Nitrate reductase activity of nonmycorrhizal Douglas-fir rootlets and of some associated mycorrhizal fungi

Douglas-fir root tips reduced nitrate at much higher rates than seven mycorrhizal fungi, which also differed between species in rate of nitrate reduction. Results are related to nitrogen nutrition of Douglas-fir.Excised, nonmycorrhizal root tips of Douglas-fir reduced nitrate at much higher rates than seven mycorrhizal fungi commonly associated with Douglas-fir. The fungi differed significantly in degree of activity:Cenococcum geophilum, Piloderma bicolor, andRhizopogon vinicolor were highest;Amanita muscaria was intermediate; andHebeloma crustuliniforme, Thelephora terrestris, andLaccaria laccata were lowest.     

Phylogenetic divergence in a local population of the ectomycorrhizal fungus Cenococcum geophilum

Cenococcum geophilum is a widely distributed mycorrhizal species associated with diverse gymnosperm and angiosperm hosts. In previous studies, a significant amount of genetic and genotypic diversity has been detected in this species, despite the fact that C. geophilum is not thought to reproduce by meiotic or mitotic spores. We conducted a phylogenetic analysis of 103 C. geophilum isolates from a California oak woodland and seven non-California isolates using a glyceraldehyde 3-phosphate dehydrogenase gene. In addition, a subset of isolates was analyzed using sequences from ITS-rDNA, a Group I intron located in the 3' end of the SSU-rDNA and a portion of the mitochondrial SSU-rDNA. Phylogenetically distinct lineages, or cryptic species, of C. geophilum were detected at the scale of a single soil sample within our field site. As much genetic diversity was found within a soil sample as was found for isolates collected across the USA. Our results help explain the large amount of physiological, phenotypic, and genetic differences reported among isolates of C. geophilum from similar as well as diverse geographic regions. The ecological role that these sympatric cryptic species play remains to be determined.     

Evidence of species interactions within an ectomycorrhizal fungal community

Ectomycorrhizal fungal communities can be structured by abiotic and biotic factors. Here, we present evidence for community structuring by species interactions. We sampled ectomycorrhizas and forest floor seven times during a 13-month period. The presence of various ectomycorrhizal fungal species was determined for each sample, and species co-occurrence analyses were performed. For both ectomycorrhizas and forest floor samples there was significantly less co-occurrence among species within the community than expected by chance, mostly because of negative associations involving Cenococcum geophilum or Clavulina cinerea. For some species pairs, there was significantly more co-occurrence than expected by chance. Both nitrogen and tannin additions to the forest floor altered some interactions among species. The causes of these nonrandom distributions are currently unknown. Future investigations on competition, antibiosis, parasitism and facilitation among ectomycorrhizal fungal species appear to be warranted.     

土生空团菌的遗传多样性分析

为了研究土生空团菌的遗传多样性,对来自中国、美国、瑞士和法国等菌株的rDNA ITS区进行序列分析,利用Popgene32和phylip软件进行数据计算和聚类分析。序列分析表明土生空团菌rDNA ITS区的序列长度为422–447bp,遗传距离在0.000–0.051之间。居群结构和聚类分析结果表明:(1)土生空团菌有一定的遗传多样性,且遗传差异主要来自于居群内;(2)基因流Nm>1,遗传漂变不是导致土生空团菌居群遗传分化的主要因素;(3)土生空团菌的遗传分化受到地理环境的影响,而与宿主来源没有明显相关性。     

链格孢菌毒素对紫茎泽兰的致病机理

以叶圆片法分析链格孢菌[Alternaria alternata(Fr.)Keissler]毒素对紫茎泽兰（Eupatorium adenophorum Spreng.)叶组织细胞膜透性、过氧化物酶（POD）、抗坏血酸过氧化物酶（APX）和过氧化氢酶（CAT）活性以及丙二醛（MDA）含量的影响,结果表明,链格孢菌毒素使紫茎泽兰叶组织细胞膜透性上升,Na^ 和K^ 渗漏量增加,膜脂过氧化加强,MDA含量上升;链格孢菌毒素处理的紫茎泽兰叶片中POD、APX和CAT的活性均较对照降低。     

Salinomycin induces apoptosis and senescence in breast cancer: Upregulation of p21, downregulation of survivin and histone H3 and H4 hyperacetylation

Background

In the present study, we investigated the effect of Salinomycin on the survival of three human breast cancer cell lines MCF-7, T47D and MDA-MB-231 grown in adherent culture conditions.

