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991.
利用Tn5定位诱变筛选紫云英根瘤菌Exo^—变种 总被引:1,自引:0,他引:1
利用Tn5定位诱变方法,对质粒pJBB5进行Tn5插入诱变,得到10个Tn5在59kbB5外源片段上有不同插入位点的质粒TN11,TN112,TN22,TN23,TN31,TN41,TN91,TN101,TN131,TN141。将Tn11等分别转移到已经含有不相容质粒pPH1JI的紫云英根瘤菌107菌株中,使之发生同源变换。通过抗性选择及表型鉴别,筛选到3株菌落表型干燥(Muc-)的酸性胞外多糖(EPS)合成缺陷菌株(Exo-)107(TN22),107(TN101),107(TN131)。Southern杂交分析证明这3株变种的Tn5插入确实是同源交换而不是转座产生,表明经过适当改良的Tn5定位诱变法可以应用于紫云英根瘤菌Exo-变种的筛选。 相似文献
992.
993.
Pei-Wen Chiang SuQing Wang Paul Smithivas Woo-Joo Song Saravanan Ramamoorthy Joseph Hillman Sheryl Puett Margaret L. Van Keuren Eric Crombez Arun Kumar Thomas W. Glover Diane E. Miller Chun-Hui Tsai C.Clare Blackburn Xiao-Ning Chen Zhiguang Sun Jan-Fang Cheng Julie R. Korenberg David M. Kurnit 《Genomics》1996,34(3):328
994.
Cd2+处理对菹草叶片保护酶活性和细胞超微结构的毒害影响 总被引:26,自引:2,他引:26
以不同浓度Cd^2 处理5d的菹草为实验材料,测定了叶片SOD,POD,CAT等生理生化指标的变化,并用透射电镜观察了Cd^2 对叶细胞超微结构,尤其是对叶绿体,线粒体和细胞核的损伤情况。结果表明:SOD活性,叶绿素含量随Cd^2 处理浓度的增加而下降,而CAT和POD活性都是在1mg/L浓度下达到峰值,而后降低。SOD对Cd^2 毒害最敏感,其次为POD和CAT。电镜观察发现:随Cd^2 浓度的增加,对细胞超微结构的损伤程度也加剧。表现为叶绿体膨大,被膜断裂、消失和叶绿体解体;线粒体变形,脊突膨大和空泡化;细胞核核仁分散,核膜断裂,核空泡化。并探讨了Cd^2 对植物的毒害机制。 相似文献
995.
The activities of antioxidant enzymes in response to oxidative stresses and hormones in paraquat-tolerant Rehmannia glutinosa plants 总被引:1,自引:0,他引:1
Choi DG Yoo NH Yu CY de Los Reyes B Yun SJ 《Journal of biochemistry and molecular biology》2004,37(5):618-624
All members of R. glutinosa show the unique characteristic of intrinsic tolerance to paraquat (PQ). Antioxidant enzymes have been proposed to be the primary mechanism of PQ resistance in several plant species. Therefore, the antioxidant enzyme systems of R. glutinosa were evaluated by comparatively analyzing cellular antioxidant enzyme levels, and their responses of oxidative stresses and hormones. The levels of ascorbate peroxidase (APX), glutathione reductase (GR), non-specific peroxidase (POX), and superoxide dismutase (SOD) were 7.3-, 4.9-, 2.7- and 1.6-fold higher in PQ-tolerant R. glutinosa than in PQ-susceptible soybeans. However, the activity of catalase (CAT) was about 12-fold higher in the soybeans. The activities of antioxidant enzymes reduced after PQ treatment in the two species, with the exception of POX and SOD in R. glutinosa, which increased by about 40 %. Interestingly, the activities of APX, SOD and POX in R. glutinosa, relative to those in soybeans, were further increased by 49, 67 and 93 % after PQ treatment. The considerably higher intrinsic levels, and increases in the relative activities of antioxidant enzymes in R. glutinosa under oxidative stress support the possible role of these enzymes in the PQ tolerance of R. glutinosa. However, the relatively lower levels of SOD versus PQ tolerance, and the mixed responses of antioxidant enzymes to stresses and hormones, suggest a possible alternative mechanism(s) for PQ tolerance in R. glutinosa. 相似文献
996.
喀斯特峰丛洼地不同类型森林群落的组成与生物多样性特征 总被引:3,自引:0,他引:3
不同退化程度石漠化生态重建的关键是恢复植被, 提高土地生产力。本文基于动态监测样地(200 m × 40 m)植被的全面调查, 研究了喀斯特峰丛洼地人工林、次生林和原生林3类典型森林群落木本植物的组成与生物多样性特征。结果表明, 3类森林的物种组成分别为26科52属65种、33科68属100种和43科91属123种, 常绿物种分别占41.54%、47.00%和52.85%; 科、属、种和生活型组成复杂, 优势科或种明显, TWINSPAN分类第3级水平上可分别划分为8、9和8个群落类型。原生林多样性和结构性指标均高于人工林和次生林, 人工林的Shannon-Wiener指数、Simpson指数、均匀度、冠幅、胸径和树高均高于次生林, 而种类、密度和盖度则低于次生林。不同类型森林群落特征不同, 应采取相应的经营策略。 相似文献
997.
