchanged or increased only moderately after the cold shock. A third group of proteins, namely Hsc70, Hsp40 showed no or relatively small changes.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / The occurrence of short droughts, during the growing season of cassava in Rio Grande do Sul, may cause several soil drying cycles which induce physiological disorders in plants, affecting cassava productivity in the state. The objectives of this study were to verify the physiological mechanisms used by plants during the first and second soil drying cycle, the recovery of leaf area in plants under water stress after rehydration, the response of plants under one drying cycle with two distinct physiological ages and the possibility of acclimation of plants under two drying cycles, in sequence. Two experiments were conducted with cassava plants, Fepagro RS 13 cultivar, inside a plastic house at Federal University of Santa Maria, RS, Brazil. Planting dates were on 29/09/2011 for EXP 1 and 24/11/2011 for EXP 2. Water regimes for the two experiments were RH1, without water deficit during the two periods (control treatment); RH2, with water deficit during the two periods (two cycling cycles); RH3, with one drying cycle on P1, matching with the first drying cycle on RH2 and RH4, with one drying cicle on P2, matching with the second drying cycle on RH2. FTSW is the portion of available water in the soil which plants use in the transpiration. The physiological mechanisms that stood out on P1 of RH2 and RH3 and P2 of RH4 were the reduction of total leaf area and stomatal control of cassava plants. On P2 of RH2, it was the reduction of total leaf area (without leaf senescence). RH3 plants showed fast recovering after rehydration on P2, with high NFE and CFA, regarding RH1. The drying cycles with low (RH3) and high (RH4) physiological age presented no difference on FTSW threshold for TR and CFR. The high CT of RH2, on P2 of EXP1, indicates that plants had lower activation of stomatal control during high DPV periods. Thus, plants of RH2 acclimated to the second drying cycle with FTSW threshold of 0,09 to CFR and 0,13 to TR, presenting late CFR and TR declines in comparison with drying cycles of RH3 and RH4. / A frequente ocorrência de curtas estiagens, durante o período de cultivo da mandioca no Rio Grande do Sul, pode provocar vários ciclos de secamento do solo que causam distúrbios fisiológicos nas plantas, afetando a produtividade da cultura no Estado. Os objetivos desta dissertação foram verificar os mecanismos fisiológicos das plantas durante o primeiro e segundo ciclo de secamento do solo; a capacidade de recuperação da área foliar em plantas com estresse hídrico após a reidratação; a resposta de plantas submetidas a um ciclo de secamento do solo em duas idades fisiológicas distintas e a possibilidade de aclimatação das plantas submetidas a dois ciclos de secamento do solo subsequentes. Dois experimentos foram conduzidos com plantas de mandioca, cultivar Fepagro RS 13, dentro de um abrigo telado no Departamento de Fitotecnia da Universidade Federal de Santa Maria, RS, Brasil. As datas de plantio do primeiro (EXP 1) e segundo (EXP 2) experimento foi 29/09/2011 e 24/11/2011, respectivamente. Os regimes hídricos do solo, para os dois experimentos, foram: RH1, sem deficiência hídrica nos dois períodos (testemunha); RH2, com deficiência hídrica nos dois períodos (dois ciclos de secamento do solo); RH3, com um ciclo de secamento no P1, coincidindo com o primeiro ciclo de secamento do RH2; e RH4, com um ciclo de secamento no P2, coincidindo com o segundo ciclo de secamento do RH2. A fração da água disponível do solo (FATS) é a parcela da água que a planta utiliza na transpiração. Os mecanismos fisiológicos mais evidenciados no P1 dos RH2 e RH3 e no P2 do RH4 foram a redução da área foliar total e o controle estomático das plantas de mandioca. Já, no P2 do RH2, foi a redução da área foliar total (sem senescência foliar). As plantas do RH3 demonstraram rápida recuperação após a reidratação no P2, com elevados NFE e CFA, em relação ao RH1. Os ciclos de secamento das plantas com menor (RH3) e maior (RH4) idade fisiológica não apresentaram diferença nas FATSc para TR e CFR. O elevado CT do RH2, no P2 do EXP 1, indica que as plantas tiveram menor ativação do controle estomático durante os períodos do dia de alto DPV. Com isso, as plantas do RH2 aclimataram-se ao segundo ciclo de secamento do solo com FATSc de 0,09 para CFR e de 0,13 para TR, apresentando os declínios de CFR e de TR mais tardiamente em comparação com os ciclos de secamento do RH3 e RH4.

