诺卡氏菌属GS-17耐热茁霉多糖酶的提纯和性质

诺卡氏菌属GS-17(Nocardia sp.GS-17)的耐热茁霉多糖酶(Pullulanase EC.3.2.1.41)的粗酶液经中空纤维柱超滤浓缩、羟基磷灰石柱层析和Pullulan-Sepharose 6B亲和层析,得到凝胶电泳均一的纯酶,比活提高264倍.酶作用最适温度为55℃,最适PH6.2,分子量140000,等电点pI为6.0.该酶水解茁霉多糖、支链淀粉和可溶性淀粉,但不水解糖原.酶在50℃作用于茁霉多糖的米氏常数K_m为0.90mg/ml,最大反应速度V_(max)为57μmol·min~(-1)·mg~(-1).Zn~(2 )、Fe~(3 )、Hg~(2 )、Cu~(2 )、Pb~(2 )和环状糊精对酶有抑制作用,Ca~(2 )对酶有激活作用.经蛋白质侧链化学修饰研究表明,色氨酸残基位于酶的活性位区.该酶是由1129个氨基酸残基组成的单肽链,酶的N末端序列经测定为:Ala-Gly-His-Gly-Pro-Asp-Val-Gln-Asp-Gly-     

天目山常绿落叶阔叶林群落垂直结构与群落整体物种多样性的关系

以浙江省天目山1 hm²常绿落叶阔叶混交林样地调查数据为基础,运用K-means聚类方法将DBH≥1 cm的个体根据树高划分为不同林层,研究比较了各个林层的物种多样性特点;利用通径分析方法和决策系数定量计算各个林层物种多样性对群落整体物种多样性的直接作用和间接作用,天目山常绿落叶阔叶林垂直结构对群落物种多样性构成的影响。结果表明：（1）天目山常绿落叶阔叶林群落层次结构丰富,树高由1.4-36.5 m依次可分为灌木层、亚冠层、林冠下层、林冠中层和林冠上层。（2）天目山常绿落叶阔叶林群落从灌木层依次往向上,物种丰富度、多度、特有种数量、Shannon-Weiner指数和Simpson指数均呈下降趋势。（3）灌木层对群落物种多样性的贡献最大且远高于其他四个林层,其中灌木层对群落整体物种多样性Shannon-Wiener指数、Pielou指数以及Simpson指数的决策系数分别为0.850、0.651、0.755。（4）林冠下层、林冠中层和林冠上层密度的大小对灌木层的物种数目有明显的影响,林冠层密度越大,灌木层群落的物种数目越少,复杂程度越低;偶见种和稀有种对群落物种多样性的维持具有特殊作用。综上,研究认为森林群落的垂直结构在维持森林群落整体物种多样性中具有关键作用,而灌木层在群落整体物种多样性构成中具有决定作用,森林群落中稀有种、偶见种多少在群落物种多样性构成中具有特殊作用。     

The MET13 Methylenetetrahydrofolate Reductase Gene Is Essential for Infection-Related Morphogenesis in the Rice Blast Fungus Magnaporthe oryzae

Methylenetetrahydrofolate reductases (MTHFRs) play a key role in the biosynthesis of methionine in both prokaryotic and eukaryotic organisms. In this study, we report the identification of a novel T-DNA-tagged mutant WH672 in the rice blast fungus Magnaporthe oryzae, which was defective in vegetative growth, conidiation and pathogenicity. Analysis of the mutation confirmed a single T-DNA insertion upstream of MET13, which encodes a 626-amino-acid protein encoding a MTHFR. Targeted gene deletion of MET13 resulted in mutants that were non-pathogenic and significantly impaired in aerial growth and melanin pigmentation. All phenotypes associated with Δmet13 mutants could be overcome by addition of exogenous methionine. The M. oryzae genome contains a second predicted MTHFR-encoding gene, MET12. The deduced amino acid sequences of Met13 and Met12 share 32% identity. Interestingly, Δmet12 mutants produced significantly less conidia compared with the isogenic wild-type strain and grew very poorly in the absence of methionine, but were fully pathogenic. Deletion of both genes resulted in Δmet13Δmet12 mutants that showed similar phenotypes to single Δmet13 mutants. Taken together, we conclude that the MTHFR gene, MET13, is essential for infection-related morphogenesis by the rice blast fungus M. oryzae.     

Origin and differentiation of endemism in the flora of China

The present paper analyzed 239 endemic genera in 67 families in the flora of seed plants in China.The results showed that there are five families containing more than ten endemic genera,namely,Gesneriaceae (27),which hereafter refers to the number of endemic genera in China,Composite (20),Labiatae (12),Cruciferae (11),and Umbelliferae (10),15 families with two endemic genera,and another 30 families with only one endemic genus.Four monotypic families (Ginkgoaceae,Davidiaceae,Eucommiaceae and Acanthochlamydaceae)are the most ancient,relict and characteristic in the flora of seed plants in China.Based on integrative data of systematics,fossil history,and morphological and molecular evidence of these genera,their origin,evolution and relationships were discussed.In gymnosperms,all endemic genera are relicts of the Arctic-Tertiary flora,having earlier evolutionary history,and can be traced back to the Cretaceous or to the Jurassic and even earlier.In angiosperms,the endemic genera are mostly relicts,and are represented in all lineages in the"Eight-Class System ofClassification of Angiosperms",and endemism can be found in almost every evolutionary stage of extant angiosperms.The relict genera once occupied huge areas in the northern hemisphere in the Tertiary or the late Cretaceous,while neo-endemism mostly originated in the late Tertiary.They came from Arctic-Tertiary,Paleo-tropical-Tertiary and Tethys-Tertiary florisitic elements,and the blend of the three elements with many genera of autochthonous origin.The endemism was formed when some dispersal routes such as the North Atlantic Land Bridge,and the Bering Bridge became discontinuous during the Tertiary,as well as the climate change and glaciations in the late Tertiary and the Quaternary.Therefore,the late Tertiary is the starting point of extant endemism of the flora in China.     

