Analysis of endophytic bacterial diversity in seeds of different genotypes of cotton and the suppression of Verticillium wilt pathogen infection by a synthetic microbial community.

BACKGROUND: In agricultural production, fungal diseases significantly impact the yield and quality of cotton (Gossypium spp.) with Verticillium wilt posing a particularly severe threat. RESULTS: This study is focused on investigating the effectiveness of endophytic microbial communities present in the seeds of disease-resistant cotton genotypes in the control of cotton Verticillium wilt. The technique of 16S ribosomal RNA (16S rRNA) amplicon sequencing identified a significant enrichment of the Bacillus genus in the resistant genotype Xinluzao 78, which differed from the endophytic bacterial community structure in the susceptible genotype Xinluzao 63. Specific enriched strains were isolated and screened from the seeds of Xinluzao 78 to further explore the biological functions of seed endophytes. A synthetic microbial community (SynCom) was constructed using the broken-rod model, and seeds of the susceptible genotype Xinluzao 63 in this community that had been soaked with the SynCom were found to significantly control the occurrence of Verticillium wilt and regulate the growth of cotton plants. Antibiotic screening techniques were used to preliminarily identify the colonization of strains in the community. These techniques revealed that the strains can colonize plant tissues and occupy ecological niches in cotton tissues through a priority effect, which prevents infection by pathogens. CONCLUSION: This study highlights the key role of seed endophytes in driving plant disease defense and provides a theoretical basis for the future application of SynComs in agriculture.

Habitat effects on reproductive phenotype, pollinator behavior, fecundity, and mating outcomes of a bumble bee-pollinated herb.

PREMISE: Fecundity and mating outcomes commonly differ among plant populations occupying contrasting environments. If self-pollination occurs primarily among flowers within plants, contrasting reproductive outcomes among populations must reflect environmental effects on plant-pollinator interactions. Specifically, local conditions could affect features of plant phenotypes that influence pollinator behavior, in turn modifying plant reproductive outcomes. METHODS: We compared phenotypes, pollinator abundance and behavior, and female fecundity and mating in two meadow populations and two forest populations of Aconitum kusnezoffii within 3 km of each other. Mating outcomes were assessed using microsatellites. RESULTS: Meadow plants generally produced more, shorter ramets with more, larger flowers, but less nectar per flower than forest plants. These differences likely largely represent phenotypic plasticity. Individual bumble bees visited more flowers on forest plants, likely because the more abundant bees in the meadows depleted nectar availability, as indicated by briefer visits to individual flowers. Despite similar fruit set in both habitats, forest plants set more seeds per fruit. Nevertheless, meadow plants produced more seeds overall, owing to sevenfold greater flower production. Consistent with individual bees visiting fewer flowers on meadow plants, more of their seeds were outcrossed. However, the outcrossed seeds of forest plants included more male mates. CONCLUSIONS: Reproductive outcomes can vary among populations of animal-pollinated plants as a result of differences in the availability of effective pollinators and environmental effects on plant phenotypes, and their functional consequences for pollinator behavior that governs pollen dispersal.

The nature of interspecific interactions and co-diversification patterns, as illustrated by the fig microcosm.

Interactions between mutualists, competitors, and antagonists have contrasting ecological effects that, sustained over generations, can influence micro- and macroevolution. Dissimilar benefits and costs for these interactions should cause contrasting co-diversification patterns between interacting clades, with prevalent co-speciation by mutualists, association loss by competitors, and host switching by antagonists. We assessed these expectations for a local assemblage of 26 fig species (Moraceae: Ficus), 26 species of mutualistic (pollinating), and 33 species of parasitic (galling) wasps (Chalcidoidea). Using newly acquired gene sequences, we inferred the phylogenies for all three clades. We then compared the three possible pairs of phylogenies to assess phylogenetic congruence and the relative frequencies of co-speciation, association duplication, switching, and loss. The paired phylogenies of pollinators with their mutualists and competitors were significantly congruent, unlike that of figs and their parasites. The distributions of macroevolutionary events largely agreed with expectations for mutualists and antagonists. By contrast, that for competitors involved relatively frequent association switching, as expected, but also unexpectedly frequent co-speciation. The latter result likely reflects the heterogeneous nature of competition among fig wasps. These results illustrate the influence of different interspecific interactions on co-diversification, while also revealing its dependence on specific characteristics of those interactions.