Scleractinian corals are the ‘engineers’ of tropical coral reef ecosystems. Their three-dimensional structure provides habitat for thousands of fish and invertebrate species. The persistence of corals is threatened by climate change. In this study I investigated if corals may be able to increase tolerance to ocean warming through developmental acclimation, i.e. if corals that experience warmer temperatures during embryonic and larval development are better able to cope with higher temperatures later in life. Larvae of the broadcast spawning coral Montastraea cavernosa were raised at ambient (29°C) and future projected ocean warming temperatures (+2°C, 31°C). After larval settlement, coral juveniles from each treatment were split and reared for two months at either current or +2°C conditions. Larvae reared at the warmer temperature had lower survival and displayed a smaller size at settlement. Juveniles that were in the warmer conditions had faster growth rates. Individuals raised during larval and juvenile stages at 31°C had faster growth rates than individuals only in the elevated temperature treatment after settlement, thus indicating that developmental acclimation may have occurred. However, the highest mortality also occurred in this treatment, therefore the growth results could also be explained by positive selection of the most thermally tolerant individuals. My results suggest that acclimation and/or directed selection may help corals withstand future rises in ocean temperature.

Abstract Natural seasonal variation and the effects of cold treatment and nitrogen fertilization on protein expression with special emphasis on dehydrin proteins, were studied using different aged Scots pine (Pinus sylvestris L.). Several different dehydrins were found and their expression depended on the tissue type, tree age or specific treatment. Their concentrations fluctuated seasonally and in response to nitrogen fertilization, but no effects of low temperature on the dehydrins of seedlings were observed. A 60-kDa dehydrin was associated with cold acclimation in the bud and bark tissues of mature trees and in the needles of seedlings. In the needles of mature trees, this dehydrin was associated with springtime desiccation, which was detected as a significant decrease in the osmotic potential of needles. The quantity and quality of soluble proteins altered seasonally in Scots pine tissues, but low temperature treatment alone did not have any effect on the proteins. Soluble protein concentration increased during autumn and decreased in spring in buds and bark, but not in the needles of mature trees. In needles of seedlings, however, protein concentrations altered seasonally. Several proteins, of varying molecular weights, were more abundant in winter in all the tissues studied and some increased in concentration in the nitrogen-fertilized seedlings. The role of these proteins as a storage reserve in Scots pine is discussed. The osmotic potential of needles showed seasonal fluctuation, being high in the summer and low during the winter. Low temperature treatment decreased the osmotic and water potential of needles and increased the concentrations of soluble sugars in seedlings. Based on carbohydrate analyses, the metabolism of seedlings acclimated to low temperature in less than ten days. Nitrogen fertilization increased the content of total nitrogen and the soluble protein concentrations in the needles of seedlings and the growth both in the mature trees and seedlings. Although the frost resistance showed no response to nitrogen-fertilization, the soluble proteins and dehydrins were affected in a manner that suggested an earlier growth resumption of spring in the fertilized trees.

