Feedback from Lateral Organs Controls Shoot Apical Meristem Growth by Modulating Auxin Transport

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异叶银合欢根瘤菌的分离和特性

从异叶银合欢K(164)和K(794)的根瘤中各分离到一株根瘤菌,并且,对K164根瘤菌的形态特征和生理生化特性进行了研究。K(164)根瘤菌在平板上培养2天,菌落呈圆形,灰白色,直径约1．2mm;革兰氏染色呈阴性,无芽孢,有美膜,两根极生鞭毛;杆菌大小为2．2×0．89μm,增代时间为1．69小时,属快生型;最适生长温度为30℃,在39℃持续2天不能存活,在20℃以下不能生长;不耐盐,较耐酸,在pH4.5～6．6范围内均能生长,但不耐碱;对庆大霉素和青霉素敏感;对供试的10种糖都能利用,不液化明胶,不利用淀粉,B．T．B试验未变色,不能进行3-酮基乳糖反应,硝酸盐反应呈阳性,石蕊牛奶试验能胨化、还原、产碱,牛肉膏蛋白胨培养生长差,能利用柠檬酸盐;在自生条件下具有吸H2酶活性;回接后结瘤率达100％,根瘤具有固氮酶和吸H2酶活性。     

循环水养殖系统中凡纳滨对虾肠道微生物对三种复合益生菌制剂的响应

【目的】在循环养殖系统中应用不同的复合益生菌制剂,探讨凡纳滨对虾肠道菌群结构特征及免疫水平发生的变化。【方法】30 d养殖周期结束后,通过平板计数法分析肠道细菌总数和弧菌总数;基于高通量测序技术分析肠道样品V3+V4区菌群特征;采用实时荧光定量PCR技术分析免疫相关因子TLR1和Dorsal基因表达水平,阐述益生菌制剂应用的意义。【结果】益生菌制剂的应用降低了凡纳滨对虾肠道中细菌总数,抑制弧菌的生长,间接预防疾病的发生。不同益生菌制剂从不同程度上优化了凡纳滨对虾肠道菌群结构,提高高质量序列和有效OTU数量,Chao1、Simpson、Shannon指数显示了丰富度和多样性变化,复合益生菌制剂3效果较好。同时,菌群结构得到优化,其中益生菌制剂1组对拟杆菌门含量百分比产生显著影响。Toll受体TLR1和Toll通路中的Dorsal基因m RNA表达受到益生菌制剂的影响,1、3组促进了TLR 1表达,1、2、3组都促进了Dorsal基因表达。【结论】在循环水养殖系统中添加益生菌制剂可优化凡纳滨对虾肠道菌群特征,提高免疫水平,为病害防控和健康养殖提供理论依据。     

大剂量国产胸腺肽联合干扰素治疗慢性乙肝疗效及其机理初探

本文研究大剂量胸腺肽联合干扰素对慢性乙肝患者的治疗作用,发现胸腺肽联合干扰素治疗三个月后,患者的ＡＬＴ复常率、ＨＢｅＡｇ转阴率、ＨＢＶＤＮＡ阴转率和ＨＢＶＤＮＡ有效下降率分别为７６０％、４４０％、５６０％和９６０％。Ｔ淋巴细胞亚群分析结果表明,联合治疗后,患者外周血ＣＤ４＋淋巴细胞亚群上调,ＣＤ８＋亚群下调,二者比值趋于正常,说明国产胸腺肽联合干扰素治疗慢性乙肝的治疗机理与免疫调节作用有关。     

Structural definition of the C5a C terminus by two-dimensional nuclear magnetic resonance spectroscopy

The serum glycoprotein C5a, which is derived from the proteolytic cleavage of complement protein C5, has been implicated in the pathogenesis of a number of inflammatory and allergic conditions. Because C5a induces an inflammatory response upon binding to a specific receptor, structural and mutagenesis studies were carried out to gain a better understanding of this binding interaction. These studies led to the first structural definition of the C terminus of recombinant human (rh)-C5a, determined by two-dimensional nuclear magnetic resonance (NMR) spectroscopy. Our results show that the C terminus adopts an α-helical conformation spanning residues 69 to 74, while the core domain exists as an antiparallel α-helical bundle. This C-terminal helix is connected to the core by a short loop that orients Arg 74 adjacent to Arg 62. Point mutation analysis had already revealed that residues 62 and 74 significantly contribute to agonist activity and receptor binding. Correlation of the C5a tertiary structure with mutational analyses clarifies the significance of the functional and binding properties of Arg 62 and suggests that both Arg 62 and Arg 74 interact at the same binding site on the receptor. Proteins 28:261–267, 1997 © 1997 Wiley-Liss Inc.     

Calcium imaging in Arabidopsis pollen cells using G-CaMP5

Calcium(Ca~(2+)) signaling has been implicated in pollen germination and pollen tube growth. To date,however, we still know very little about how exactly Ca~(2+) signaling links to various physiological subcellular processes during pollen germination and pollen tube growth.Given that Ca~(2+) signaling is tightly related to the cytosolic concentration and dynamics of Ca~(2+), it is vital to trace the dynamic changes in Ca~(2+) levels in order to decode Ca~(2+) signaling. Here, we demonstrate that G-Ca MP5 serves well as an indicator for monitoring cytosolic Ca~(2+) dynamics in pollen cells. Using this probe, we show that cytosolic Ca~(2+) changes dramatically during pollen germination, and, asreported previously, Ca~(2+) forms a tip-focused gradient in the pollen tube and undergoes oscillation in the tip region during pollen tube growth. In particular, using G-CaMP5 allowed us to capture the dynamic changes in the cytosolic Ca~(2+) concentration([Ca~(2+)]_(cyt)) in pollen tubes in response to various exogenous treatments. Our data suggest that G-CaMP5 is a suitable probe for monitoring the dynamics of[Ca~(2+)]_(cyt) in pollen cells.     

Molecular Characterization of the Total Bacteria and Dissimilatory Arsenate-Reducing Bacteria in Core Sediments of the Jianghan Plain,Central China

Arsenic contamination in groundwater has been reported in the Jianghan Plain of China since 2005, yet little is known about the microbial communities involved in As mobilization in this area, especially the dissimilatory arsenate-reducing bacteria (DARB) communities. Here, we conducted a cultivation-independent investigation on core sediments collected from a region with arsenic-contaminated groundwater in the Jianghan Plain to reveal the total bacteria and DARB community structures. Highly diverse As-resistant bacteria communities were found from sediment samples via high-throughput sequencing of 16S rRNA genes. Notably, we identified 27 unique arrA gene (encoding the alpha subunit of dissimilatory arsenate reductase) phylotypes, none of which was related to any previously described arrA gene sequence. This suggests a novel and unique DARB community in the sediments of the Jianghan Plain and expands our knowledge about the distribution and diversity of this group of bacteria in natural environments. Moreover, RDA and CCA demonstrated that total bacterial communities and specific functional groups are controlled by different environmental factors. Specifically, sediment pH, NH₄⁺, total nitrogen, total Fe, total organic carbon and total phosphorus were the key factors driving total bacterial community compositions, while As significantly shaped DARB community structures. This report is the first to describe DARB communities and their correlation with environmental factors in Jianghan Plain sediments, which could give us clues about the origin of the arsenic contamination of groundwater in this region.