Assessing the sensitivity of bivalve populations to global warming using an individual‐based modelling approach

Climate change exposes benthic species populations in coastal ecosystems to a combination of different stressors (e.g., warming, acidification and eutrophication), threatening the sustainability of the ecological functions they provide. Thermal stress appears to be one of the strongest drivers impacting marine ecosystems, acting across a wide range of scales, from individual metabolic performances to geographic distribution of populations. Accounting for and integrating the response of species functional traits to thermal stress is therefore a necessary step in predicting how populations will respond to the warming expected in coming decades. Here, we developed an individual‐based population model using a mechanistic formulation of metabolic processes within the framework of the dynamic energy budget theory. Through a large number of simulations, we assessed the sensitivity of population growth potential to thermal stress and food conditions based on a climate projection scenario (Representative Concentration Pathway; RCP8.5: no reduction of greenhouse gas emissions). We focused on three bivalve species with contrasting thermal tolerance ranges and distinct distribution ranges along 5,000 km of coastline in the NE Atlantic: the Pacific oyster (Magallana gigas), and two mussel species: Mytilus edulis and Mytilus galloprovincialis. Our results suggest substantial and contrasting changes within species depending on local temperature and food concentration. Reproductive phenology appeared to be a core process driving the responses of the populations, and these patterns were closely related to species thermal tolerances. The nonlinear relationship we found between individual life‐history traits and response at the population level emphasizes the need to consider the interactions resulting from upscaling across different levels of biological organisation. These results underline the importance of a process‐based understanding of benthic population response to seawater warming, which will be necessary for forward planning of resource management and strategies for conservation and adaptation to environmental changes.     

Effective tolerance based on resource reallocation is a virus‐specific defence in Arabidopsis thaliana

Plant viruses often harm their hosts, which have developed mechanisms to prevent or minimize the effects of virus infection. Resistance and tolerance are the two main plant defences to pathogens. Although resistance to plant viruses has been studied extensively, tolerance has received much less attention. Theory predicts that tolerance to low‐virulent parasites would be achieved through resource reallocation from growth to reproduction, whereas tolerance to high‐virulent parasites would be attained through shortening of the pre‐reproductive period. We have shown previously that the tolerance of Arabidopsis thaliana to Cucumber mosaic virus (CMV), a relatively low‐virulent virus in this host, accords to these predictions. However, whether other viruses trigger the same response, and how A. thaliana copes with highly virulent virus infections remains unexplored. To address these questions, we challenged six A. thaliana wild genotypes with five viruses with different genomic structures, life histories and transmission modes. In these plants, we quantified virus multiplication, virulence, and the effects of infection on plant growth and reproduction, and on the developmental schedule. Our results indicate that virus multiplication varies according to the virus × host genotype interaction. Conversely, effective tolerance is observed only on CMV infection, and is associated with resource reallocation from growth to reproduction. Tolerance to the other viruses is observed only in specific host–virus combinations and, at odds with theoretical predictions, is linked to longer pre‐reproductive periods. These findings only partially agree with theoretical predictions, and contribute to a better understanding of pathogenic processes in plant–virus interactions.     

Engineering heat tolerance in potato by temperature‐dependent expression of a specific allele of HEAT‐SHOCK COGNATE 70

For many commercial potato cultivars, tuber yield is optimal at average daytime temperatures in the range of 14–22 °C. Further rises in ambient temperature can reduce or completely inhibit potato tuber production, with damaging consequences for both producer and consumer. The aim of this study was to use a genetic screen based on a model tuberization assay to identify quantitative trait loci (QTL) associated with enhanced tuber yield. A candidate gene encoding HSc70 was identified within one of the three QTL intervals associated with elevated yield in a Phureja–Tuberosum hybrid diploid potato population (06H1). A particular HSc70 allelic variant was linked to elevated yield in the 06H1 progeny. Expression of this allelic variant was much higher than other alleles, particularly on exposure to moderately elevated temperature. Transient expression of this allele in Nicotiana benthamiana resulted in significantly enhanced tolerance to elevated temperature. An TA repeat element was present in the promoter of this allele, but not in other HSc70 alleles identified in the population. Expression of the HSc70 allelic variant under its native promoter in the potato cultivar Desiree resulted in enhanced HSc70 expression at elevated temperature. This was reflected in greater tolerance to heat stress as determined by improved yield under moderately elevated temperature in a model nodal cutting tuberization system and in plants grown from stem cuttings. Our results identify HSc70 expression level as a significant factor influencing yield stability under moderately elevated temperature and identify specific allelic variants of HSc70 for the induction of thermotolerance via conventional introgression or molecular breeding approaches.     

