Responses of species abundance distribution patterns to spatial scaling in subtropical secondary forests

To quantify and assess the processes underlying community assembly and driving tree species abundance distributions(SADs) with spatial scale variation in two typical subtropical secondary forests in Dashanchong state‐owned forest farm, two 1‐ha permanent study plots (100‐m × 100‐m) were established. We selected four diversity indices including species richness, Shannon–Wiener, Simpson and Pielou, and relative importance values to quantify community assembly and biodiversity. Empirical cumulative distribution and species accumulation curves were utilized to describe the SADs of two forests communities trees. Three types of models, including statistic model (lognormal and logseries model), niche model (broken‐stick, niche preemption, and Zipf‐Mandelbrodt model), and neutral theory model, were estimated by the fitted SADs. Simulation effects were tested by Akaike's information criterion (AIC) and Kolmogorov–Smirnov test. Results found that the Fagaceae and Anacardiaceae families were their respective dominance family in the evergreen broad‐leaved and deciduous mixed communities. According to original data and random sampling predictions, the SADs were hump‐shaped for intermediate abundance classes, peaking between 8 and 32 in the evergreen broad‐leaved community, but this maximum increased with size of total sampled area size in the deciduous mixed community. All niche models could only explain SADs patterns at smaller spatial scales. However, both the neutral theory and purely statistical models were suitable for explaining the SADs for secondary forest communities when the sampling plot exceeded 40 m. The results showed the SADs indicated a clear directional trend toward convergence and similar predominating ecological processes in two typical subtropical secondary forests. The neutral process gradually replaced the niche process in importance and become the main mechanism for determining SADs of forest trees as the sampling scale expanded. Thus, we can preliminarily conclude that neutral processes had a major effect on biodiversity patterns in these two subtropical secondary forests but exclude possible contributions of other processes.     

中药组方黄芩汤抑制胃癌细胞增殖的实验研究

目的探讨黄芩汤对胃癌细胞生长增殖及干细胞标志物表达的影响。 方法采用体外优化培养的胃癌细胞株SGC-7901模型,分别加入生理盐水、5-FU、黄岑汤和5-FU+黄芪汤干预,MTT法检测胃癌细胞增殖情况,Real-time PCR检测胃癌干细胞相关表面标志物CD44、EpCAM、CD90的表达情况;并进一步利用胃癌细胞裸鼠荷瘤模型,观察黄岑汤协同5-FU对体内肿瘤生长的抑制效果。细胞增殖曲线多组间数据比较采用重复测量数据方差分析,单时间点多组数据采用单因素方差分析,组间比较采用Tukey法。 结果优化培养的胃癌细胞SGC- 7901呈球形生长,细胞活性染色显示良好的活性状态;MTT结果显示,黄岑汤组（0.44±0.04）能够抑制胃癌细胞的增殖,从第4天起与对照组（0.59±0.02）相比,差异具有统计学意义（F = 39.550,P < 0.01）;黄岑汤联合5-FU组（0.36±0.04）加强5-FU对肿瘤细胞的抑制作用,从第3天起与对照组（0.50±0.01）相比,差异具有统计学意义（F = 10.670,P < 0.01）,与5-FU组（0.42±0.03）对比,差异具有统计学意义（F = 10.670,P < 0.05）;Real-time PCR结果显示黄岑汤联合5-FU可抑制胃癌细胞中肿瘤干细胞相关表面标志物CD44、EpCAM、CD90表达（P < 0.01）;移植瘤生长抑制实验发现黄芪汤组对荷瘤鼠移植瘤的生长具有抑制作用,与对照组相比移植瘤体积减小,差异具有统计学意义（P < 0.01）,黄岑汤联合5-FU组与5-FU组相比对移植瘤抑制效果更明显,差异具有统计学意义（P < 0.01）。 结论黄芪汤能抑制胃癌细胞的生长和增殖,并能协同5-FU产生抗肿瘤作用。     

Climatic variability,hydrologic anomaly,and methane emission can turn productive freshwater marshes into net carbon sources

Freshwater marshes are well‐known for their ecological functions in carbon sequestration, but complete carbon budgets that include both methane (CH₄) and lateral carbon fluxes for these ecosystems are rarely available. To the best of our knowledge, this is the first full carbon balance for a freshwater marsh where vertical gaseous [carbon dioxide (CO₂) and CH₄] and lateral hydrologic fluxes (dissolved and particulate organic carbon) have been simultaneously measured for multiple years (2011–2013). Carbon accumulation in the sediments suggested that the marsh was a long‐term carbon sink and accumulated ~96.9 ± 10.3 (±95% CI) g C m^?2 yr^?1 during the last ~50 years. However, abnormal climate conditions in the last 3 years turned the marsh to a source of carbon (42.7 ± 23.4 g C m^?2 yr^?1). Gross ecosystem production and ecosystem respiration were the two largest fluxes in the annual carbon budget. Yet, these two fluxes compensated each other to a large extent and led to the marsh being a CO₂ sink in 2011 (?78.8 ± 33.6 g C m^?2 yr^?1), near CO₂‐neutral in 2012 (29.7 ± 37.2 g C m^?2 yr^?1), and a CO₂ source in 2013 (92.9 ± 28.0 g C m^?2 yr^?1). The CH₄ emission was consistently high with a three‐year average of 50.8 ± 1.0 g C m^?2 yr^?1. Considerable hydrologic carbon flowed laterally both into and out of the marsh (108.3 ± 5.4 and 86.2 ± 10.5 g C m^?2 yr^?1, respectively). In total, hydrologic carbon fluxes contributed ~23 ± 13 g C m^?2 yr^?1 to the three‐year carbon budget. Our findings highlight the importance of lateral hydrologic inflows/outflows in wetland carbon budgets, especially in those characterized by a flow‐through hydrologic regime. In addition, different carbon fluxes responded unequally to climate variability/anomalies and, thus, the total carbon budgets may vary drastically among years.     

