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Additional file 2: Supplementary Figure 2: Compared with the vector control group, the total protein expression of STAT3 in TetTXNIP group was not change.

Additional file 3: Western blot

Additional file 1: Supplementary Figure 1: The difference between the mRNA expression of TXNIP in calorie-restriced (CR) group (n=2) and calorie-restriced plus insulin treatment (CR+IT) group (n=14) of GDM placenta was analyzed by RT-qPCR (Supplementary Figure 1). The results showed that there was no statistically significant difference in TXNIP mRNA expression between the two groups (p=0.26).

Quantifying inter-specific variations of tree resilience to drought and revealing the underlying mechanisms are of great importance to the understanding of forest functionality, particularly in water-limited regions. So far, comprehensive studies incorporating investigations in inter-specific variations of long-term growth patterns of trees and the underlying physiological mechanisms are very limited. Here, in a semi-arid site of northern China, tree radial growth rate, inter-annual tree-ring growth responses to climate variability, as well as physiological characteristics pertinent to xylem hydraulics, carbon assimilation and drought tolerance were analyzed in seven pine species growing in a common environment. Considerable inter-specific variations in radial growth rate, growth response to drought and physiological characteristics were observed among the studied species. Differently, the studied species exhibited similar degrees of resistance to drought-induced branch xylem embolism, with water potential corresponding to 50% loss hydraulic conductivity ranging from −2.31 to −2.96 MPa. We found that higher branch hydraulic efficiency is related to greater leaf photosynthetic capacity, smaller hydraulic safety margin and lower woody density (P 0.05). Rather, species with higher hydraulic conductivity and photosynthetic capacity were more sensitive to drought stress and tended to show weaker growth resistance to extreme drought events as quantified by tree-ring analyses, which is at least partially due to a trade-off between hydraulic efficiency and safety across species. This study thus demonstrates the importance of drought resilience rather than instantaneous water and carbon flux capacity in determining tree growth in water-limited environments.

Sand-fixing shrub Salix gordejevii plays an important role in sand dune stabilization but often shows severe decline and mortality on the windward slopes of active dunes. The objective of this study was to explore the environmental drivers and physiological mechanisms behind its decline and mortality on the windward slopes of active sand dunes. The xylem hydraulics, sap flow, water relations and non-structural carbohydrate reserves were measured for S. gordejevii plants that respectively inhabited interdune, leeward and windward positions of active dunes with contrasting soil water regimes. Root exposure caused by wind erosion, rather than low soil moisture, predisposed windward S. gordejevii plants to stronger water stress. Correspondingly, the windward plants showed reduced transpirational water use and exhibited a suite of acclimative adjustments in leaf traits favoring water conservation. Despite these adjustments, windward S. gordejevii plants still suffered from higher risks of hydraulic failure and branch mortality. No evidence of carbon depletion in windward S. gordejevii plants was found although the soluble sugar to starch ratios changed significantly. Our findings suggest that wind-erosion-induced root exposure triggers water stress and eventually causes the mortality of windward S. gordejevii plants, during which increased risk of hydraulic dysfunction is pronounced.

Nonstructural carbohydrates (NSC) have been proposed to play an important role in maintaining the hydraulic integrity of trees, particularly in environments with high risks of embolism formation, but knowledge about the interaction between NSC reserves and xylem hydraulics is still very limited. We studied the variation of NSC reserves and hydraulic traits in Pinus koraiensis Sieb. et Zucc. (Korean pine) in March and June across a relatively large altitudinal gradient in Changbai Mountain of Northeast China. One of the major aims was to investigate the potential role NSC plays in maintaining hydraulic integrity of overwintering stems in facing freezing-induced embolism. Consistent with our hypotheses, substantial variations in both NSC contents and hydraulic traits were observed across altitudes and between the two seasons. In March, when relatively high degrees of winter embolism exist, the percentage loss of conductivity (PLC) showed an exponential increase with altitude. Most notably, positive correlations between branch and trunk soluble sugar content and PLC (P = 0.053 and 0.006) were observed across altitudes during this period. These correlations could indicate that more soluble sugars are required for maintaining stem hydraulic integrity over the winter by resisting or refilling freezing-induced embolism in harsher environments, although more work is needed to establish a direct causal relationship between NSC dynamics and xylem hydraulics. If the correlation is indeed directly associated with varying demands for maintaining hydraulic integrity across environmental gradients, greater carbon demands may compromise tree growth under conditions of higher risk of winter embolism leading to a trade-off between competitiveness and stress resistance, which may be at least partially responsible for the lower dominance of Korean pine trees at higher altitudes.