Hydraulics play an important role in causing low growth rate and dieback of aging Pinus sylvestris var. mongolica trees in plantations of Northeast China.

The frequently observed forest decline in water-limited regions may be associated with impaired tree hydraulics, but the precise physiological mechanisms remain poorly understood. We compared hydraulic architecture of Mongolian pine (Pinus sylvestris var. mongolica) trees of different size classes from a plantation and a natural forest site to test whether greater hydraulic limitation with increasing size plays an important role in tree decline observed in the more water-limited plantation site. We found that trees from plantations overall showed significantly lower stem hydraulic efficiency. More importantly, plantation-grown trees showed significant declines in stem hydraulic conductivity and hydraulic safety margins as well as syndromes of stronger drought stress with increasing size, whereas no such trends were observed at the natural forest site. Most notably, the leaf to sapwood area ratio (LA/SA) showed a strong linear decline with increasing tree size at the plantation site. Although compensatory adjustments in LA/SA may mitigate the effect of increased water stress in larger trees, they may result in greater risk of carbon imbalance, eventually limiting tree growth at the plantation site. Our results provide a potential mechanistic explanation for the widespread decline of Mongolian pine trees in plantations of Northern China.

Elevated ozone concentration decreases whole-plant hydraulic conductance and disturbs water use regulation in soybean plants.

Elevated tropospheric ozone (O3 ) concentration has been shown to affect many aspects of plant performance including detrimental effects on leaf photosynthesis and plant growth. However, it is not known whether such changes are accompanied by concomitant responses in plant hydraulic architecture and water relations, which would have great implications for plant growth and survival in face of unfavorable water conditions. A soybean (Glycine max (L.) Merr.) cultivar commonly used in Northeast China was exposed to non-filtered air (NF, averaged 24.0 nl l-1 ) and elevated O3 concentrations (eO3 , 40 nl l-1 supplied with NF air) in six open-top chambers for 50 days. The eO3 treatment resulted in a significant decrease in whole-plant hydraulic conductance that is mainly attributable to the reduced hydraulic conductance of the root system and the leaflets, while stem and leaf petiole hydraulic conductance showed no significant response to eO3 . Stomatal conductance of plants grown under eO3 was lower during mid-morning but significantly higher at midday, which resulted in substantially more negative daily minimum water potentials. Moreover, excised leaves from the eO3 treated plants showed significantly higher rates of water loss, suggesting a lower ability to withhold water when water supply is impeded. Our results indicate that, besides the direct detrimental effects of eO3 on photosynthetic carbon assimilation, its influences on hydraulic architecture and water relations may also negatively affect O3 -sensitive crops by deteriorating the detrimental effects of unfavorable water conditions.

[Diagnostic value of selective small bowel enteroclysis in imageology of intestinal obstruction: clinical analysis of 98 cases].