CERNA2: A predictor for clinical progression and poor prognosis in cervical carcinoma

Competing long noncoding RNA 2 (lncRNA 2) for microRNA let-7b (CERNA2) has emerged as an important regulator of tumorigenesis and cancer progression but the clinical value and regulatory function of CERNA2 is yet to be investigated in cervical carcinoma. In our study, we found the CERNA2 expression was obviously increased in cervical carcinoma tissues compared with adjacent normal cervical tissues. In addition, we observed that metastatic lymph nodes exhibited high levels of CERNA2 expression in contrast to primary cervical carcinoma tissues. Furthermore, high CERNA2 expression was associated with advanced clinical stage, lymph node metastasis, distant metastasis poor histological grade, and short overall survival in cervical carcinoma patients. Moreover, high CERNA2 expression acted as an independent unfavorable predictor for overall survival in cervical carcinoma patients. The cell migration and invasion assays in vitro suggested that knockdown of CERNA2 remarkably inhibited cell migration and invasion in cervical carcinoma. In conclusion, CERNA2 functions as an oncogenic lncRNA and may be as a potential therapeutic target in cervical carcinoma.     

Simulating the temporal modulation of inducible DNA damage response in Escherichia coli

Living organisms make great efforts to maintain their genetic information integrity. However, DNA is vulnerable to many chemical or physical agents. To rescue the cell timely and effectively, the DNA damage response system must be well controlled. Recently, single cell experiments showing that after DNA damage, expression of the key DNA damage response regulatory protein oscillates with time. This phenomenon is observed both in eukaryotic and bacterial cells. We establish a model to simulate the DNA damage response (SOS response) in bacterial cell Escherichia coli. The simulation results are compared to the experimental data. Our simulation results suggest that the modulation observed in the experiment is due to the fluctuation of inducing signal, which is coupled with DNA replication. The inducing signal increases when replication is blocked by DNA damage and decreases when replication resumes.     

Genetic engineering of Pseudomonas putida KT2442 for biotransformation of aromatic compounds to chiral cis-diols

Toluene dioxygenase (TDO) catalyzes asymmetric cis-dihydroxylations of aromatic compounds. Pseudomonas putida KT2442 (pSPM01) harboring TDO genes could effectively biotransform a wide-range of aromatic substrates into their cis-diols products. In shake-flask culture, approximately 2.7gl(-1) benzene cis-diols, 8.8gl(-1) toluene cis-diols and 6.0gl(-1) chlorobenzene cis-diols were obtained from the biotransformation process. Furthermore, vgb gene encoding Vitreoscilla hemoglobin protein (VHb) which enhances oxygen microbial utilization rate under low dissolved oxygen concentration was integrated into P. putida KT2442 genome. The oxidation ability of the mutant strain P. putida KTOY02 (pSPM01) harboring TDO gene was increased in the presence of VHb protein. As a result, approximately 3.8, 15.1 or 6.8gl(-1) different cis-diols production was achieved in P. putida KTOY02 (pSPM01) grown in shake-flasks when benzene, toluene or chlorobenzene was used as the substrate. The above results indicate that P. putida KT2442 could be used as a cell factory to biotransform aromatic compounds.     

Microbial transformation of benzene to <Emphasis Type="Italic">cis</Emphasis>-3,5-cyclohexadien-1,2-diols by recombinant bacteria harboring toluene dioxygenase gene <Emphasis Type="Italic">tod</Emphasis>

Toluene dioxygenase (TDO) catalyzes asymmetric cis-dihydroxylation of aromatic compounds. To achieve high efficient biotransformation of benzene to benzene cis-diols, Pseudomonas putida KT2442, Pseudomonas stutzeri 1317, and Aeromonas hydrophila 4AK4 were used as hosts to express TDO gene tod. Plasmid pSPM01, a derivative of broad-host plasmid pBBR1MCS-2 harboring tod from plasmid pKST11, was constructed and introduced into the above three strains. Their abilities to catalyze the biotransformation of benzene to benzene cis-diols, namely, cis-3,5-cyclohexadien-1,2-diols abbreviated as DHCD, were examined. In shake-flask cultivation under optimized culture media and growth condition, benzene cis-diols production by recombinant P. putida KT2442 (pSPM01), P. stutzeri 1317 (pSPM01), and A. hydrophila 4AK4 (pSPM01) were 2.68, 2.13, and 1.17 g/l, respectively. In comparison, Escherichia coli JM109 (pSPM01) and E. coli JM109 (pKST11) produced 0.45 and 0.53 g/l of DHCD, respectively. When biotransformation was run in a 6-l fermenter, DHCD production in P. putida KT2442 (pSPM01) was approximately 60 g/l; this is the highest DHCD production yield reported so far.