Environmental filtering rather than dispersal limitation dominated plant community assembly in the Zoige Plateau

Identifying the mechanisms that underlie the assembly of plant communities is critical to the conservation of terrestrial biodiversity. However, it is seldom measured or quantified how much deterministic versus stochastic processes contribute to community assembly in alpine meadows. Here, we measured the decay in community similarity with spatial and environmental distance in the Zoige Plateau. Furthermore, we used redundancy analysis (RDA) to divide the variations in the relative abundance of plant families into four components to assess the effects of environmental and spatial. Species assemblage similarity liner declined with geographical distance (p < .001, R ² = .6388), and it decreased significantly with increasing distance of total phosphorus (TP), alkali‐hydrolyzable nitrogen (AN), available potassium (AK), nitrate nitrogen (NO₃ ⁺–N), and ammonia nitrogen (NH₄ ⁺–N). Environmental and spatial variables jointly explained a large proportion (55.2%) of the variation in the relative abundance of plant families. Environmental variables accounted for 13.1% of the total variation, whereas spatial variables accounted for 11.4%, perhaps due to the pronounced abiotic gradients in the alpine areas. Our study highlights the mechanism of plant community assembly in the alpine ecosystem, where environmental filtering plays a more important role than dispersal limitation. In addition, a reasonably controlled abundance of Compositae (the family with the highest niche breadth and large niche overlap value with Gramineae and Cyperaceae) was expected to maintain sustainable development in pastoral production. These results suggest that management measures should be developed with the goal of improving or maintaining suitable local environmental conditions.     

Development of mechanistically based model for simulating soluble microbial products generation in an aerated/non-aerated SBR

Soluble microbial products (SMPs) are considered as the main organic components in wastewater treatment plant effluent from biological wastewater treatment systems. To investigate and explore SMP metabolism pathway for further treatment and control, two innovative mechanistically based activated sludge models were developed by extension of activated sludge model no.3 (ASM3). One was the model by combining SMP formation and degradation (ASM3-SMP model) processes with ASM3, and the other by combining both SMP and simultaneous substrate storage and growth (SSSG) mechanisms with ASM3 (SSSG-ASM3-SMP model). The detailed schematic modification and process supplements were introduced for comprehensively understanding all the mechanisms involved in the activated sludge process. The evaluations of these two models were demonstrated by a laboratory-scale sequencing batch reactor (SBR) operated under aerated/non-aerated conditions. The simulated and measured results indicated that SMP comprised about 83% of total soluble chemical oxygen demand (SCOD) in which biomass-associated products (BAPs) were predominant compared with utilization-associated products (UAPs). It also elucidated that there should be a minimum SMP value as the reactive time increases continuously and this conclusion could be used to optimize effluent SCOD in activated sludge processes. The comparative results among ASM3, ASM3-SMP and SSSG-ASM3-SMP models and the experimental measurements (SCOD, ammonia and nitrate nitrogen) showed clearly the best agreement with SSSG-ASM3-SMP simulation values (R = 0.993), strongly suggesting that both SMP formation and degradation and SSSG mechanisms are necessary in biologically activated sludge modeling for municipal wastewater treatment.     

DNA methylation changes in photoperiod-thermo-sensitive male sterile rice PA64S under two different conditions

Epigenetic modification can occur at a high frequency in crop plants and might generate phenotypic variation without changes in DNA sequences. DNA methylation is an important epigenetic modification that may contribute to environmentally-induced phenotypic variations by regulating gene expression. Rice Photoperiod-Thermo-Sensitive Genic Male Sterile (PTGMS) lines can transform from sterility to fertility under lower temperatures and short-day (SD) conditions during anther development. So far, little is known about the DNA methylation variation of PTGMS throughout the genome in rice. In this study, we investigated DNA cytosine methylation alterations in the young panicles of PTGMS line PA64S under two different conditions using methylation sensitive amplified polymorphism (MSAP) method. Compared with the DNA methylation level of PA64S under lower temperatures and SD conditions (fertility), higher methylation was observed in PA64S (sterility). The sequences of 25 differentially amplified fragments were successfully obtained and annotated. Three methylated fragments, which are homologous to D2, NAD7 and psaA, were confirmed by bisulfite sequencing and their expression levels were also evaluated by qPCR. Real time quantitative PCR analysis revealed that five of the six selected methylated genes were downregulated in PA64S (sterility). These results suggested that DNA methylation may be involved in the sterility–fertility transition of PA64S under two different environmental conditions.     