Methods

Cell viability was measured by CellTiter-Glo and Trypan blue exclusion assay. Apoptosis was determined by caspase 3/7 activation, PARP cleavage and Annexin V staining. Cell cycle distribution was assessed by propidium iodide flow cytometry. Senescence was confirmed by measuring the senescence-associated β-galactosidase activity. Changes in protein expression and histone hyperacetylation was determined by western blot and confirmed by immunofluorescence assay.

Results

Salinomycinwas able to inhibit the growth of the three cell lines in time- and concentration-dependent manners. We showed that depending on the concentrations used, Salinomycin elicits different effects on theMDA-MB-231 cells. High concentrations of Salinomycin induced a G2 arrest, downregulation of survivin and triggered apoptosis. Interestingly, treatment with low concentrations of Salinomycin induced a transient G1 arrest at earlier time point and G2 arrest at later point and senescence associatedwith enlarged cellmorphology, upregulation of p21 protein, increase in histone H3 and H4 hyperacetylation and expression of SA-β-Gal activity. Furthermore, we found that Salinomycin was able to potentiate the killing of the MCF-7 and MDA-MB-231 cells, by the chemotherapeutic agents, 4-Hydroxytamoxifen and frondoside A, respectively.

Conclusion

Our data are the first to link senescence and histone modifications to Salinomycin.

Significance

This study provides a new insight to better understand the mechanism of action of Salinomycin, at least in breast cancer cells.     

Mechanisms of the Anticancer Action of Ganoderma lucidum (Leyss. ex Fr.) Karst.: A New Understanding

Ganoderma lucidum (Leyss. ex Fr.) Karst., a medicinal fungus called "Lingzhi" in China, has been used in traditional Chinese medicine in China for the prevention and treatment of various types of diseases, such as cancer, hepatopathy, arthritis, hypertension, neurasthenia, and chronic hepatitis. It is clear that the anticancer activity of G. lucidum is mainly due to polysaccharides and/or triterpenoids of the fungus. However, until now, the mechanism of the anticancer action of G. lucidum has not been well understood and, previously, the activation of the immune response of the host was widely considered to be the only mechanism by which G. lucidum prevented and/or treated cancer. However, recent studies reviewed in the present paper have shown that the potential mechanisms of anticancer action include not only the activation of the immune response of the host, but also the induction of cell differentiation, the induction of Phase Ⅱ-metabolizing enzymes, the inhibition of angiogenesis, and the inhibition of the expression of the urokinase-type plasminogen activator (uPA) and the uPA receptor in cancer cells. To further elucidate the mechanisms of action of G. lucidum, more in vivo tests and randomized controlled clinical trials should be carried out, and the molecular mechanisms should be studied intensively. Additionally, whether the anticancer compounds in G. lucidum act synergistically or independently should be further studied.     

Structure and function of the ectomycorrhizal association between Paxillus involutus and Betula pendula. II. Metabolic changes during mycorrhiza formation

Seedlings of Betula pendula Roth. were grown in the presence of Paxillus involutus (Batsch) Fr., and metabolic changes during mycorrhiza formation were examined by measuring organic acid and amino acid pools and related enzyme activities, following sequential harvests. Glutamine, aspartate and asparagine pools were always lower in infected roots than in non-infected roots, especially during Hartig net initiation and formation. Glutamate concentration was similar in both tissues. Citrate and malate were the two major organic acids detected and their concentrations were equal in infected and non-infected roots. Aspartate aminotransferase, glutamine synthetase, NAD-dependent malate dehydrogenase and glucose-6-phosphate dehydrogenase activities were higher in infected roots than non-infected roots. For all enzymes revealed on polyacrylamide gels, both root and fungal isoforms were present in infected roots. Quantitative changes in enzyme capacities and metabolite pools indicated that mycorrhiza formation caused a re-arrangement of the main metabolic pathways during the very early stages following contact, which might be related to the structural changes.