OBJECTIVE: To improve the diagnosticability of selective enteroclysis in the area of intestinal obstruction, by reviewing the cases of selective intestinal enteroclysis through a naso-intestinal decompression tube, and evaluating its diagnostic concordance level and the influence factors. METHODS: The selective enteroclysis was different from traditional enteroclysis; it utilized a naso-intestinal decompression long tube to perform local intestinal opacification. In the four years between Apr. 2008 and Apr. 2012, 98 cases of selective intestinal enteroclysis were analyzed retrospectively, and diagnostic concordance value was made between the radiologic diagnosis and the final clinical diagnosis recorded in the medical history according to an evaluating criterion. Five scores were used in the evaluating system: 0 meant that the enteroclysis had no valuable information to provide; 0.25 meant that the enteroclysis could prompt the occurring of obstruction, but could not provide the information of location and cause; 0.50 meant that the enteroclysis could find the location of obstruction, but could not determine the cause; 0.75 meant that the enteroclysis could provide some valuable analysis of the causes of the obstruction, and very close to the final clinical diagnosis; 1.00 meant that the complete concordance between the enteroclysis diagnosis and the final clinical diagnosis. The influence factors would also be considered to improve the competence of the selective enteroclysis in the diagnosis of intestinal obstruction. RESULTS: In the 98 cases, 53.1% had definite abdominal operative history. The most common cause of obstruction was conglutination between intestinal loops when discharged from hospital, almost occupying 50%. In this group of cases, the most common types were ileum obstruction (47.6%), multiple location obstruction (41.7%) and incomplete obstruction (59.5%). Conglutination and stricture of the intestinal was the common radiologic appearance (61.9%). There were 50 cases with higher concordance scoring 0.75 or 1.00, in comparison, there were 25 cases with lower concordance scoring 0 or 0.25. The difference between the two groups had statistical significance. CONCLUSION: As a combination of traditional enteroclysis and naso-intestinal decompression tube, selective intestinal enteroclysis could exert higher diagnostic ability than that of traditional enteroclysis and also could break through the limitations of traditional enteroclysis in the condition of intestinal obstruction. This method has higher diagnostic concordance and could provide valuable information in obstruction location, extent, severity and possible causes. The main factor influencing the effectiveness of the examination is the location of the decompression tube and dynamic observation would be very helpful and important.

Is hemiepiphytism an adaptation to high irradiance? Testing seedling responses to light levels and drought in hemiepiphytic and non-hemiepiphytic Ficus.

The epiphytic growth habit in many Ficus species during their juvenile stages has commonly been hypothesized to be an adaptation for avoiding deep shade in the forest understory, but this has never been tested experimentally. We examined growth and ecophysiology in seedlings of three hemiepiphytic (Hs) and three non-hemiepiphytic (NHs) Ficus species grown under different irradiance levels. Both Hs and NHs exhibited characteristics of high light requiring species, such as high plasticity to growth irradiance and relatively high maximum photosynthetic assimilation rates. Diurnal measurements of leaf gas exchange showed that Hs have much shorter active photosynthetic periods than NHs; moreover, leaves of Hs have lower xylem hydraulic conductivity but stronger drought tolerance as indicated by much lower rates of leaf diebacks during the drought treatment. Seedlings of NHs had 3.3- and 13.3-fold greater height and biomass than those of Hs species after growing in the nursery for 5 months, indicating a trade-off between growth and drought tolerance due to the conflicting requirements for xylem conductivity and cavitation resistance. This study does not support the shade-avoidance hypothesis; rather, it suggests that the canopy regeneration in Hs is an adaptation to avoid alternative terrestrial growth-related risks imposed to tiny Ficus seedlings. The NHs with terrestrial regeneration reduce these risks by having an initial burst of growth to rapidly gain relatively large seedling sizes, while in Hs seedlings more conservative water use and greater drought tolerance for surviving the canopy environment are intrinsically associated with slow growth.

Host insect specificity and interspecific competition drive parasitoid diversification in a plant-insect community.

Ecological interactions among plants, insect herbivores, and parasitoids are pervasive in nature and play important roles in community assembling, but the codiversification of tri-trophic interactions has received less attention. Here we compare pairwise codiversification patterns between a set of 22 fig species, their herbivorous pollinating and galling wasps, and their parasitoids. The parasitoid phylogeny showed significant congruence and more cospeciation events with host insects phylogeny than with host plants. These results suggest that parasitoid phylogeny and speciation is more closely related to their host insects than to their host plants. The pollinating wasps hosted more parasitoid species than gallers and indicated a more intense interspecific competition among parasitoids associated with pollinators. Closer matching and fewer evolutionary host shifts were found between parasitoids and galler hosts than between parasitoids and pollinator hosts. These results suggest that interspecific competition among parasitoids, rather than resource availability of host wasps, is the main driver of the codiversification pattern in this community. Therefore, our study highlights the important role of interspecific competition among high trophic level insects in plant-insect tri-trophic community assembling.

Stem hydraulic traits and leaf water-stress tolerance are co-ordinated with the leaf phenology of angiosperm trees in an Asian tropical dry karst forest.

