根系在凋落物层中的生长及其对凋落物分解的影响

凋落物分解是生态系统养分循环的重要过程, 直接影响着生态系统功能。植物根系作为重要的生物因子调控着凋落物分解过程, 然而这一重要作用却在凋落物分解的研究中长期被忽视。凋落物中下层养分充足、保水能力强, 为根系生长提供了良好环境; 同时, 生长进入凋落物层的根系通过激发效应、共生真菌、N吸收等方式对分解过程产生了重要影响。该文针对根系生长及其影响因素、根系对凋落物分解的影响及其内在机制等关键方面进行了综述, 并提出了根系生长与凋落物分解之间关系的概念模型, 以期引起大家对这个领域的关注, 并为根系与凋落物分解之间关系的研究提供良好的借鉴。     

Visualization of Subunit Interactions and Ternary Complexes of Protein Phosphatase 2A in Mammalian Cells

Protein phosphatase 2A (PP2A) is a ubiquitous phospho-serine/threonine phosphatase that controls many diverse cellular functions. The predominant form of PP2A is a heterotrimeric holoenzyme consisting of a scaffolding A subunit, a variable regulatory B subunit, and a catalytic C subunit. The C subunit also associates with other interacting partners, such as α4, to form non-canonical PP2A complexes. We report visualization of PP2A complexes in mammalian cells. Bimolecular fluorescence complementation (BiFC) analysis of PP2A subunit interactions demonstrates that the B subunit plays a key role in directing the subcellular localization of PP2A, and confirms that the A subunit functions as a scaffold in recruiting the B and C subunits to form a heterotrimeric holoenzyme. BiFC analysis also reveals that α4 promotes formation of the AC core dimer. Furthermore, we demonstrate visualization of specific ABC holoenzymes in cells by combining BiFC and fluorescence resonance energy transfer (BiFC-FRET). Our studies not only provide direct imaging data to support previous biochemical observations on PP2A complexes, but also offer a promising approach for studying the spatiotemporal distribution of individual PP2A complexes in cells.     

The RNA-binding protein PCBP2 facilitates gastric carcinoma growth by targeting miR-34a

Gastric carcinoma is the fourth most common cancer worldwide, with a high rate of death and low 5-year survival rate. However, the mechanism underling gastric cancer is still not fully understood. Here in the present study, we identify the RNA-binding protein PCBP2 as an oncogenic protein in human gastric carcinoma. Our results show that PCBP2 is up-regulated in human gastric cancer tissues compared to adjacent normal tissues, and that high level of PCBP2 predicts poor overall and disease-free survival. Knockdown of PCBP2 in gastric cancer cells inhibits cell proliferation and colony formation in vitro, whereas opposing results are obtained when PCBP2 is overexpressed. Our in vivo subcutaneous xenograft results also show that PCBP2 can critically regulate gastric cancer cell growth. In addition, we find that PCBP2-depletion induces apoptosis in gastric cancer cells via up-regulating expression of pro-apoptotic proteins and down-regulating anti-apoptotic proteins. Mechanically, we identify that miR-34a as a target of PCBP2, and that miR-34a is critically essential for the function of PCBP2. In summary, PCBP2 promotes gastric carcinoma development by regulating the level of miR-34a.     

Biological and Molecular Characterization of Taiwanese Isolates of Cucumber mosaic virus Associated with Banana Mosaic Disease

Banana mosaic disease (BMD) caused by Cucumber mosaic virus (CMV) has become an important threat to the banana industry. We collected and characterized 10 CMV isolates associated with BMD in Taiwan and compared their biological characteristics and coat protein sequences. The isolates fell into four pathotypes on the basis of the symptoms they induce on banana, Nicotiana glutinosa and Vigna unguiculata (cowpea). Double-stranded RNA analysis revealed that the different pathotypes are not related to the presence of CMV satellite RNA. Phylogenetic analysis of worldwide CMV coat protein sequences revealed that among the currently known CMV subgroups IA, IB and II, subgroup IB is phylogenetically unresolved. Our CMV isolates form a new subgroup, IT, within subgroup I. In addition, we resolved another new CMV subgroup, IS, within subgroup I. The analysis also revealed that isolates within different subgroups can infect the banana.     

The Value of BISAP Score for Predicting Mortality and Severity in Acute Pancreatitis: A Systematic Review and Meta-Analysis

Purpose

The Bedside Index for Severity in Acute Pancreatitis (BISAP) score has been developed to identify patients at high risk for mortality or severe disease early during the course of acute pancreatitis. We aimed to undertake a meta-analysis to quantify the accuracy of BISAP score for predicting mortality and severe acute pancreatitis (SAP).

Materials and Methods

We searched the databases of Pubmed, Embase, and the Cochrane Library to identify studies using the BISAP score to predict mortality or SAP. The pooled sensitivity, specificity, likelihood ratios, and diagnostic odds ratio (DOR) were calculated from each study and were compared with the traditional scoring systems.

Results

Twelve cohorts from 10 studies were included. The overall sensitivity of a BISAP score of ≥3 for mortality was 56% (95% CI, 53%-60%), with a specificity of 91% (95% CI, 90%-91%). The positive and negative likelihood ratios were 5.65 (95% CI, 4.23-7.55) and 0.48 (95% CI, 0.41-0.56), respectively. Regarding the outcome of SAP, the pooled sensitivity was 51% (43%-60%), and the specificity was 91% (89%-92%). The pooled positive and negative likelihood ratios were 7.23 (4.21-12.42) and 0.56 (0.44-0.71), respectively. Compared with BISAP score, the Ranson criteria and APACHEⅡscore showed higher sensitivity and lower specificity for both outcomes.

Conclusions

The BISAP score was a reliable tool to identify AP patients at high risk for unfavorable outcomes. Compared with the Ranson criteria and APACHEⅡscore, BISAP score outperformed in specificity, but having a suboptimal sensitivity for mortality as well as SAP.     

不同生境条件下蕨类和被子植物的气孔形态特征及其对光强变化的响应

气孔是植物与大气环境进行气体交换的重要通道, 在调控植物碳水平衡方面发挥着重要作用。为探讨生境和植物类型对气孔形态特征的影响以及气孔对光强变化的响应格局在不同植物间和不同生境条件下的变异, 选取开阔生境和林下生境的5种蕨类植物和4种被子植物, 测定了它们的气孔形态特征和气孔导度对光强变化的响应。此外, 还收集了8篇文献中开阔和林下生境的45种蕨类植物和70种被子植物的气孔密度和气孔长度数据, 以增大样本量从而更好地探讨不同生境条件下蕨类和被子植物气孔密度及长度的变异格局, 并通过分析生境和植物类型对气孔形态特征的影响来推测生境和植物类型对气孔响应行为的可能影响。实验结果表明, 与林下植物相比, 开阔环境下的植物气孔密度更大, 气孔长度更小, 气孔对光强降低的响应更敏感; 但植物类型对气孔形态特征的影响以及对气孔响应光强的敏感程度的影响均不显著。对文献数据的分析表明, 生境和植物类型对气孔形态特征均有显著影响。考虑到气孔响应快慢与气孔形态特征密切相关, 与蕨类植物相比, 被子植物小而密的气孔可能为其更快地响应环境变化提供了基础。研究表明生境和植物类型对气孔响应行为均有显著影响。