A primary goal of climate change research is to determine if species will be able to persist in a warmer environment. Most studies predict climate change will cause many species to become extinct. However, these predictions are based on experiments where only a single life stage or generation of a species was exposed to predicted future conditions (i.e. shock treatments), and thus overlook the possibility of species adapting or acclimatizing to new environmental conditions over multiple generations. As a result, current projections of species persistence through climate change are likely to overestimate species extinction. In this study, the rate and extent to which adaptation and transgenerational acclimation may allow species to persist through climate change was measured. Marine rotifers, Brachionus plicatilis, were reared for ~75 generations at: i) Optimal temperature (25°C), ii) Optimal temperature (25°C) with weekly sub-lethal shocks (35°C), iii) Maximum temperature (33°C), and iv) Maximum temperature (33°C) with weekly sub-lethal shocks (35°C). Changes in population growth rates and fitness were assessed weekly through rotifer density, adult size and aerobic performance (respiration rate). There was no adaptation observed, but there was evidence of transgenerational acclimation. However, populations were unable to acclimate when exposed to high temperature shocks. This study shows that acclimation through the selection of thermally tolerant individuals can occur over multiple generations in a thermally stable environment, as seen by a reversible increase in aerobic performance, and thus species with short life cycles may be better able to keep up with the pace of climate change. This multi-generational study can enhance our understanding of the rate and extent in which transgenerational acclimation may allow species to persist through climate change. These estimates can then be incorporated into models to improve projections of survival through climate change of species with longer lifespans.

En conditions de stress biotiques et abiotiques la production de plusieurs espèces réactives de l’oxygène (ERO) dans différents compartiments spécialisés de la cellule végétale est inévitable. L’oxygène singulet (1O2) a été identifié comme la principale ERO produite dans le chloroplaste au cours d’un stress lumineux. Cette ERO est très réactive et a une durée de vie courte d’environ 3 s dans les tissus biologiques, ce qui amène à penser que l’oxygène singulet agit principalement par cytotoxicité. Cependant, il a été récemment établi que l’oxygène singulet fonctionne aussi comme une molécule signal impliquée dans la signalisation rétrograde chloroplaste-noyau conduisant soit à la mort cellulaire programmée, soit à l’acclimatation. En raison des propriétés particulières de l’oxygène singulet, il est peu probable que cette ERO voyage en dehors du chloroplaste pour induire des changements d’expression de gènes nucléaires. Une possibilité est que l’oxygène singulet agisse via des médiateurs. Nous avons identifié un produit d’oxydation du β-carotène, le dihydroactinidiolide (dhA), comme intermédiaire dans la voie de signalisation de l’oxygène singulet, qui agit d’une manière similaire à un autre produit d’oxydation du β-carotène, le β-cyclocitral, précédemment identifié comme intermédiaire dans la voie de signalisation de l’oxygène singulet. Nous avons aussi mis en évidence le rôle dans la voie de signalisation régulée par le β-cyclocitral de la protéine MBS1 (METHYLENE BLUE SENSITIVITY 1), et montré que la mort cellulaire programmée induite par l’oxygène singulet chez l’Arabidopsis est controllée par une serine-threonine kinase, OXI1 (OXIDATIVE SIGNAL INDUCIBLE 1). / During biotic and abiotic stress conditions, the production of several reactive oxygen species (ROS) at different specialized compartments of the cell is inevitable. Singlet oxygen (1O2) was identified to be the predominant ROS produced in the chloroplast during high light stress. This molecule is highly reactive, with a short life time of about 3 µs in biological tissues. Such properties make believe that the predominant effect of 1O2 in plants is cytotoxicity. However, 1O2 has been identified to function as a chloroplast-to-nucleus retrograde signaling molecule, leading to acclimation or programmed cell death (PCD). Cognizant of the properties of 1O2, it is most unlikely to travel directly from the chloroplast to the nucleus to signal changes in nuclear gene expression. One possibility is that 1O2 carries out this signaling function with the help of mediators. We identify a β-carotene oxidation product, dihydroactinidiolide (dhA) as a 1O2 signaling intermediate, which function similarly to the β-carotene oxidation product β-cyclocitral, previously identified to be a mediator of 1O2 plastid-nuclear retrograde signaling in Arabidopsis. We reveal a dependence of the β-cyclocitral-mediated signaling pathway on the MBS1 (METHYLENE BLUE SENSITIVITY 1) protein, and show that Programmed cell death induced by 1O2 is mediated by the serine-threonine kinase, OXI1(OXIDATIVE SIGNAL INDUCIBLE 1).

