Elevated Temperature and CO2 Stimulate Late-Season Photosynthesis But Impair Cold Hardening in Pine

Rising global temperature and CO₂ levels may sustain late-season net photosynthesis of evergreen conifers but could also impair the development of cold hardiness. Our study investigated how elevated temperature, and the combination of elevated temperature with elevated CO₂, affected photosynthetic rates, leaf carbohydrates, freezing tolerance, and proteins involved in photosynthesis and cold hardening in Eastern white pine (Pinus strobus). We designed an experiment where control seedlings were acclimated to long photoperiod (day/night 14/10 h), warm temperature (22°C/15°C), and either ambient (400 μL L⁻¹) or elevated (800 μmol mol⁻¹) CO₂, and then shifted seedlings to growth conditions with short photoperiod (8/16 h) and low temperature/ambient CO₂ (LTAC), elevated temperature/ambient CO₂ (ETAC), or elevated temperature/elevated CO₂ (ETEC). Exposure to LTAC induced down-regulation of photosynthesis, development of sustained nonphotochemical quenching, accumulation of soluble carbohydrates, expression of a 16-kD dehydrin absent under long photoperiod, and increased freezing tolerance. In ETAC seedlings, photosynthesis was not down-regulated, while accumulation of soluble carbohydrates, dehydrin expression, and freezing tolerance were impaired. ETEC seedlings revealed increased photosynthesis and improved water use efficiency but impaired dehydrin expression and freezing tolerance similar to ETAC seedlings. Sixteen-kilodalton dehydrin expression strongly correlated with increases in freezing tolerance, suggesting its involvement in the development of cold hardiness in P. strobus. Our findings suggest that exposure to elevated temperature and CO₂ during autumn can delay down-regulation of photosynthesis and stimulate late-season net photosynthesis in P. strobus seedlings. However, this comes at the cost of impaired freezing tolerance. Elevated temperature and CO₂ also impaired freezing tolerance. However, unless the frequency and timing of extreme low-temperature events changes, this is unlikely to increase risk of freezing damage in P. strobus seedlings.Land surface temperature is increasing, particularly in the northern hemisphere (IPCC, 2014), which is dominated by boreal and temperate forests. At higher latitudes, trees rely on temperature and photoperiod cues to detect changing seasons and to trigger cessation of growth and cold hardening during the autumn (Ensminger et al., 2015). For boreal and temperate evergreen conifers, cold hardening involves changes in carbohydrate metabolism, down-regulation of photosynthesis, accumulation of cryoprotective metabolites, and development of freezing tolerance (Crosatti et al., 2013; Ensminger et al., 2015). These processes minimize freezing damage and enable conifers to endure winter stresses. However, rising temperatures result in asynchronous phasing of temperature and photoperiod characterized by delayed arrival of first frosts (McMahon et al., 2010), which may impact the onset and development of cold hardening during autumn.Short photoperiod induces the cessation of growth in many tree species (Downs and Borthwick, 1956; Heide, 1974; Repo et al., 2000; Böhlenius et al., 2006). As a consequence, carbon demand in sink tissue decreases toward the end of the growing season, and the bulk of photoassimilate is translocated from source tissues to storage tissues (Hansen and Beck, 1994; Oleksyn et al., 2000). In addition, cryoprotective soluble sugars, including sucrose, raffinose, and pinitol, accumulate in leaf tissues to enhance freezing tolerance (Strimbeck et al., 2008; Angelcheva et al., 2014). Thus, by winter, leaf nonstructural carbohydrates are mainly comprised of mono- and oligosaccharides, and only minimal levels of starch remain (Hansen and Beck, 1994; Strimbeck et al., 2008). The concurrent decrease of photoassimilate and demand for metabolites that occur during the cessation of growth also impacts the citric acid cycle that mediates between photosynthesis, respiration, and protein synthesis. The citric acid cycle generates NADH to fuel ATP synthesis via mitochondrial electron transport, as well as amino acid precursors (Shi et al., 2015). In C3 plants, the enzyme phosphoenolpyruvate carboxylase (PEPC) converts phosphoenolpyruvate to oxaloacetic acid in order to supplement the flow of metabolites to the citric acid cycle and thus controls the regulation of respiration and photosynthate partitioning (O’Leary et al., 2011).Cessation of growth, low temperature, and presumably short photoperiod decrease the metabolic sink for photoassimilates, resulting in harmful excess light energy (Öquist and Huner, 2003; Ensminger et al., 2006) and increased generation of reactive oxygen species (Adams et al., 2004). During autumn and the development of cold hardiness, conifers reconfigure the photosynthetic apparatus in order to avoid formation of excess light and reactive oxygen species. This involves a decrease in chlorophylls and PSII reaction center core protein D1 (Ottander et al., 1995; Ensminger et al., 2004; Verhoeven et al., 2009), as well as aggregation of light-harvesting complex proteins (Ottander et al., 1995; Busch et al., 2007). Additionally, photoprotective carotenoid pigments accumulate in leaves, especially the xanthophylls, zeaxanthin, and lutein that contribute to nonphotochemical quenching (NPQ) via thermal dissipation of excess light energy (Busch et al., 2007; Verhoeven et al., 2009; Demmig-Adams et al., 2012). Prolonged exposure to low temperature induces sustained nonphotochemical quenching (NPQ_S), where zeaxanthin constitutively dissipates excess light energy (Ensminger et al., 2004; Demmig-Adams et al., 2012; Fréchette et al., 2015).In conifers, freezing tolerance is initiated during early autumn in response to decreasing photoperiod (Rostad et al., 2006; Chang et al., 2015) and continues to develop through late autumn in response to the combination of short photoperiod and low temperature (Strimbeck and Schaberg, 2009; Chang et al., 2015). In addition to changes in carbohydrate content, freezing tolerance also involves the expression of specific dehydrins (Close, 1997; Kjellsen et al., 2013). Members of the dehydrin protein family are involved in responses to osmotic, salt, and freezing stress (Close, 1996). Dehydrins have been associated with