PeCHYR1, a ubiquitin E3 ligase from Populus euphratica,enhances drought tolerance via ABA‐induced stomatal closure by ROS production in Populus

Drought, a primary abiotic stress, seriously affects plant growth and productivity. Stomata play a vital role in regulating gas exchange and drought adaptation. However, limited knowledge exists of the molecular mechanisms underlying stomatal movement in trees. Here, PeCHYR1, a ubiquitin E3 ligase, was isolated from Populus euphratica, a model of stress adaptation in forest trees. PeCHYR1 was preferentially expressed in young leaves and was significantly induced by ABA (abscisic acid) and dehydration treatments. To study the potential biological functions of PeCHYR1, transgenic poplar 84K (Populus alba × Populus glandulosa) plants overexpressing PeCHYR1 were generated. PeCHYR1 overexpression significantly enhanced H₂O₂ production and reduced stomatal aperture. Transgenic lines exhibited increased sensitivity to exogenous ABA and greater drought tolerance than that of WT (wild‐type) controls. Moreover, up‐regulation of PeCHYR1 promoted stomatal closure and decreased transpiration, resulting in strongly elevated WUE (water use efficiency). When exposed to drought stress, transgenic poplar maintained higher photosynthetic activity and biomass accumulation. Taken together, these results suggest that PeCHYR1 plays a crucial role in enhancing drought tolerance via ABA‐induced stomatal closure caused by hydrogen peroxide (H₂O₂) production in transgenic poplar plants.     

CIC对高脂膳食大鼠肝脏氧化应激的影响

目的:研究慢性间断性冷暴露(mild chronic intermittent cold exposure,CIC)对高脂膳食大鼠肝脏氧化应激的影响。方法:轻度CIC已被广泛用于建立冷适应研究的动物模型。本研究通过将大鼠暴露于温和的CIC和/或高脂膳食4w,检测肛温、体重、肝脏重量、ATP和活性氧(ROS)的水平,Western blot检测冷诱导RNA结合蛋白(cold inducible RNA binding protein,Cirbp)和硫氧还蛋白(Thioredoxin,TRX)的蛋白表达。结果:同对照组相比,高脂膳食组体重显著增加,血清和肝脏ROS水平显著升高,ATP水平没有显著影响。同对照组相比,CIC暴露1w后大鼠肛温显著降低,而2w、3w和4w周肛温没有显著差异,ROS水平无显著差异,但ATP水平显著升高;Cirbp和TRX的表达显著升高。同常温高脂膳食组相比,CIC暴露4w后,大鼠体重显著降低,ROS水平无显著差异,而ATP水平显著升高;Cirbp和TRX的表达水平显著升高。这些结果均提示冷适应增强了高脂膳食大鼠肝脏的抗氧化水平,可能是由于冷适应后Cirbp表达升高,继而调控其下游的抗氧化蛋白TRX的表达增加,从而清除ROS的缘故。结论:CIC暴露诱导的冷适应可保护肝脏免于高脂膳食诱导的氧化应激。     

Adaptation to fluctuations in temperature by nine species of bacteria

Rapid environmental fluctuations are ubiquitous in the wild, yet majority of experimental studies mostly consider effects of slow fluctuations on organism. To test the evolutionary consequences of fast fluctuations, we conducted nine independent experimental evolution experiments with bacteria. Experimental conditions were same for all species, and we allowed them to evolve either in fluctuating temperature alternating rapidly between 20°C and 40°C or at constant 30°C temperature. After experimental evolution, we tested the performance of the clones in both rapid fluctuation and in constant environments (20°C, 30°C and 40°C). Results from experiments on these nine species were combined meta‐analytically. We found that overall the clones evolved in the fluctuating environment had evolved better efficiency in tolerating fluctuations (i.e., they had higher yield in fluctuating conditions) than the clones evolved in the constant environment. However, we did not find any evidence that fluctuation‐adapted clones would have evolved better tolerance to any measured constant environments (20°C, 30°C, and 40°C). Our results back up recent empirical findings reporting that it is hard to predict adaptations to fast fluctuations using tolerance curves.     