La régulation de la photosynthèse est cruciale pour les organismes photoautotrophes et est habituellement opérée par la modulation de l'absorption de la lumière ou par la réorientation des électrons vers des puits alternatifs afin de redistribuer l'énergie entre plusieurs voies métaboliques. Parmi les différents mécanismes décrits, le remodelage de l'appareil photosynthétique est crucial dans des conditions de carences nutritives ou de fluctuations de la lumière. Il est bien connu que l'oxyde nitrique (NO) joue un rôle de signalisation dans de nombreuses réponses au stress abiotique, agissant comme second messager et / ou modifiant les protéines cibles par des modifications post-traductionnelles redox. Sa participation a été récemment décrite au cours de la carence en azote chez Chlamydomonas reinhardtii. Ce travail se concentre sur le remodelage de l'appareil photosynthétique lors de la carence en soufre et lors des fluctuations de lumineuses chez Chlamydomonas reinhardtii, avec un intérêt particulier pour la voie de signalisation impliquée dans ces réponses. Tout d'abord, nous avons caractérisé la carence en soufre en conditions d’hétérotrophie ou de photo-autotrophie. En faible lumière ou à l’obscurité, l'inactivation photosynthétique est obtenue grâce à la dégradation spécifique de la Rubisco et du cytochrome b6f et ne se produit qu'en présence de carbone réduit dans le milieu. Nous avons également montré une forte production de NO après le début de la carence, avec des sondes fluorescentes sensibles au NO visualisées par microscopie confocale. Nous fournissons des preuves pharmacologiques que la production de NO intracellulaire régit cette voie de dégradation. En outre, ici, nous fournissons des preuves claires de l’existence d’un circuit régulateur qui contrôle la traduction cytosolique du LHCII en réponse à des changements de quantité de lumière. Ce circuit nécessite la protéine de liaison à l'ARN cytosolique NAB1 pour réprimer la traduction de certains ARNm de LHCII. La nitrosylation spécifique de la Cys-226 diminue l'activité de NAB1 et a été démontrée in vitro et in vivo. La forme moins active et nitrosylée de NAB1 se trouve dans les cellules acclimatées à un apport de lumière limité, ce qui permet l'accumulation de protéines des antennes et la capture efficace de la lumière. En revanche, une intensité lumineuse plus élevée provoque la dénitrosylation de NAB1, activant ainsi la répression de la synthèse des protéines LHCII et diminuant ainsi la pression de la lumière au niveau du PSII. La dénitrosylation de NAB1 est efficacement réalisée par le système thiorédoxine cytosolique in vitro. À notre connaissance, NAB1 est le premier exemple de dénitrosylation induite par un stimulus dans le contexte de l'acclimatation photosynthétique. Dans l’ensemble, nos données suggèrent un rôle pivot pour la signalisation NO dans le contrôle des réponses au stress environnemental. / The regulation of photosynthesis is crucial for photoautotrophic organisms and is usually operated by the modulation of light absorption or by redirection of electrons towards alternative sinks, in order to redistribute energy among several metabolic pathways. Between different mechanisms described, the remodeling of the photosynthetic apparatus is crucial under conditions of nutrient starvation or light fluctuations. It is well known that nitric oxide (NO) plays a signaling role in many abiotic stress responses, acting as a second messenger and/or modifying target proteins through redox post translational modifications. Its involvement has been recently described during nitrogen starvation in Chlamydomonas reinhardtii. This work focuses on the remodeling of the photosynthetic apparatus upon sulfur starvation and light fluctuations in Chlamydomonas reinhardtii, with particular interest for the signaling pathway involved in the responses. First we characterized sulfur starvation under heterotrophy and photo-autotrophy. Photosynthetic inactivation under low light and darkness is achieved through specific degradation of Rubisco and cytochrome b₆f and occurs only in the presence of reduced carbon in the medium. We have also shown a strong NO production after the onset of starvation, with NO-sensitive fluorescence probes visualized by confocal microscopy. We provide pharmacological