improved freezing tolerance in many species including spinach (Kaye et al., 1998), strawberry (Houde et al., 2004), cucumber (Yin et al., 2006), peach (Wisniewski et al., 1999), birch (Puhakainen et al., 2004), and spruce (Kjellsen et al., 2013). In angiosperms, a characteristic Lys-rich dehydrin motif known as the K-segment interacts with lipids to facilitate membrane binding (Koag et al., 2003; Eriksson et al., 2011). Several in vitro studies have demonstrated dehydrin functions including prevention of aggregation and unfolding of enzymes (using Vitis riparia; Hughes and Graether, 2011), radical scavenging (using Citrus unshiu; Hara et al., 2004), and suppression of ice crystal formation (using Prunus persica; Wisniewski et al., 1999). To date, dehydrin functions have not been demonstrated in planta.Rising temperatures since the mid-twentieth century have delayed the onset of autumn dormancy and increased length of the growing season in forests across the northern hemisphere (Boisvenue and Running, 2006; Piao et al., 2007; McMahon et al., 2010). Studies have shown that elevated temperatures ranging from +4°C to +20°C above ambient can delay down-regulation of photosynthesis in several evergreen conifers. Consistent findings were apparent among climate-controlled chamber studies exposing Pinus strobus seedlings to a sudden shift in temperature and/or photoperiod (Fréchette et al., 2016), as well as chamber studies exposing Picea abies seedlings to simulated autumn conditions using a gradient of decreasing temperature and photoperiod (Stinziano et al., 2015). Similar findings were also demonstrated in open-top chamber experiments exposing mature Pinus sylvestris to a gradient of decreasing temperature and natural photoperiod (Wang, 1996). Elevated temperature (+4°C above ambient) also impaired cold hardening in Pseudotsuga menziesii seedlings (Guak et al., 1998) and mature P. sylvestris (Repo et al., 1996) exposed to a decreasing gradient of temperature and natural photoperiod using open-top chambers. In contrast, a recent study showed that smaller temperature increments (+1.5°C to +3°C) applied using infrared heaters did not delay down-regulation of photosynthesis or impair freezing tolerance in field-grown P. strobus seedlings that were acclimated to larger diurnal and seasonal temperature variations (Chang et al., 2015). For many tree species, photoperiod determines cessation of growth (Tanino et al., 2010; Petterle et al., 2013), length of the growing season (Bauerle et al., 2012), and development of cold hardiness (Welling et al., 1997; Li et al., 2003; Rostad et al., 2006). However, the effects of climate warming on tree phenology are complex and can be unpredictable due to species- and provenance-specific differences in sensitivity to photoperiod and temperature cues (Körner and Basler, 2010; Basler and Körner, 2012; Basler and Körner, 2014).The effect of elevated CO₂ further increases uncertainties in the response of trees to warmer climate. Similar to warmer temperature, elevated CO₂ may also delay the down-regulation of photosynthesis in evergreens and extend the length of the growing season, as demonstrated in mature P. sylvestris (Wang, 1996). Elevated CO₂ increases carbon assimilation (Curtis and Wang, 1998; Ainsworth and Long, 2005) and biomass production (Ainsworth and Long, 2005) during the growing season. The effects could continue during the autumn if dormancy or growth cessation is delayed, which suggests that elevated CO₂ may increase annual carbon uptake. However, long-term exposure to elevated CO₂ can also down-regulate photosynthesis during the growing season (Ainsworth and Long, 2005). Prior studies that have attempted to determine the impact of a combination of elevated CO₂ and/or temperature on cold hardening in evergreens have largely focused on freezing tolerance, with contrasting results. Open-top chamber experiments showed that a combination of elevated temperature and CO₂ both delayed and impaired freezing tolerance of P. menziesii seedlings (Guak et al., 1998) and evergreen broadleaf Eucalyptus pauciflora seedlings (Loveys et al., 2006) but did not affect freezing tolerance of mature P. sylvestris (Repo et al., 1996). A recent field experiment examining mature trees revealed that Larix decidua, but not Pinus mugo, exhibited enhanced freezing damage following six years of exposure to combined soil warming and elevated CO₂ (Rixen et al., 2012). In contrast, a climate-controlled study showed that exposure to elevated CO₂ advanced the date of bud set and improved freezing tolerance in Picea mariana seedlings (Bigras and Bertrand, 2006). In a second study on similar seedlings conducted by the same authors, exposure of trees to elevated CO₂ also enhanced freezing tolerance but impaired the accumulation of sucrose and raffinose (Bertrand and Bigras, 2006). These previous experiments used experimental conditions where temperature and photoperiod gradually decreased. While this approach aims to mimic natural conditions, it is difficult to distinguish specific responses to either photoperiod or temperature. Because of the contrasting findings from previous studies, we designed an experiment aiming to separate the effects of photoperiod, temperature, and CO₂ on a wide range of parameters that are involved in cold hardening in conifers.Our study aimed to determine (1) how induction and development of the cold hardening process is affected by a shift from long to short photoperiod under warm conditions and (2) how the combination of warm air temperature and elevated CO₂ affects photoperiod-induced cold hardening processes in Eastern white pine (P. strobus). To assess the development of cold hardening, we measured photosynthetic rates, changes in leaf carbohydrates, freezing tolerance, and proteins involved in photosynthesis and cold hardening over 36 d. Assuming that both low temperature and short photoperiod cues are required to induce cold hardening in conifers, we hypothesized that warm temperature and the combination of warm temperature and elevated CO₂ would prevent seedlings growing under autumn photoperiod from down-regulating photosynthesis. We further hypothesized that warm temperature and the combination of warm temperature and elevated CO₂ would impair the development of freezing tolerance, due to a lack of adequate phasing of the low temperature and short photoperiod signals.     