N-glycan branching requirement in neuronal and postnatal viability

The structural variations among extracellular N-glycans reflect the activity of glycosyltransferases and glycosidases that operate in the Golgi apparatus. More than other types of vertebrate glycans, N-glycans are highly branched oligosaccharides with multiple antennae linked to an underlying mannose core structure. The branching patterns of N-glycans consist of three types, termed high-mannose, hybrid, and complex. Though most extracellular mammalian N-glycans are of the complex type, some cells variably express hybrid and high-mannose forms. Nevertheless, a requirement for hybrid and complex N-glycan branching exists in embryonic development and postnatal function among mice and humans inheriting defective Mgat1 or Mgat2 alleles. The resulting defects in formation N-glycan branching patterns cause multiple abnormalities, including neurologic defects, and have inferred the presence of distinct functions for hybrid and complex N-glycan branches among different cell lineages. We have further explored N-glycan structure-function relationships in vivo by using Cre-loxP conditional mutagenesis to abolish hybrid and complex N-glycan branching specifically among neuronal cells. Our findings show that hybrid N-glycan branching is an essential posttranslational modification among neurons. Loss of Mgat1 resulted in a unique pattern of neuronal glycoprotein deficiency concurrent with caspase 3 activation and apoptosis. Such animals exhibited severe locomotor deficits, tremors, paralysis, and early postnatal death. Unexpectedly, neuronal Mgat2 deletion resulting in the loss of complex but not hybrid N-glycan branching was well tolerated without phenotypic markers of neuronal or locomotor dysfunction. Structural features associated with hybrid N-glycan branching comprise a requisite posttranslational modification to neuronal glycoproteins that permits normal cellular function and viability.     

江淮丘陵地区油-稻轮作条件下土壤硫库变化研究

江淮丘陵地区下蜀系黄土母质发育的水稻土油2稻轮作试验表明, 油菜种植期间, 耕层土壤硫主要来源于耕层以下土层的补给, 其次是大气干湿沉降;该时期耕层土壤硫输出主要是油菜吸收, 其次是淋失.油菜种植期间耕层土壤硫输入量小于输出, 导致耕层土壤硫库下降8.76kg·hm^-2, 22%来自无机硫库的下降.水稻种植期间, 耕层土壤硫输入主要来自灌溉水, 其次是底土层的补给和大气干湿沉降;而硫输出主要是淋失, 其次是水稻吸收.耕层土壤硫输入量大于输出, 导致耕层土壤硫库增加18.69kg·hm^-2, 18%来自无机硫库的增加.全年油2稻轮作期间耕层土壤硫输入量大于输出, 导致耕层土壤硫库增加9.93kg·hm^-2, 13%来自无机硫库的增加.     

Prognostic Value of Cancer Stem Cell Marker ALDH1 Expression in Colorectal Cancer: A Systematic Review and Meta-Analysis

Objective

Many studies have indicated the prognostic and clinicopathological value of aldehyde dehydrogenase 1 (ALDH1) in colorectal cancer (CRC) patients still remains controversial. Thus we performed this study to clarify the relationship between high ALDH1 expression in CRC and its impact on survival and clinicopathological features.

Methods

Publications for relevant studies in Pubmed, the Cochrane Library, Embase, and China National Knowledge Infrastructure (CNKI) through April 2015 were identified. Only articles describing ALDH1 antigen with immunohistochemistry in CRC were included. The software RevMan 5.1 was used to analyze the outcomes, including 5-year overall survival (OS), disease-free survival (DFS) and clinicopathological features.

Results

9 studies with 1203 patients satisfying the criteria were included. The overall rate of high ALDH1 expression was 46.5% by immunohistochemical staining. High ALDH1 expression as an independent prognostic factor was significantly associated with the 5-year OS and DFS (OR = 0.42, 95%CI: 0.26–0.68, P = 0.0004; OR = 0.38, 95%CI: 0.24–0.59, P < 0.0001, respectively). High ALDH1 expression was highly correlated with the tumor (T) stage (T3 + T4 vs. T1 + T2; OR = 2.16, 95%CI: 1.09–4.28, P = 0.03), lymph node (N) stage (N1 + N2 vs. N0; OR = 1.8; 95%CI: 1.17–2.79, P = 0.008), and tumor differentiation (G3 vs. G1 + G2; OR = 1.88; 95%CI: 1.07–3.30, P = 0.03). However, high ALDH1 expression was not significantly correlated with the patient age (>60 years old vs. <60 years old; OR = 1.11, 95%CI: 0.63–1.94, P = 0.72).

Conclusions

High ALDH1 expression indicates a poor prognosis in CRC patients. Moreover, high ALDH1 expression correlates with the T stage, N stage, and tumor differentiation, but not with age.