BACKGROUND AND AIMS: The co-occurring of evergreen and deciduous angiosperm trees in Asian tropical dry forests on karst substrates suggests the existence of different water-use strategies among species. In this study it is hypothesized that the co-occurring evergreen and deciduous trees differ in stem hydraulic traits and leaf water relationships, and there will be correlated evolution in drought tolerance between leaves and stems. METHODS: A comparison was made of stem hydraulic conductivity, vulnerability curves, wood anatomy, leaf life span, leaf pressure-volume characteristics and photosynthetic capacity of six evergreen and six deciduous tree species co-occurring in a tropical dry karst forest in south-west China. The correlated evolution of leaf and stem traits was examined using both traditional and phylogenetic independent contrasts correlations. KEY RESULTS: It was found that the deciduous trees had higher stem hydraulic efficiency, greater hydraulically weighted vessel diameter (D(h)) and higher mass-based photosynthetic rate (A(m)); while the evergreen species had greater xylem-cavitation resistance, lower leaf turgor-loss point water potential (π(0)) and higher bulk modulus of elasticity. There were evolutionary correlations between leaf life span and stem hydraulic efficiency, A(m), and dry season π(0). Xylem-cavitation resistance was evolutionarily correlated with stem hydraulic efficiency, D(h), as well as dry season π(0). Both wood density and leaf density were closely correlated with leaf water-stress tolerance and A(m). CONCLUSIONS: The results reveal the clear distinctions in stem hydraulic traits and leaf water-stress tolerance between the co-occurring evergreen and deciduous angiosperm trees in an Asian dry karst forest. A novel pattern was demonstrated linking leaf longevity with stem hydraulic efficiency and leaf water-stress tolerance. The results show the correlated evolution in drought tolerance between stems and leaves.

[Expression of Bcl-w protein in human small intestinal adenocarcinoma and effect of Bcl-w siRNA on apoptosis in intestinal adenocarcinoma HuTu-80 cells].

OBJECTIVE: To investigate the expression of apoptosis-related protein Bcl-w in adenocarcinoma of the small intestine, and the apoptotic effect of Bcl-w siRNA on small intestinal adenocarcinoma cells HuTu-80. METHODS: Forty-two tissue samples were examined in our study, including 7 cases from human small intestinal adenocarcinoma, and 35 cases from normal small intestine served as control. The expression of Bcl-w was detected by immunohistochemistry (IHC). Western blot analysis was performed to confirm whether Bcl-w siRNA could effectively down-regulate Bcl-w protein after HuTu-80 cells were transfected with Bcl-w siRNA. The cells were treated with chemotherapeutic agent 5-Fu to observe whether Bcl-w protein-silecing affects the pro-apoptotic effect of 5-Fu. Flow cytometry analysis was used for assessment of apoptotic rate of HuTu-80 cells cultured with Bcl-w siRNA alone, with 5-Fu alone, and with combination of Bcl-w siRNA and 5-Fu, using untreated HuTu-80 cells as control. RESULTS: The positive rate of Bcl-w expression was significantly higher in small intestinal adenocarcinoma than that in normal tissue (85.7% vs. 25.7%, P=0.005). Compared with the control group, Bcl-w siRNA transfection effectively down-regulated the expression of Bcl-w protein (P<0.05). The apoptosis in HuTu-80 cells was not increased significantly in Bcl-w-/-cells compared with that of control group (12.4±2.2)% vs. (8.6±1.7)% (P>0.05). However, compared with the 5-Fu group, the apoptosis in HuTu-80 cells was effectively enhanced after combination treatment with Bcl-w siRNA and 5-Fu (45.7±2.1)% vs. (71.6±3.2)% (P<0.05). CONCLUSIONS: Bcl-w protein plays a significant role in the carcinogenesis of human small intestinal adenocarcinoma. Down-regulation of Bcl-w protein in small intestine adenocarcinoma HuTu-80 cells leads them susceptible to 5-Fu.

High-throughput sequencing reveals soil bacterial community structure and their interactions with environmental factors of the grassland fairy ring.