Confined Fe2VO4⊂Nitrogen‐Doped Carbon Nanowires with Internal Void Space for High‐Rate and Ultrastable Potassium‐Ion Storage

Developing low‐cost, high‐capacity, high‐rate, and robust earth‐abundant electrode materials for energy storage is critical for the practical and scalable application of advanced battery technologies. Herein, the first example of synthesizing 1D peapod‐like bimetallic Fe₂VO₄ nanorods confined in N‐doped carbon porous nanowires with internal void space (Fe₂VO₄?NC nanopeapods) as a high‐capacity and stable anode material for potassium‐ion batteries (KIBs) is reported. The peapod‐like Fe₂VO₄?NC nanopeapod heterostructures with interior void space and external carbon shell efficiently prevent the aggregation of the active materials, facilitate fast transportation of electrons and ions, and accommodate volume variation during the cycling process, which substantially boosts the rate and cycling performance of Fe₂VO₄. The Fe₂VO₄?NC electrode exhibits high reversible specific depotassiation capacity of 380 mAh g^?1 at 100 mA g^?1 after 60 cycles and remarkable rate capability as well as long cycling stability with a high capacity of 196 mAh g^?1 at 4 A g^?1 after 2300 cycles. The first‐principles calculations reveal that Fe₂VO₄?NC nanopeapods have high ionic/electronic conductivity characteristics and low diffusion barriers for K⁺‐intercalation. This study opens up new way for investigating high‐capacity metal oxide as high‐rate and robust electrode materials for KIBs.     

