水鳖蕨配子体系统学特征的培养观察

在光学显微镜下观察了水鳖蕨(Sinephropteris delavayi(Franch.)Mickel)配子体发育的详细过程。水鳖蕨孢子培养6 d左右萌发;原丝体单列细胞,或发育出2~3个分支;片状体生长点不明显,成熟配子体近心形。本文还讨论了其生长点、毛状体及性器的发育特点,结果支持Mickel将水鳖蕨独立成属的观点。     

Cardioprotection in ischemia/reperfusion injury: Spotlight on sphingosine-1-phosphate and bradykinin signalling

Complex signal-transduction cascades are known to be involved in regulating cardiomyocyte function, death and survival during acute cardiac ischemia-reperfusion process, but detailed survival signalling pathways are not clear. This review presents and discusses the recent findings bearing upon the evidence on the cardioprotective effect of sphingosine-1-phosphate (S1P) and bradykinin in acute cardiac ischemia-reperfusion and underlying signalling mechanisms, particularly, through activation of P21 activated kinase.     

The alternative pathway in cucumber seedlings under low temperature stress was enhanced by salicylic acid

The alternative pathway is a cyanide-resistant and non-phosphorylatory electron transport pathway in mitochondria of higher plants. Alternative oxidase (AOX) is the terminal oxidase of this pathway. Our present study investigated the effect of exogenous salicylic acid (SA) on alternative pathway in cucumber (Cucumis sativus L.) seedlings under low temperature stress. Results showed that during the process of low temperature stress, the alternative pathway capacity was enhanced as AOX expression increased in SA pretreated seedlings. Compared with seedlings without SA pretreatment, slower decrease of relative water content and lower levels of electrolyte leakage, H₂O₂ and malonyldialdehyde content were detected in SA pretreated seedlings. These results indicated that SA could alleviate the injury caused by low temperature on cucumber seedlings. Since the special protective functions of alternative pathway and AOX in plants, we suggested that the alternative pathway was related to SA-mediated plant resistance to environmental stresses such as low temperature.     

Functional characterization of the translationally controlled tumor protein (<Emphasis Type="Italic">TCTP</Emphasis>) gene associated with growth and defense response in cabbage

The translationally controlled tumor protein (TCTP) is an important component of the target of rapamycin (TOR) signaling pathway, the major regulator of cell growth in animals and fungi. Despite its relevance, knowledge on plant TCTP homologs is still limited. In the present study, the full-length BoTCTP cDNA was isolated from a cabbage (Brassica oleracea L.) cDNA library. The BoTCTP cDNA encodes a polypeptide of 168 amino acids and shared the highly conserved GTPase binding surface in all of the species analyzed. Northern blotting analysis showed that BoTCTP was specifically expressed in the root and stem. Furthermore, the expression of BoTCTP could be obviously enhanced by stress stimuli, including high temperature and salt stresses, while no significant changes in the BoTCTP expression were observed under ABA stress. Functional analysis of BoTCTP was performed by the silencing of BoTCTP using RNA interference (RNAi) and the BoTCTP RNAi plants exhibited reduced vegetative growth rate and decreased tolerance of the cold, high temperature, and salt stresses. The reported results clearly suggest that the BoTCTP gene is involved in the regulation of both growth and stress response in cabbage.     

A multiplex PCR method to detect 14 Escherichia coli serogroups associated with urinary tract infections

Urinary tract infections (UTIs) are one of the most common bacterial infections and are predominantly caused by uropathogenic Escherichia coli (UPEC). E. coli strains belonging to 14 serogroups, including O1, O2, O4, O6, O7, O8, O15, O16, O18, O21, O22, O25, O75 and O83, are the most frequently detected UPEC strains in a diverse range of clinical urine specimens. In the current study, the O-antigen gene clusters of E. coli serogroups O1, O2, O18 and O75 were characterized. A multiplex PCR method based on O-antigen-specific genes was developed for the simultaneous detection of all 14 E. coli serogroups. The multiplex PCR method was shown to be highly specific and reproducible when tested against 186 E. coli and Shigella O-serogroup reference strains, 47 E. coli clinical isolates and 10 strains of other bacterial species. The sensitivity of the multiplex PCR method was analyzed and shown to detect O-antigen-specific genes in samples containing 25 ng of genomic DNA or in mock urine specimens containing 40 colony-forming units (CFUs) per ml. Five urine specimens from hospital were examined using this multiplex PCR method, and the result for one sample was verified by the conventional serotyping methods. The multiplex PCR method developed herein can be used for the detection of relevant E. coli strains from clinical and/or environmental samples, and it is particularly useful for epidemiologic analysis of urine specimens from patients with UTIs.     