Fairy rings (FRs) are common ecological grassland landscapes that have been studied for a long time. However, little is known about their interactions with soil physicochemical properties and bacterial communities. This study performed high-throughput sequencing of the 16S rRNA V3-V4 variable regions of soil bacteria in the three concentric zones of chosen FR, namely, the ON zone, on the ring; IN zone, inside the ring; and OUT zone, outside the ring. Also, the change in physicochemical properties and enzyme activities of the soil were determined. This study found that the nutrients and enzyme activities on the ring were higher than inside and outside of the ring. The activities of microorganisms were frequent and the plant grew splendidly. The bacterial species diversity was the lowest on the ring with the main genera Pseudonocardia, Streptosporangium, Kribbella and Promicromonospora. The imbalance of the microbial community structure at different ring zones may be the driving factor for the continuous outward expansion of FRs. Soil available phosphorus, electrical conductivity, total nitrogen and organic matter positively correlated with the distribution of FR soil bacteria.

[Hydraulics and non-structural carbohydrate contents of Ginkgo biloba under different environmental conditions in Shenyang City, China.] / 沈阳市区不同环境下银杏水力特征和非结构性碳水化合物含量.

Ginkgo biloba is an important urban ornamental tree species, but poor growth and damages often occur in urban environments. As a street tree species, the decline and death of G. biloba is particularly frequent, with the relevant physiological mechanism being unclear. In this study, we compared hydraulic characteristics, non-structural carbohydrate (NSC) contents and health status between G. biloba trees growing along the streets and those in parks in Shenyang City. The results showed that G. biloba growing along the streets showed higher degrees of branch and leaf mortality than those growing in the parks. Branches of G. biloba growing in both conditions showed lower degrees of xylem embolism. Branch hydraulic vulnerable curves of G. biloba under the two growing conditions also showed no significant difference, with the average P50 being lower than -2.8 MPa. G. biloba growing along the streets had lower leaf area specific conductivity, smaller tracheid diameter, smaller hydraulic diameter, lower soluble sugar content and total NSC than those growing in parks. Hydraulic failure was not the direct reason for the decline and mortality of G. biloba growing along streets. Under the more stressed growth conditions along the streets, G. biloba had smaller tracheid diameters in stems and lower Huber values, which limited the ability of water transport and photosynthetic carbon assimilation at the whole branch level. In addition, in order to deal with more serious stress such as greater heat and drought stresses, G. biloba might need to invest more NSC to repair damage, which further decreaded NSC contents in branches and increased the risk of carbon imbalance. At the same habitat (street or park), xylem hydraulics and NSC contents of G. biloba also showed relatively large difference among sampling sites, which reflected large heterogeneity of urban environment for tree growth.

Ecology of hemiepiphytism in fig species is based on evolutionary correlation of hydraulics and carbon economy.

Woody hemiepiphytic species (Hs) are important components of tropical rain forests, and they have been hypothesized to differ from non-hemiepiphytic tree species (NHs) in adaptations relating to water relations and carbon economy; but few studies have been conducted comparing ecophysiological traits between the two growth forms especially in an evolutionary context. Using common-garden plants of the genus Ficus, functional traits related to plant hydraulics and carbon economy were compared for seven NHs and seven Hs in their adult terrestrial "tree-like" growth phase. We used phylogenetically independent contrasts to test the hypothesis that differences in water availability selected for contrasting suites of traits in Hs and NHs, driving evolutionary correlations among functional traits including hydraulic conductivity and photosynthetic traits. Species of the two growth forms differed in functional traits; Hs had substantially lower xylem hydraulic conductivity and stomatal conductance, and higher instantaneous photosynthetic water use efficiency. Leaf morphological and structural traits also differed strikingly between the two growth forms. The Hs had significantly smaller leaves, higher leaf mass per area (LMA), and smaller xylem vessel lumen diameters. Across all the species, hydraulic conductivity was positively correlated with leaf gas exchange indicating high degrees of hydraulic-photosynthetic coordination. More importantly, these correlations were supported by correlations implemented on phylogenetic independent contrasts, suggesting that most trait correlations arose through repeated convergent evolution rather than as a result of chance events in the deep nodes of the lineage. Vatiation in xylem hydraulic conductivity was also centrally associated with a suite of other functional traits related to carbon economy and growth, such as LMA, water use efficiency, leaf nutrient concentration, and photosynthetic nutrient use efficiency, indicating important physiological constraints or trade-offs among functional traits. Shifts in this trait cluster apparently related to the adaptation to drought-prone canopy growth during the early life cycle of Hs and clearly affected ecophysiology of the later terrestrial stage of these species. Evolutionary flexibility in hydraulics and associated traits might be one basis for the hyper-diversification of Ficus species in tropical rain forests.