Cyanidin-3-glucoside, a natural product derived from blackberry, exhibits chemopreventive and chemotherapeutic activity

Epidemiological data suggest that consumption of fruits and vegetables has been associated with a lower incidence of cancer. Cyanidin-3-glucoside (C3G), a compound found in blackberry and other food products, was shown to possess chemopreventive and chemotherapeutic activity in the present study. In cultured JB6 cells, C3G was able to scavenge ultraviolet B-induced *OH and O2-* radicals. In vivo studies indicated that C3G treatment decreased the number of non-malignant and malignant skin tumors per mouse induced by 12-O-tetradecanolyphorbol-13-acetate (TPA) in 7,12-dimethylbenz[a]anthracene-initiated mouse skin. Pretreatment of JB6 cells with C3G inhibited UVB- and TPA-induced transactivation of NF-kappaB and AP-1 and expression of cyclooxygenase-2 and tumor necrosis factor-alpha. These inhibitory effects appear to be mediated through the inhibition of MAPK activity. C3G also blocked TPA-induced neoplastic transformation in JB6 cells. In addition, C3G inhibited proliferation of a human lung carcinoma cell line, A549. Animal studies showed that C3G reduced the size of A549 tumor xenograft growth and significantly inhibited metastasis in nude mice. Mechanistic studies indicated that C3G inhibited migration and invasion of A549 tumor cells. These finding demonstrate for the first time that a purified compound of anthocyanin inhibits tumor promoter-induced carcinogenesis and tumor metastasis in vivo.     

A combined approach for improving alkaline acetyl xylan esterase production in Pichia pastoris, and effects of glycosylation on enzyme secretion, activity and stability

High level expression of axe1, a gene previously cloned from Volvariella volvacea that encodes an acetyl xylan esterase with two potential N-linked glycosylation sites, has been achieved in Pichia pastoris using a codon-optimized axe1 synthesized by the primer extension PCR procedure. The GC content of the codon-optimized axe1 was 48.62% compared with 55.49% in the native gene. Using the codon-optimized construct, AXE1 expression in P. pastoris was increased from an undetectable level to 136.45U/ml six days after induction of yeast cultures grown in BMMY medium. A further increase (to 463U/ml) was achieved when conditions for yeast culture were optimized as follows: 2.8% methanol, 0.63% casamino acids, and pH 8.0. This latter value represented a 3.4-fold and 246-fold increase in the enzyme levels recorded in non-optimized P. pastoris cultures and in rice straw-grown cultures of V. volvacea, respectively. N-linked glycosylation played an essential role in AXE1 secretion but had only a slight effect on the catalytic activity and stability of the recombinant enzyme.     

KfoE encodes a fructosyltransferase involved in capsular polysaccharide biosynthesis in Escherichia coli K4

Escherichia coli K4 synthesizes a capsular polysaccharide (CPS) consisting of a fructose-branched chondroitin (GalNAc-GlcA(fructose)n), which is a biosynthetic precursor of chondroitin sulfate. Here, the role of kfoE in the modification of the chondroitin backbone was investigated using knock-out and recombinant complementation experiments. kfoE disruption and complementation had no significant effect on cell growth. CPS production was increased by 15 % in the knock-out strain, and decreased by 21 % in the knock-out strain complemented with recombinant kfoE. CPS extracted from the knock-out strain was chondroitin, whereas CPS extracted from the complemented strain was a fructose-branched chondroitin. The results demonstrated that the kfoE gene product altered the fructose group at the C3 position of the GlcA residue during production of K4CPS.     

A concentration-dependent mechanism by which serum albumin inactivates replacement lung surfactants.

Endogenous lung surfactant, and lung surfactant replacements used to treat respiratory distress syndrome, can be inactivated during lung edema, most likely by serum proteins. Serum albumin shows a concentration-dependent surface pressure that can exceed the respreading pressure of collapsed monolayers in vitro. Under these conditions, the collapsed surfactant monolayer can not respread to cover the interface, leading to higher minimum surface tensions and alterations in isotherms and morphology. This is an unusual example of a blocked phase transition (collapsed to monolayer form) inhibiting bioactivity. The concentration-dependent surface activity of other common surfactant inhibitors including fibrinogen and lysolipids correlates well with their effectiveness as inhibitors. These results show that respreading pressure may be as important as the minimum surface tension in the design of replacement surfactants for respiratory distress syndrome.     