Enhancement of the innate immune response of bladder epithelial cells by Astragalus polysaccharides through upregulation of TLR4 expression

The innate host defenses at mucosal surfaces are critical in the early stages of urinary tract bacterial infection. Recent studies have shown that uroepithelial cells aid innate immune cells in fighting off infection, although the exact mechanism by which the uroepithilium participates in immunity remains unclear. TLR4 has been implicated to possess antimicrobial activities specific for bladder epithelial cells (BECs). TLR4 promotes secretion of IL-6 and IL-8, mediates inhibition of bladder epithelial cell (BEC) bacterial invasion, and mediates expulsion of uropathogenic Escherichia coli from BECs. In this study, cultured 5637 cells and Balb/C mice were treated with Astragalus polysaccharides (APS) against invading E. coli. To determine the contribution of TLR4 upregulation to immune response, TLR4 expression and bacterial colony numbers were monitored. After 24 h incubation, only 5637 cells treated with 500 μg/ml APS expressed higher levels of TLR4 compared with the untreated group. However, after 48 h, all 5637 cells treated by APS showed higher levels of TLR4 expression than the control cells. The TLR4 expression in the bladder and macrophages mice that received APS was higher than that in the controls. Bacterial colonization in 5637 cells and the bladders of mice treated with APS was significantly reduced compared with the controls. These results demonstrate that at certain concentrations, APS can induce increased TLR4 expression in vivo and in vitro. Further, TLR4 expression upregulation can enhance innate immunity during mucosal bacterial infection. The findings establish the use of APS to modulate the innate immune response of the urinary tract through TLR4 expression regulation as an alternative option for UTI treatment.     

The proline/arginine-rich domain is a major determinant of dynamin self-activation

Dynamins induce membrane vesiculation during endocytosis and Golgi budding in a process that requires assembly-dependent GTPase activation. Brain-specific dynamin 1 has a weaker propensity to self-assemble and self-activate than ubiquitously expressed dynamin 2. Here we show that dynamin 3, which has important functions in neuronal synapses, shares the self-assembly and GTPase activation characteristics of dynamin 2. Analysis of dynamin hybrids and of dynamin 1-dynamin 2 and dynamin 1-dynamin 3 heteropolymers reveals that concentration-dependent GTPase activation is suppressed by the C-terminal proline/arginine-rich domain of dynamin 1. Dynamin proline/arginine-rich domains also mediate interactions with SH3 domain-containing proteins and thus regulate both self-association and heteroassociation of dynamins.     

Effects of ecological environment and host genotype on the phyllosphere bacterial communities of cigar tobacco (Nicotiana tabacum L.)

Microorganisms of plant phyllosphere play an important role in plant health and productivity and are influenced by abiotic and biotic factors. In this study, we investigated the phyllosphere bacterial communities of three cigar tobacco varieties cultivated in Guangcun (GC) and Wuzhishan (WZS), Hainan, China. Metagenomic DNA was extracted from tobacco leaf samples and sequenced by 16S rDNA amplicon sequencing. Our results showed that bacterial communities of cigar tobacco phyllosphere in GC exhibited remarkably higher alpha diversity than that in WZS. There was slight effect of tobacco genotype variations on the alpha diversity in both cultivation sites, and beta diversity and structure of bacterial community were not influenced significantly by the cultivation sites and tobacco varieties. Statistical analyses of species diversity unraveled that the dominant species in bacterial communities of cigar tobacco phyllosphere among all these samples were phylogenetically affiliated to Proteobacteria and Cyanobacteria. At the genus level, the most abundant microorganism was Limnobacter, followed by Brevundimonas, unidentified_Cyanobacteria, and Pseudomonas. Additionally, environmental conditions except for humidity were negatively correlated with the relative abundance of bacterial genera. Further analyses revealed that influence of site‐specific factors on tobacco bacterial community was relatively higher than genotype‐specific factors. In short, this study may contribute to the knowledge base of practical applications of bacterial inoculants for tobacco leaf production.     

Conformational rearrangements to the intracellular open states of the LeuT and ApcT transporters are modulated by common mechanisms

Recent crystallographic studies revealed that five transporter families without much sequence similarities among them have similar structure folds to LeuT, a bacterial neurotransmitter:sodium symporter homolog. The LeuT fold is characterized by an internal twofold structural pseudosymmetry. The transport cycle of some members of each of these families is dependent on a sodium gradient across the membrane, whereas in some others the role of sodium is mimicked by proton. We report on the identification of common structure-dynamics elements of the transporters with LeuT fold, which are recognizable in the conformational transitions related to function. The findings from comparative computational modeling and simulation studies of LeuT, and ApcT from the amino acid-polyamine-organocation transporter family define the intramolecular mechanisms by which Na⁺ binding couples to the transport process, and single out the lead/active role of TM1a in the transition to inward-open conformation. These mechanistic insights are derived in the context of collaborative investigations of LeuT dynamics with both single-molecule fluorescence and simulations that have produced excellent agreement of the dynamic details, and are found to be generalizable across the transporter families and to transcend sequence and motif similarities.