炭角菌科部分类群的生物地理学研究(英文)

与肉质真菌相比,大多数炭角菌科真菌的子实体结构和质地使其在自然环境中保持长久,不易腐变,这有利于记录该科采集物的分布信息,基于过去长达25年对该科的深厚工作积累,使我们有可能对其进行地理分布的研究。     

Complex phylogenetic distribution of a non-canonical genetic code in green algae

Background  

A non-canonical nuclear genetic code, in which TAG and TAA have been reassigned from stop codons to glutamine, has evolved independently in several eukaryotic lineages, including the ulvophycean green algal orders Dasycladales and Cladophorales. To study the phylogenetic distribution of the standard and non-canonical genetic codes, we generated sequence data of a representative set of ulvophycean green algae and used a robust green algal phylogeny to evaluate different evolutionary scenarios that may account for the origin of the non-canonical code.     

An observation on the influence of nitrogen fertilization on the attack of peas by powdery mildew (Erysiphe polygoni DC)

Summary A pot experiment with peas var. Pauli is described in which it was observed that plants fertilized with NH₄NO₃ were much less attacked by powdery mildew than those which did not receive any nitrogen.     

Identification and Characterisation of the RalA-ERp57 Interaction: Evidence for GDI Activity of ERp57

RalA is a membrane-associated small GTPase that regulates vesicle trafficking. Here we identify a specific interaction between RalA and ERp57, an oxidoreductase and signalling protein. ERp57 bound specifically to the GDP-bound form of RalA, but not the GTP-bound form, and inhibited the dissociation of GDP from RalA in vitro. These activities were inhibited by reducing agents, but no disulphide bonds were detected between RalA and ERp57. Mutation of all four of ERp57’s active site cysteine residues blocked sensitivity to reducing agents, suggesting that redox-dependent conformational changes in ERp57 affect binding to RalA. Mutations in the switch II region of the GTPase domain of RalA specifically reduced or abolished binding to ERp57, but did not block GTP-specific binding to known RalA effectors, the exocyst and RalBP1. Oxidative treatment of A431 cells with H₂O₂ inhibited cellular RalA activity, and the effect was exacerbated by expression of recombinant ERp57. The oxidative treatment significantly increased the amount of RalA localised to the cytosol. These findings suggest that ERp57 regulates RalA signalling by acting as a redox-sensitive guanine-nucleotide dissociation inhibitor (RalGDI).     

Stalk Formation and Its Inhibition in Caulobacter crescentus

Estimates of average rates of stalk formation over several generations of growth in Caulobacter crescentus showed that long-stalked Sk1 mutant and phosphate-starved wild-type cultures produce stalk material at about twice the rate of wild-type C. crescentus grown with adequate nutrients. Thus, the long stalks of Sk1 or phosphate-starved caulobacters are not merely a function of their longer doubling times. Inhibition of cell division of Sk1 418 with mitomycin C (MC) caused production of cellular filaments and resulted in inhibition of stalk formation. There was no appreciable decrease in total cell mass or in rates of ribonucleic acid and protein synthesis in the MC-treated cultures as compared with controls, but stalk formation, which is normally dependent on these processes, was severely retarded. Average stalk lengths in MC-treated Sk1 cultures were 30% of those found in control cultures. MC-produced cellular filaments were also subjected to deoxyribonucleic acid analysis and ultrastructural examination. The deoxyribonucleic acid content of MC-treated bacteria was about 50 to 60% that of untreated bacteria. Hydroxyurea also was found to produce some cellular filaments and shorter stalks, but with accompanying decreases in growth rate and yield.     

Food availability affects the strength of mutualistic host–microbiota interactions in Daphnia magna

The symbiotic gut microbial community is generally known to have a strong impact on the fitness of its host. Nevertheless, it is less clear how the impact of symbiotic interactions on the hosts'' fitness varies according to environmental circumstances such as changes in the diet. This study aims to get a better understanding of host–microbiota interactions under different levels of food availability. We conducted experiments with the invertebrate, experimental model organism Daphnia magna and compared growth, survival and reproduction of conventionalized symbiotic Daphnia with germ-free individuals given varying quantities of food. Our experiments revealed that the relative importance of the microbiota for the hosts'' fitness varied according to dietary conditions. The presence of the microbiota had strong positive effects on Daphnia when food was sufficient or abundant, but had weaker effects under food limitation. Our results indicate that the microbiota can be a potentially important factor in determining host responses to changes in dietary conditions. Characterization of the host-associated microbiota further showed that Aeromonas sp. was the most prevalent taxon in the digestive tract of Daphnia.     

IL-28A,IL-28B,and IL-29: Promising cytokines with type I interferon-like properties

IL-28A, IL-28B and IL-29 (also designated type III interferons) constitute a new subfamily within the IL-10–interferon family. They are produced by virtually any nucleated cell type, particularly dendritic cells, following viral infection or activation with bacterial components, and mediate their effects via the IL-28R1/IL-10R2 receptor complex. Although IL-28/IL-29 are closer to the IL-10-related cytokines in terms of gene structure, protein structure, and receptor usage, they display type I interferon-like anti-viral and cytostatic activities. Unlike type I interferons, the target cell populations of IL-28/IL-29 are restricted and mainly include epithelial cells and hepatocytes. These properties suggest that IL-28/IL-29 are potential therapeutic alternatives to type I interferons in terms of viral infections and tumors. This review describes the current knowledge about these cytokines.