evidence that intracellular NO production governs this degradation pathway using NO scavengers, NO synthesis inhibitors and NO donors. Furthermore, here, we provide clear evidence for a regulatory circuit that controls cytosolic LHCII translation in response to light quantity changes. This circuit requires the cytosolic RNA-binding protein NAB1 to repress translation of certain LHCII mRNAs. Specific nitrosylation of Cys-226 decreases NAB1 activity and could be demonstrated in vitro and in vivo. The less active, nitrosylated form of NAB1 is found in cells acclimated to limiting light supply, which permits accumulation of light harvesting proteins and efficient light capture. In contrast, elevated light supply causes NAB1 denitrosylation, thereby activating the repression of light-harvesting protein synthesis and decreasing the light pressure at the level of PSII. Denitrosylation of NAB1 is efficiently performed by the cytosolic thioredoxin system in vitro. To our knowledge, NAB1 is the first example of stimulus-induced denitrosylation in the context of photosynthetic acclimation. Taken together, our data suggest a pivotal role for NO-signaling in the control of environmental stress responses.

No description available.

Diploma thesis’s aim was to determine Rubisco activity and its content in sunny and shaded needles of Norway spruce (Picea abies [L.] Karst.) and confirm or refuse acclimation on Rubisco enzyme level. Samples were taken on the Experimental ecology station Czech Academy of Sciences at Bílý Kříž (Beskydy Mountains) where needles were cultivated in two cultivation spheres with different concetrations CO2. One cultivation sphere contains atmosphere with ambient (A) concentration CO2 (350 mol CO2 mol-1) and the other contains atmosphere with elevated (E) concentration CO2 (700 mol CO2 mol-1). Rubisco activities were determinated spectrophotometric, Rubisco content was determined by SDS-PAGE method. Samples were taken in the modele of June and in the end of September. Elevated concetration CO2 did not have significant influence on Rubisco activity. Whereas different exposition had significant influence on Rubisco activity in June, when was found lower Rubisco activity in shaded needles than in sunny needles. In September were not find significant differences in Rubisco activity beetwen sunny and shaded needles. We did not find statistically significant differences in Rubisco content between A and E needles in June. Incontrary, we found about 34 % lower Rubisco content in E needles than in A needles, which confirms acclimation on Rubisco enzyme level. In September Rubisco content was several time higher than in June, which evidences the long term building photosynthetic apparatus in coniferous trees.

This diploma thesis examines influence of content of leaf nitrogen and non-structural carbohydrates on Rubisco activity and its content under impact of ambient (A = 385 µmolCO2 mol-1) and elevated (E = 700 µmolCO2 mol-1) concentrations of carbon dioxide in needles of Norway spruce (Picea abies L.). The Rubisco activity was determined spectrophotometrically, the Rubisco content by using SDS-PAGE, the content of non-structural carbohydrates by using the anthron method and total leaf nitrogen was determined by using the Kjeldahl method. The Rubisco activity in needles of Norway spruce did not show acclimation on elevated concentration of carbon dioxide, but the activity was elevated concentration of carbon dioxide stimulated during the growing season. The acclimation was proved by Rubisco content, its content was significantly lower in needles cultivated under elevated carbon dioxide. Content of total leaf nitrogen was statistically significantly lower in needles of Norway spruce cultivated under elevated carbon dioxide then in needles cultivated under ambient concentration of carbon dioxide. On the contrary, the content of non-structural carbohydrates was significantly higher in needles cultivated under elevated concentration of carbon dioxide then in variant A. Seasonal changes of Rubisco content depended on content of non-structural carbohydrates, the Rubisco content decreased with increasing content of non-structural carbohydrates. No dependence was detected between seasonal changes of the total leaf content and the Rubisco content.