Acclimatation

Résumé

vignette|Les grandes découvertes ont favorisé l'acclimatation de nombreuses espèces végétales et animales américaines et asiatiques (maïs, piment, pomme de terre, canne à sucre, cacao, oiseaux exotiques, bétail...) qui, à l'issue d'une lente acclimatation, sont passées de l'expérimentation à la domestication, du jardin ou de la ménagerie aux champs.Exemple de la tomate : 1. Pérou, centre de diversification, 2. Mexique : premier centre de domestication, 3. Europe : deuxième centre de domestication, 4. États-Unis : troisième centre de domestication. vignette|Originaire d'Amérique du Nord, le raton laveur a été introduit pour la dernière fois dans les années 1930 en Europe où il s'est parfaitement acclimaté puis naturalisé et a proliféré en l'absence de ses prédateurs naturels (martre d’Amérique, lynx roux, puma, coyote). Considéré comme une menace pour la biodiversité, il a été classé par le Conseil de l’Europe comme espèce exotique envahissante dont l’éradi

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https://fr.wikipedia.org/wiki/Acclimatation

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Fast and pervasive transcriptomic resilience and acclimation of extremely heat-tolerant coral holobionts from the northern Red Sea

Maoz Fine, Anders Meibom, Romain Savary

Corals from the northern Red Sea and Gulf of Aqaba exhibit extreme thermal tolerance. To examine the underlying gene expression dynamics, we exposed Stylophora pistillata from the Gulf of Aqaba to short-term (hours) and long-term (weeks) heat stress with peak seawater temperatures ranging from their maximum monthly mean of 27 degrees C (baseline) to 29.5 degrees C, 32 degrees C, and 34.5 degrees C. Corals were sampled at the end of the heat stress as well as after a recovery period at baseline temperature. Changes in coral host and symbiotic algal gene expression were determined via RNA-sequencing (RNA-Seq). Shifts in coral microbiome composition were detected by complementary DNA (cDNA)-based 16S ribosomal RNA (rRNA) gene sequencing. In all experiments up to 32 degrees C, RNA-Seq revealed fast and pervasive changes in gene expression, primarily in the coral host, followed by a return to baseline gene expression for the majority of coral (>94%) and algal (>71%) genes during recovery. At 34.5 degrees C, large differences in gene expression were observed with minimal recovery, high coral mortality, and a microbiome dominated by opportunistic bacteria (including Vibrio species), indicating that a lethal temperature threshold had been crossed. Our results show that the S. pistillata holobiont can mount a rapid and pervasive gene expression response contingent on the amplitude and duration of the thermal stress. We propose that the transcriptomic resilience and transcriptomic acclimation observed are key to the extraordinary thermal tolerance of this holobiont and, by inference, of other northern Red Sea coral holobionts, up to seawater temperatures of at least 32 degrees C, that is, 5 degrees C above their current maximum monthly mean.

2021

Chargement

Comparison of two carbon-nitrogen regulatory models calibrated with mesocosm data

Shubham Krishna

Marine phytoplankton can regulate their stoichiometric composition in response to variations in the availability of nutrients, light and the pH of seawater. Varying elemental composition of photoautotrophs affects several important ecological and biogeochemical processes, e.g., primary and export production, nutrient cycling, calcification, and grazing. Here we compare two plankton ecosystem models that consider regulatory mechanisms of cellular carbon and nitrogen, driving the physiological acclimation of photoautotrophs. The Carbon:Nitrogen Regulated Ecosystem Model (CN-REcoM) and the optimality-based model (OBM) differ in their representation of phytoplankton dynamics, i.e. nutrient acquisition, synthesis of chlorophyll a, and growth. All other model compartments (zooplankton, detritus, dissolved inorganic and organic matter) and processes (grazing, aggregation, remineralisation) remain identical in both models. We assess the skills of the two models against data from an ocean acidification mesocosm experiment with three CO2 treatments. Neither model accounts for any carbon dioxide (CO2) effects explicitly. Instead, we assimilate data of the different CO2 treatments separately into the models. Thereby we aim at identifying optimal model parameter values that might correlate with differences in CO2 conditions. For the OBM, optimal parameter estimates of Q(min) (subsistence N:C ratio) and V-C(0) (maximum potential photosynthesis rate of photoautotrophs) turned out to be higher for mesocosms exposed to high CO2 compared to those with low CO2 concentrations. By contrast, a similar correlation is not observed for the CN-REcoM. A possible physiological interpretation of higher estimates of Q(min), and V-C(0) according to the OBM is that phytoplankton may experience environmental stress under more acidic conditions, and hence must invest more energy/resources for maintaining basic cellular functions. Our data assimilation reveals that the parameters of the OBM are better constrained by the data than those of the CN-REcoM. Furthermore, the OBM is better able than CN-REcoM to reproduce data that were not used for parameter optimization.

2019

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Despite worldwide reports of high tree mortality, growing evidence indicates that many tree species are well adapted to survive repeated dry spells. The drought resilience of trees is related to their phenotypic plasticity and ecotypic differentiation. Whether these two mechanisms act at the same organisational level of a tree and involve similar plant traits is still unknown. We assessed phenotypic plasticity and ecotypic differentiation across four populations of Pinus sylvestris and Pinus nigra seedlings grown for 3 years under a recurrent summer drought treatment or well-watered control conditions in a common garden. We measured the response to the summer drought treatment of a total of 26 traits including shoot and needle morphology, needle anatomy and foliar macronutrients, and related the traits to the growing season water deficit (GSWD) at the location of the seed origin. Foliar phenotypic plasticity in response to recurrent summer drought was surprisingly low, with the needle length and the fraction of mesophyll and phloem tissue adjusting to some extent. In comparison, shoot morphological traits were much more plastic in both species with predominant responses to the summer drought stress including shorter and less numerous apical and lateral shoots. These three traits were also correlated with GSWD at the seed origin, indicating local adaptation. In contrast, between-population variation of foliar morphological and anatomical traits, and macronutrients were mostly unrelated to the GSWD at the seed origin. Consequently, phenotypic plasticity and ecotypic differentiation occurred at the same level of organisation and in the same plant traits, that is, shoot morphology. This combination of plasticity and ecotypic differentiation allowed P. sylvestris and P. nigra seedlings to rapidly acclimate to recurrent and long-lasting dry spells. Synthesis. Pinus sylvestris and P. nigra seedlings showed considerable ecotypic differentiation and phenotypic plasticity of shoot morphological traits, and not foliar traits. Acclimation to recurrent severe summer drought was achieved by reducing shoot growth.

WILEY2021

Chargement

Comparison of two carbon-nitrogen regulatory models calibrated with mesocosm data

Shubham Krishna

2019

WILEY2021