Additional file 3: Text S1. Quality control report of protein extraction, labeling efficiency, and mass spectrometry stability.

Additional file 1: Table S1. Primers sequences designed for RT-qPCR.

Differences in key physiological characteristics between plant species can result in their contrasting performances in vegetation restoration projects, but ecophysiological comparative studies in close relation to ecological restoration projects are scarce. Hedysarum fruticosum Pall. and Caragana microphylla Lam. are two leguminous shrub species widely used in combination for fixation of active sand dunes in semiarid regions of northern China, but they clearly differ in fitness at different stages of dune vegetation development; that is, H. fruticosum quickly gains a community dominance at the initial stage but yields to C. microphylla in a few years after the fixation of dunes. To reveal the underlying mechanism of such a pattern, key physiological characteristics related to xylem water transport, leaf water use, and drought tolerance were compared between these two species at a typical site of sand dune fixation project in Inner Mongolia. Compared with C. microphylla , H. fruticosum shows an acquisitive and risky water management strategy with substantially higher hydraulic efficiency and photosynthetic capability but reduced resistance to drought‐induced xylem embolism, which endows it an advantage under conditions of relatively high soil water availability at the early stage of dune fixation. In contrast, C. microphylla exhibits more conservative water use and characteristics of greater drought tolerance, which results in greater dominance under the more drought‐stressed conditions of the later stage of dune fixation. Our study for the first time provides a potential mechanistic explanation for the clear switching of dominant positions between the two important sand‐fixing shrub species during the sand dune revegetation process. Fil: Guo, Jing‐Jing. Chinese Academy of Sciences; República de China Fil: Gong, Xue-Wei. Chinese Academy of Sciences; República de China Fil: Fang, Li-Dong. Chinese Academy of Sciences; República de China Fil: Jiang, De-Ming. Chinese Academy of Sciences; República de China Fil: Ala, Musa. Chinese Academy of Sciences; República de China Fil: Bucci, Sandra Janet. Universidad Nacional de la Patagonia "San Juan Bosco". Instituto de Biociencias de la Patagonia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biociencias de la Patagonia; Argentina Fil: Scholz, Fabian Gustavo. Universidad Nacional de la Patagonia "San Juan Bosco". Instituto de Biociencias de la Patagonia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biociencias de la Patagonia; Argentina Fil: Goldstein, Guillermo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución. Laboratorio de Ecología Funcional; Argentina. University of Miami; Estados Unidos Fil: Hao, Guang-You. Chinese Academy of Sciences; República de China

Additional file 1.