利诺吡啶对豚鼠耳蜗外毛细胞和Deiters细胞钾电流的抑制

为探讨KCNQ家族钾通道在耳蜗外毛细胞和Deiters细胞的功能性表达,我们观察并记录了KCNQ家族钾通道阻滞剂利诺吡啶对豚鼠耳蜗单离外毛细胞(outer hair cells,OHCs)和Deiters细胞总钾电流的影响。采用酶孵育加机械分离法分离豚鼠耳蜗单个OHCs和Deiters细胞：运用膜片钳技术,在全细胞模式下记录正常细胞外液中8个外毛细胞和5个Deiters细胞的总钾电流,并观察100μmol／L和200μmol／L利诺吡啶对外毛细胞和Deiters细胞总钾电流的影响。结果观察到,在正常细胞外液中的单离外毛细胞,可记录到四乙基二乙胺敏感的外向性钾电流和静息膜电位附近激活的内向性钾电流(the K^ current activated at negative potential,IKa)两种钾电流,而在单离Deiters细胞中只记录到外向整流性钾电流。在细胞外液中,加入100μmol／L利诺吡啶后,OHCs中的四乙基二乙胺敏感的钾电流峰电流成分被抑制,稳态电流幅值减小,且电流的失活时问常数明显延长;在细胞外液中加入100μmol／L和200μmol／L利诺吡啶后,OHCs的内向性钾电流IKa被完全抑制;而细胞外液中利诺吡啶终浓度为200μmol／L时,Deiters细胞的外向整流性钾电流幅值无明显变化。由此我们推测,KCNQ家族钾通道存在于豚鼠耳蜗外毛细胞,其介导的钾电流是四乙基二乙胺敏感的钾电流的组成部分,并构成全部的IKn,其功能是介导细胞内K^ 外流和防止细胞过度去极化;KCNQ家族钾通道不存在于豚鼠耳蜗Dciters细胞。     

MicroRNA-30a sensitizes tumor cells to cis-platinum via suppressing beclin 1-mediated autophagy

Autophagy is activated in cancer cells during chemotherapy and often contributes to tumor chemotherapy resistance. In this study, we characterized the role of microRNA-30a (miR-30a) in the coordination of cancer cell apoptosis and autophagy, which determines the sensitivity of cancer cells to chemotherapy. First, the autophagy activity in cancer cells increased after cis-dichloro-diamine platinum (cis-DDP) or Taxol treatment, as indicated by the enhanced expression of beclin 1, a key regulator of autophagy, and increased number of LC3-positive autophagosomes. Second, miRNA screening using a TaqMan probe-based quantitative RT-PCR assay identified that miR-30a, a miRNA that targets beclin 1, was significantly reduced in tumor cells by cis-DDP treatment. Forced expression of miR-30a significantly reduced beclin 1 and the autophagy activity of tumor cells induced by cis-DDP. Third, the blockade of tumor cell autophagy activity by miR-30a expression or 3-methyladenine significantly increased tumor cell apoptosis induced by cis-DDP treatment. Finally, an in vivo tumor implantation mouse model clearly showed that elevation of miR-30a in implanted tumor cells by administration of the recombinant lentivirus expressing miR-30a strongly enhanced cis-DDP-induced apoptosis of tumor cells. In conclusion, our results demonstrate for the first time that miR-30a can sensitize tumor cells to cis-DDP via reducing beclin 1-mediated autophagy and that increasing miR-30a level in tumor cells represents a novel approach to enhance the efficacy of chemotherapy during cancer treatment.     

Removal of selectable marker gene from fibroblast cells in transgenic cloned cattle by transient expression of Cre recombinase and subsequent effects on recloned embryo development

Introduction of selectable marker genes to transgenic animals could create an inconvenience to further research and may exaggerate public concerns regarding biological safety. The objective of the current study was to excise loxP flanked neo^R in transgenic cloned cattle by transient expression of Cre recombinase. Green fluorescent protein gene (GFP) was incorporated to monitor Cre expression; therefore, Cre-expressed cells could be selected indirectly by fluorescence-activated cell sorting (FACS). The neo^R was removed and Cre expressed transiently in GFP-positive colonies; excision of neo^R was confirmed by single-blastocyst PCR in recloned blastocysts, with neo^R-free fibroblast cells as donors. There was no difference (P > 0.05) in rates of cleavage (76.0% vs. 68.8%) or blastocyst formation (56.6% vs. 52.9%) between recloned embryos with neo^R-free or neo^R-included donors. The differential staining of recloned blastocysts were similar (P >0.05) in terms of total cell number (124 vs. 122) and the ratio of ICM (Inner Cell Mass) to the total cell number (38.1% vs. 38.2%). Furthermore, pregnancy and calving rates were not different (P > 0.05) from those of the control. In conclusion, we successfully excised neo^R from transgenic cloned cattle; the manipulation did not affect the developmental competence of recloned preimplantation embryos. This approach should benefit bioreactor and transgenic research in livestock.