Genome-Wide Characterization and Expression Analysis Provide Basis to the Biological Function of Cotton FBA Genes.

Fructose-1,6-biphosphate aldolase (FBA) is a multifunctional enzyme in plants, which participates in the process of Calvin-Benson cycle, glycolysis and gluconeogenesis. Despite the importance of FBA genes in regulating plant growth, development and abiotic stress responses, little is known about their roles in cotton. In the present study, we performed a genome-wide identification and characterization of FBAs in Gossypium hirsutum. Totally seventeen GhFBA genes were identified. According to the analysis of functional domain, phylogenetic relationship, and gene structure, GhFBA genes were classified into two subgroups. Furthermore, nine GhFBAs were predicted to be in chloroplast and eight were located in cytoplasm. Moreover, the promoter prediction showed a variety of abiotic stresses and phytohormone related cis-acting elements exist in the 2k up-stream region of GhFBA. And the evolutionary characteristics of cotton FBA genes were clearly presented by synteny analysis. Moreover, the results of transcriptome and qRT-PCR analysis showed that the expression of GhFBAs were related to the tissue distribution, and further analysis suggested that GhFBAs could respond to various abiotic stress and phytohormonal treatments. Overall, our systematic analysis of GhFBA genes would not only provide a basis for the understanding of the evolution of GhFBAs, but also found a foundation for the further function analysis of GhFBAs to improve cotton yield and environmental adaptability.

karmoisin and cardinal ortholog genes participate in the ommochrome synthesis of Nilaparvata lugens (Hemiptera: Delphacidae).

Ommochrome is the major source for eye coloration of all insect species so far examined. Phenoxazinone synthetase (PHS) has always been regarded as the terminal step enzyme for ommochrome formation, which is encoded by cardinal or karmoisin genes. Our previous study indicated that the karmoisin ortholog gene (Nl-karmoisin) product in the brown planthopper (BPH) was a monocarboxylate transporter, while not a PHS. Here, based on full-length complementary DNA, the cardinal ortholog gene in BPH (Nl-cardinal) product was predicted to be a haem peroxidase rather than a PHS. We suggest for the first time that neither karmoisin nor cardinal encodes the PHS, but whether PHS participates in BPH eye pigmentation needs further research. Nymphal RNA interference (RNAi) experiments showed that knockdown Nl-cardinal transcript led the BPH ocelli and compound eye to color change from brown to red, while knockdown Nl-karmoisin only made the ocelli present the red phenotype. Notably, not only the Nl-cardinal transcript, dscd injection (Nl-cardinal targeting double-stranded DNA (dsRNA)) also significantly reduced the Nl-karmoisin transcript by 33.7%, while dska (Nl-karmoisin targeting dsRNA) injection did not significantly change the Nl-cardinal transcript. Considering the above RNAi and quantitative real-time polymerase chain reaction results, we propose that Nl-cardinal plays a more important role in ommochrome synthesis than Nl-karmoisin, and it may be an upstream gene of Nl-karmoisin. The present study suggested that both karmoisin and cardinal ortholog genes play a role in ommochrome synthesis in a hemimetabolous insect.

The interaction between nonstructural carbohydrate reserves and xylem hydraulics in Korean pine trees across an altitudinal gradient.

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.

Microenvironment in the canopy rivals the host tree water status in controlling sap flow of a mistletoe species.