The increase in nitrogen (N) deposition is expected to have strong influences on forest ecosystems through its direct and indirect effects on tree performance. One way that N deposition can greatly affect tree performance is by altering plant hydraulic architecture and water relations especially in water-limited habitats; however, the magnitude and direction of response are shown to be species and habitat specific and the underlying mechanism requires further investigations. In the present study, we looked at the potential impact of N deposition on stem xylem hydraulics and leaf level water relations of Pinus sylvestris var. mongolica (Mongolian pine), using a five-year N fertilization experiment at a typical plantation site in NE China. Our results showed that N addition significantly enhanced tree growth and altered tree hydraulic architecture in the upper canopy. Hydraulic architecture responses to N addition were mainly attributable to changes in allometric relationship between leaf and stem rather than through its impact on xylem conductive efficiency as indicated by the non-significant differences in stem hydraulic conductivity and decreased leaf area to sapwood area ratio in N-fertilized trees. The N-fertilized Mongolian pine trees exhibited characteristics simulating plants from more water-limited habitats, such as lower leaf osmotic potentials at full turgor and turgor loss, which indicates a less favorable water status related to higher nitrogen availability in a water limited habitat. Moreover, a tendency of reduced leaf lifespan may make the N-fertilized trees more susceptible to carbon imbalance. Our results suggest that, despite tree growth was enhanced in the present experiment, N deposition may negatively affect Mongolian pine plantations through its negative impacts on plant water relations, which may likely deteriorate in more water-limited conditions. Management measures aimed at reducing water use, such as tree thinning, may mitigate the negative influence of N deposition on survival of Mongolian pine trees in water-limited plantations of the vast areas of Northern China.

Populus trees play an important role in windbreak construction in northern China, but widespread decline and mortality of Populus windbreaks have occurred in recent years. The phenomenon of die-backs from the top of Populus trees downwards is commonly found in declining windbreaks preceding tree deaths, particularly in water-limited areas. To provide a mechanistic explanation for such top-down diebacks, we analyzed the variation in xylem hydraulics, leaf water relations, and tissue non-structural carbohydrate contents (NSC) along the vertical axes of Populus pseudo-simonii trees, i.e. one of the most commonly used tree species for creating windbreaks in northern China. Consistent changes were observed along the height gradient of the tree crown, i.e. with the height increase branches showed a clear trend of decrease in hydraulic efficiency and leaves showed symptoms of greater drought stress. The stem hydraulic conductivity standardized using whole cross-sectional wood area decreased from 4.66 at the bottom to 1.69 kg m−1 s−1 MPa−1 at the top of the tree crown. Such a change in hydraulic efficiency was accompanied by significant increase in the degree of xylem embolism (i.e. from

Widespread decline and mortality of shelterbelt forests in water-limited regions of northern China have been occurring over the past few decades and may become more severe under the influence of climate change; however, our understanding on how droughts affect tree performance in a long-term context and the underlying water-related physiological mechanisms are still limited. Here, using a combination of tree-ring analysis and measurement of water-related functional traits, we investigated patterns of long-term radial growth and the underlying physiology in Pinus sylvestris var. mongolica (Mongolian Pine) and Pinus tabuliformis (Chinese Pine) in relation to variation in environmental water availability in Horqin Sandy Land (HSL), i.e. a key area of land desertification control in northern China where the two species are commonly used for afforestation. Particularly, we studied the association between tree-ring growth responses to drought and xylem hydraulics of the two species at the two sites of HSL that differ in climate regimes, examining the potential impacts of climate warming-related aridification on tree performances using a space-for-time substitution approach. Tree-ring analyses revealed greater degrees of recent growth decline, lower resilience to drought, and more severe tree hydraulic limitations in both pine species at the semiarid site compared to the semi-humid site. Tree-ring width indices of both species in the drier site showed significant positive correlations with May-July total precipitation of the current year and negative correlations with mean temperature of the same period, whereas such correlations were not significant at the wetter site. Lower stem hydraulic conductivity and higher degrees of xylem embolism in the drier site suggest that both pine species suffer from stronger hydraulic limitation when the environment gets drier. Moreover, Mongolian pine with a significantly higher hydraulic conductivity consistently showed higher basal area increments than Chinese pine at both sites. Our results suggest that Mongolian pine, the currently most widely used trees to create shelterbelt plantations in desertified areas of northern China, is more susceptible to decline than Chinese pine as the climate becomes hotter and drier, although the former species has a higher growth rate than the latter one. Our investigation provides a mechanistic explanation for the commonly observed decline and dieback of pine trees in water-limited environments of northern China and suggests that Chinese pine may be a better choice to replace Mongolian pine as the main tree species in plantations of the study area with a changed climate regime in the future.