Severe diarrhoea caused by Aeromonas veronii biovar sobria in a patient with metastasised GIST.

This report describes the isolation of Aeromonas veronii biovar sobria as the causative enteropathogen of diarrhoea in an oncological patient after failure of detection of other infectious agents. The case points out the severe and long course of the infection, the diagnostic dilemma, and the prompt recovery after antibiotic treatment.     

Reduction of IL-2 fragmentation during manufacturing of a novel immunocytokine by DoE process optimization

Interleukin-2 (IL-2) is a potent molecule in cancer therapy. Clinical application, however, is limited due to its strong side effects during the treatment. We developed an IL-2 variant (IL-2v) immunocytokine to circumvent the drawbacks of the current IL-2 therapy. During the production of the IL-2v immunocytokine in Chinese hamster ovary (CHO) cells, molecules with fragmented IL-2v and therefore reduced cytokine activity can be observed. To control product fragmentation different production process conditions were investigated. By shifting temperature or pH after the cell growth phase to lower values, fragmented species can be reduced from 10% to 12% to about 4%. However, with the adopted process conditions, the effective titer is decreased concomitantly. Moreover, fermentation length and inoculation cell density are parameters to adjust fragmentation and effective titer. A suitable method for efficient process optimization is the design of experiment approach. With this procedure, novel optimal values for temperature, pH value, harvest day, and inoculation cell densities were proposed and tested subsequently. In comparison to the former process, the improved process reduces fragmentation by 66% while keeping the effective titer comparable. In summary, these findings will help to control fragmentation in CHO production processes of different IL-2v or IL-2 containing therapeutic proteins.     

External water transport is more important than vascular transport in the extreme atmospheric epiphyte Tillandsia usneoides (Spanish moss)

Most epiphytic bromeliads, especially those in the genus Tillandsia, lack functional roots and rely on the absorption of water and nutrients by large, multicellular trichomes on the epidermal surfaces of leaves and stems. Another important function of these structures is the spread of water over the epidermal surface by capillary action between trichome “wings” and epidermal surface. Although critical for the ultimate absorption by these plants, understanding of this function of trichomes is primarily based on light microscope observations. To better understand this phenomenon, the distribution of water was followed by its attenuation of cold neutrons following application of H₂O to the cut end of Tillandsia usneoides shoots. Experiments confirmed the spread of added water on the external surfaces of this “atmospheric” epiphyte. In a morphologically and physiologically similar plant lacking epidermal trichomes, water added to the cut end of a shoot clearly moved via its internal xylem and not on its epidermis. Thus, in T. usneoides, water moves primarily by capillarity among the overlapping trichomes forming a dense indumentum on shoot surfaces, while internal vascular water movement is less likely. T. usneoides, occupying xeric microhabitats, benefits from reduction of water losses by low‐shoot xylem hydraulic conductivities.     

Efficient Evaluation of Ranking Procedures when the Number of Units is Large,with Application to SNP Identification

Simulation‐based assessment is a popular and frequently necessary approach for evaluating statistical procedures. Sometimes overlooked is the ability to take advantage of underlying mathematical relations and we focus on this aspect. We show how to take advantage of large‐sample theory when conducting a simulation using the analysis of genomic data as a motivating example. The approach uses convergence results to provide an approximation to smaller‐sample results, results that are available only by simulation. We consider evaluating and comparing various ranking‐based methods for identifying the most highly associated SNPs in a genome‐wide association study, derive integral equation representations of the pre‐posterior distribution of percentiles produced by three ranking methods, and provide examples comparing performance. These results are of interest in their own right and set the framework for a more extensive set of comparisons.