Mistletoes absorb water from the vascular system of their hosts and thus the water use of mistletoes can be influenced by the water status of their hosts besides abiotic environmental conditions; however, there is a lack of studies on the dynamics of mistletoe water utilization in relation to both types of controlling factors. By building a canopy platform at 20 m above the ground, we monitored the dynamic changes of sap flow of Viscum coloratum (Kom.) Nakai (Loranthaceae) in combination with continuous measurements of microclimatic variables and volumetric water content (VWC) of its host tree branch xylem. We found that the host tree VWC exhibited substantial fluctuations during sunny days but lower VWC of the host did not negatively affect the sap flow of V. coloratum. Hourly and daily mean transpiration rates (Esap) of V. coloratum calculated from sap flow measurements showed strong positive correlations with photosynthetic photon flux density (PPFD) and vapor pressure deficit (VPD) measured in close vicinity to the point of mistletoe attachment. The mean Esap of V. coloratum was substantially higher than that of their host during clear days (4.55 ± 0.54 vs 2.01 ± 0.15 kg m-2 day-1). Moreover, the mistletoe-to-host transpiration ratio was not constant but became increasingly larger with the increase of PPFD or VPD on both hourly and daily bases, suggesting a weaker control of water loss in the mistletoe in comparison to its host species. The strong dependence of mistletoe Esap on micrometeorological variables and its decoupling from the host tree xylem water status suggests that the development of dense tree canopy functions as a potential mechanism for the host trees in reducing the competitive water use of mistletoes. These findings have important implications for the interactions between mistletoe species and their host trees in temperate forests.

Responses of hydraulics at the whole-plant level to simulated nitrogen deposition of different levels in Fraxinus mandshurica.

Nitrogen (N) deposition is expected to have great impact on forest ecosystems by affecting many aspects of plant-environmental interactions, one of which involves its influences on plant water relations through modifications of plant hydraulic architecture. However, there is a surprising lack of integrative study on tree hydraulic architecture responses to N deposition, especially at the whole-plant level. In the present study, we used a 5-year N addition experiment to simulate the effects of six different levels of N deposition (20-120 kg ha(-1) year(-1)) on growth and whole-plant hydraulic conductance of a dominant tree species (Fraxinus mandshurica Rupr.) from the typical temperate forest of NE China. The results showed that alleviation of N limitation by moderate concentrations of fertilization (20-80 kg ha(-1) year(-1)) promoted plant growth, but further N additions on top of the threshold level showed negative effects on plant growth. Growth responses of F. mandshurica seedlings to N addition of different concentrations were accompanied by corresponding changes in whole-plant hydraulic conductance; higher growth rate was accompanied by reduced whole-plant hydraulic conductance (Kplant) and higher leaf water-use efficiency. A detailed analysis on hydraulic conductance of different components of the whole-plant water transport pathway revealed that changes in root and leaf hydraulic conductance, rather than that of the stem, were responsible for Kplant responses to N fertilization. Both plant growth and hydraulic architecture responses to increasing levels of N addition were not linear, i.e., the correlation between measured parameters and N availability exhibited bell-shaped curves with peak values observed at medium levels of N fertilization. Changes in hydraulic architecture in response to fertilization found in the present study may represent an important underlying mechanism for the commonly observed changes in water-related tree performances in response to N deposition.

Mir-126 inhibits growth of SGC-7901 cells by synergistically targeting the oncogenes PI3KR2 and Crk, and the tumor suppressor PLK2.

MicroRNA (miRNA)-126 (miR-126) was reported to be downregulated and to act as a tumor suppressor in cancers of the lung, cervix, bladder and prostate. However, the functions of miR-126 in gastric cancer appear to be diverse and are largely unknown. MiR-126 was reported to act as a tumor suppressor by targeting the Crk gene, or as an oncogene by targeting the SOX2 gene in gastric cancer. We identified that the expression of miR-126 was decreased in gastric cancer cell lines and tissues. PLK2, a tumor suppressor gene, was directly regulated by miR-126 in SGC-7901 cells. Overexpression of miR-126 not only suppressed the growth and clone formation of SGC-7901 cells, but also induced apoptosis in vitro, whereas inhibition of miR-126 slightly promoted SGC-7901 cell proliferation. The cell cycle was not affected by miR-126. Moreover, miR-126 suppressed tumor growth in vivo in a xenograft model. PLK2, PI3KR2 and Crk were regulated by miR-126 in SGC-7901 cells. We infer that the functions of miR-126 in gastric cancer depend on synergistic targeting balance between oncogenes and anti-oncogenes. Our study indicates that miR-126 is a tumor suppressor, which in the future may become a therapeutic target for gastric cancer.