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991.
992.
Christine Y. Chang Emmanuelle Fréchette Faride Unda Shawn D. Mansfield Ingo Ensminger 《Plant physiology》2016,172(2):802-818
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 (NPQS), 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. 相似文献
993.
Jiandong Zhang Zhimei Cui Honghong Chang Xiaojun Fan Qiuyong Zhao Wenlong Wei 《Biotechnology letters》2016,38(9):1559-1564
Objectives
To investigate the efficiency of a cofactor regeneration enzyme co-expressed with a glycerol dehydrogenase for the production of 1,3-dihydroxyacetone (DHA).Results
In vitro biotransformation of glycerol was achieved with the cell-free extracts containing recombinant GlyDH (glycerol dehydrogenase from Escherichia coli), LDH (lactate dehydrogenase form Bacillus subtilis) or LpNox1 (NADH oxidase from Lactobacillus pentosus), giving DHA at 1.3 g l?1 (GlyDH/LDH) and 2.2 g l?1 (GlyDH/LpNox1) with total turnover number (TTN) of NAD+ recycling of 6039 and 11100, respectively. Whole cells of E. coli (GlyDH–LpNox1) co-expressing both GlyDH and LpNox1 were constructed and converted 10 g glycerol l?1 to DHA at 0.2–0.5 g l?1 in the presence of zero to 2 mM exogenous NAD+. The cell free extract of E. coli (GlyDH–LpNox) converted glycerol (2–50 g l?1) to DHA from 0.5 to 4.0 g l?1 (8–25 % conversion) without exogenous NAD+.Conclusions
The disadvantage of the expensive consumption of NAD+ for the production of DHA has been overcome.994.
Jingbo Wu Feng Liu Rulin Zhan Guoping Li Yanlong Zhao Chang Jinmei Yanbiao He 《Biotechnology letters》2016,38(5):835-840
Objectives
To develop a sensitive and specific molecular assay for detection of mango malformation disease (MMD), which is caused primarily by Fusarium mangiferae.Results
We screened 100 ISSR primers and identified one (UBC888) that directed the stable amplification of a specific gene fragment of 479 bp (GenBank accession number KJ526382). Based on the DNA sequence of this fragment, a pair of SCAR primers (W342 and W1772) were designed to amplify another gene fragment of 1376 bp (GenBank accession number KJ526383), demonstrating the successful conversion of an ISSR marker to a SCAR marker. An effective and simple detection assay for MMD was established based on this pair of PCR primers, with a high level of specificity and sensitivity to the DNA of F. mangiferae and other species of Fusarium both in vitro and in vivo. It can detect as little as 10 pg fungal DNA from the DNA of mango’s tissues.Conclusions
Our assay provides a practical method for the early diagnosis so that proper prevention of the mango malformation disease can be developed.995.
996.
Relief of hypoxia by angiogenesis promotes neural stem cell differentiation by targeting glycolysis
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Christian Lange Miguel Turrero Garcia Ilaria Decimo Francesco Bifari Guy Eelen Annelies Quaegebeur Ruben Boon Hui Zhao Bram Boeckx Junlei Chang Christine Wu Ferdinand Le Noble Diether Lambrechts Mieke Dewerchin Calvin J Kuo Wieland B Huttner Peter Carmeliet 《The EMBO journal》2016,35(9):924-941
Blood vessels are part of the stem cell niche in the developing cerebral cortex, but their in vivo role in controlling the expansion and differentiation of neural stem cells (NSCs) in development has not been studied. Here, we report that relief of hypoxia in the developing cerebral cortex by ingrowth of blood vessels temporo‐spatially coincided with NSC differentiation. Selective perturbation of brain angiogenesis in vessel‐specific Gpr124 null embryos, which prevented the relief from hypoxia, increased NSC expansion at the expense of differentiation. Conversely, exposure to increased oxygen levels rescued NSC differentiation in Gpr124 null embryos and increased it further in WT embryos, suggesting that niche blood vessels regulate NSC differentiation at least in part by providing oxygen. Consistent herewith, hypoxia‐inducible factor (HIF)‐1α levels controlled the switch of NSC expansion to differentiation. Finally, we provide evidence that high glycolytic activity of NSCs is required to prevent their precocious differentiation in vivo. Thus, blood vessel function is required for efficient NSC differentiation in the developing cerebral cortex by providing oxygen and possibly regulating NSC metabolism. 相似文献
997.
Manuel J. Steinbauer Richard Field John‐Arvid Grytnes Panayiotis Trigas Claudine Ah‐Peng Fabio Attorre H. John B. Birks Paulo A. V. Borges Pedro Cardoso Chang‐Hung Chou Michele De Sanctis Miguel M. de Sequeira Maria C. Duarte Rui B. Elias José María Fernández‐Palacios Rosalina Gabriel Roy E. Gereau Rosemary G. Gillespie Josef Greimler David E. V. Harter Tsurng‐Juhn Huang Severin D. H. Irl Daniel Jeanmonod Anke Jentsch Alistair S. Jump Christoph Kueffer Sandra Nogué Rüdiger Otto Jonathan Price Maria M. Romeiras Dominique Strasberg Tod Stuessy Jens‐Christian Svenning Ole R. Vetaas Carl Beierkuhnlein 《Global Ecology and Biogeography》2016,25(9):1097-1107
998.
999.
1000.
Hongjing Cui Ran Wang Ying Zhou Chang Shu Fengjuan Song Wenying Zhong 《Luminescence》2016,31(3):813-820
To date, several fluorescent probes modified by a single targeting agent have been explored. However, studies on the preparation of dual‐function quantum dot (QD) fluorescent probes with dual‐targeting action and a therapeutic effect are rare. Here, a dual‐targeting CdTe/CdS QD fluorescent probe with a bovine serum albumin–glycyrrhetinic acid conjugate and arginine‐glycine‐aspartic acid was successfully prepared that could induce the apoptosis of liver cancer cells and showed enhanced targeting in in vitro cell imaging. Therefore, the as‐prepared fluorescent probe in this work is an efficient diagnostic tool for the simultaneous detection of liver cancer and breast cancer cells. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献