Lee WS Lee DW Baek YI An S An SJ Cho KH Choi YK Kim HC Park HY Bae KH Jeong TS 《Bioorganic & medicinal chemistry letters》2004,14(12):3109-3112
The sesquineolignan, saucerneol B (1), and dineolignans, manassantin A (2), and manassantin B (3), were isolated from the methanol extracts of Saururus chinensis root and elucidated by their spectroscopic data analysis. Compounds 1-3 inhibited hACAT-1 and hACAT-2 with IC(50) values of 43.0 and 124.0 microM for 1, of 39.0 and 8.0 microM for 2, of 82.0 microM and only 32% inhibition at 1mM for 3, respectively. The EtOAc-soluble fraction, which contained compounds 1-3, of methanol extracts of S. chinensis exhibited strong cholesterol-lowering effect in high cholesterol-fed mice. 相似文献
998.
Cong-Ping Tan Fang-Qing Zhao Zhong-Liang Su Cheng-Wei Liang Song Qin 《Journal of applied phycology》2007,19(4):347-355
A carotenoid gene (crtR-B) from the green alga Haematococcus pluvialis, encoding β-carotene hydroxylase that was able to catalyze the conversion of β-carotene to zeaxanthin and canthaxanthin to
astaxanthin, was cloned into Chlamydomonas reinhardtii chloroplast expression vector p64D to yield plasmid p64DcrtR-B. The vector p64DcrtR-B was transferred to the chloroplast
genome of C. reinhardtii using micro-particle bombardment. PCR and Southern blot analyses indicated that crtR-B was integrated into the chloroplast genome of the transformants. RT-PCR assays showed that the H. pluvialis
crt R-B gene was expressed in C. reinhardtii transformants. The transformants rapidly synthesized carotenoids in larger quantities than the wild-type upon being transferred
from moderate to high-intensity white light. This research provides a foundation for further study to elucidate the possible
mechanism of photo-protection by xanthophylls and other carotenoids in high light conditions or through exposure to UV radiation. 相似文献
999.
H K Song J Y Lee M G Lee J Moon K Min J K Yang S W Suh 《Journal of molecular biology》1999,293(4):753-761
"Two-component" phosphorelay signal transduction systems constitute a potential target for antibacterial and antifungal agents, since they are found exclusively in prokaryotes and lower eukaryotes (yeast, fungi, slime mold, and plants) but not in mammalian organisms. Saccharomyces cerevisiae Ypd1p, a key intermediate in the osmosensing multistep phosphorelay signal transduction, catalyzes the phosphoryl group transfer between response regulators. Its 1.8 A structure, representing the first example of a eukaryotic phosphorelay protein, contains a four-helix bundle as in the HPt domain of Escherichia coli ArcB sensor kinase. However, Ypd1p has a 44-residue insertion between the last two helices of the helix bundle. The side-chain of His64, the site of phosphorylation, protrudes into the solvent. The structural resemblance between Ypd1p and ArcB HPt domain suggests that both prokaryotes and lower eukaryotes utilize the same basic protein fold for phosphorelay signal transduction. This study sheds light on the best characterized eukaryotic phosphorelay system. 相似文献
1000.
In vitro 5-day cultures of naive spleen cells with viable Listeria monocytogenes (VLM), but not heat-killed L. monocytogenes, induced CD4+ T cells that produced IFN-γ upon secondary antigen stimulation. The VLM-induced Listeria-specific T cells produced IFN-γ but lacked expression of IL-2 and IL-4. To study the role of IFN-γ in the induction of the IFN-γ-producing T cells, we added anti-IFN-γ mAb to the primary culture and analyzed IFN-γ production upon secondary antigen stimulation. Addition of anti-IFN-γ mAb to the culture suppressed generation of IFN-γ-producing CD4+ T cells, suggesting that IFN-γ is important in the induction of IFN-γ-producing CD4+ T cells. Furthermore, our results showed that depletion of NK cells from spleen cells by anti-asialo GM1 antibody plus complement before culture enhanced induction of IFN-γ-producing CD4+ T cells. Although NK cells are known to produce IFN-γ, the results indicate that NK cell-derived IFN-γ may not be important in induction of the Listeria-specific IFN-γ-producing CD4+ T cells in the culture system. In addition, we demonstrated that IFN-γ expression was high in CD4+ T cells from cultures of spleen cells with VLM at the primary culture level. These results suggest that IFN-γ derived from T cells may enhance production of IFN-γ by CD4+ T cells, while NK cells rather suppress the induction of IFN-γ-producing CD4+ T cells. 相似文献