Low acclimation capacity of narrow‐ranging thermal specialists exposes susceptibility to global climate change

Thermal acclimation is hypothesized to offer a selective advantage in seasonal habitats and may underlie disparities in geographic range size among closely‐related species with similar ecologies. Understanding this relationship is also critical for identifying species that are more sensitive to warming climates. Here, we study North American plethodontid salamanders to investigate whether acclimation ability is associated with species’ latitudinal extents and the thermal range of the environments they inhabit. We quantified variation in thermal physiology by measuring standard metabolic rate (SMR) at different test and acclimation temperatures for 16 species of salamanders with varying latitudinal extents. A phylogenetically‐controlled Markov chain Monte Carlo generalized linear mixed model (MCMCglmm) was then employed to determine whether there are differences in SMR between wide‐ and narrow‐ranging species at different acclimation temperatures. In addition, we tested for a relationship between the acclimation ability of species and the environmental temperature ranges they inhabit. Further, we investigated if there is a trade‐off between critical thermal maximum (CTMax) and thermal acclimation ability. MCMCglmm results show a significant difference in acclimation ability between wide and narrow‐ranging temperate salamanders. Salamanders with wide latitudinal distributions maintain or slightly increase SMR when subjected to higher test and acclimation temperatures, whereas several narrow‐ranging species show significant metabolic depression. We also found significant, positive relationships between acclimation ability and environmental thermal range, and between acclimation ability and CTMax. Wide‐ranging salamander species exhibit a greater capacity for thermal acclimation than narrow‐ranging species, suggesting that selection for acclimation ability may have been a key factor enabling geographic expansion into areas with greater thermal variability. Further, given that narrow‐ranging salamanders are found to have both poor acclimation ability and lower tolerance to warm temperatures, they are likely to be more susceptible to environmental warming associated with anthropogenic climate change.     

Enhanced immunization techniques to obtain highly specific monoclonal antibodies

Despite fast advances in genomics and proteomics, monoclonal antibodies (mAbs) are still a valuable tool for areas such as the evolution of basic research in stem cells and cancer, for immunophenotyping cell populations, diagnosing and prognosis of diseases, and for immunotherapy. To summarize different subtractive immunization approaches successfully used for the production of highly specific antibodies, we identified scientific articles in NCBI PubMed using the following search terms: subtractive immunization, monoclonal antibody, tolerization, neonatal, high-zone tolerance, masking immunization. Patent records were also consulted. From the list of results, we included all available reports, from 1985 to present, that used any enhanced immunization technique to produce either polyclonal or monoclonal antibodies. Our examination yielded direct evidence that these enhanced immunization techniques are efficient in obtaining specific antibodies to rare epitopes, with different applications, such as to identify food contaminants or tumor cells.     

Tree hydraulic traits are coordinated and strongly linked to climate‐of‐origin across a rainfall gradient

Plant hydraulic traits capture the impacts of drought stress on plant function, yet vegetation models lack sufficient information regarding trait coordination and variation with climate‐of‐origin across species. Here, we investigated key hydraulic and carbon economy traits of 12 woody species in Australia from a broad climatic gradient, with the aim of identifying the coordination among these traits and the role of climate in shaping cross‐species trait variation. The influence of environmental variation was minimized by a common garden approach, allowing us to factor out the influence of environment on phenotypic variation across species. We found that hydraulic traits (leaf turgor loss point, stomatal sensitivity to drought [P_gs], xylem vulnerability to cavitation [P_x], and branch capacitance [C_branch]) were highly coordinated across species and strongly related to rainfall and aridity in the species native distributional range. In addition, trade‐offs between drought tolerance and plant growth rate were observed across species. Collectively, these results provide critical insight into the coordination among hydraulic traits in modulating drought adaptation and will significantly advance our ability to predict drought vulnerability in these dominant trees species.