Crg, a gene required for Ur-3-mediated rust resistance in common bean, maps to a resistance gene analog cluster.
(49/1530)
Race-specific resistance to the bean rust pathogen (Uromyces appendiculatus) is provided by a number of loci in common bean (Phaseolus vulgaris). The Ur-3 locus controls hypersensitive resistance (HR) to 44 of the 89 races curated in the United States. To better understand resistance mediated by this locus, we developed new genetic material for analysis. We developed a population of mutagenized seed of cv. Sierra (genotype = Ur-3 ur-4 ur-6) that was screened with a bean rust race that is normally incompatible (HR response) on Ur-3 genotypes. We discovered two mutants of common bean, crg and ur3-delta3, in which uredinia formed on leaves (a compatible interaction) following infection. The F1 generation from a cross of these two mutants expressed the HR response, and the F2 generation segregated in a ratio of 9:7 (HR/uredinia formation). Therefore, the two genes are unlinked. Further genetic analysis determined that the mutation in ur3-delta3 was in the Ur-3 locus, and the mutation in crg was in a newly discovered gene given the symbol Crg (Complements resistance gene). Each mutation was inherited in a recessive manner. Unlike ur3-delta3, crg expressed reduced compatibility to bean rust races 49 and 47 that are normally fully compatible on genotypes, such as Sierra, that are homozygous recessive at the Ur-4 and Ur-6 loci. This suggests a gene mutated in crg is normally a positive compatibility factor for the bean-bean rust interaction. Polymerase chain reaction analysis of crg with primers to common bean resistance gene analogs (RGA) that contain a nucleotide-binding site sequence similar to those found in a number of plant disease resistance genes revealed that crg is missing the SB1 RGA, but not the linked SB3 and SB5 RGAs. Genetic analyses revealed that Crg cosegregates with the SB1 RGA. These results demonstrate that Crg is located near a RGA cluster in the common bean genome. (+info)
Growth potential of Clostridium botulinum in fresh mushrooms packaged in semipermeable plastic film.
(50/1530)
Fresh mushrooms (Agaricus bisporus) were inoculated in the stem, gill, or cap with Clostridium botulinum spores. They were placed with uninoculated mushrooms in paper board trays, which were then covered and sealed in a polyvinyl chloride stretch film to simulate prepackaged mushrooms available at retail stores. When incubated at 20 C, botulinum toxin could be detected as early as day 3, or 4, when the mushrooms still appear edible. Mushrooms inoculated in the stem with 1,000 type A spores frequently became botulinogenic; higher spore levels were needed if gills or caps were inoculation sites. Type B spores were less apt to produce toxic mushrooms. Respiration of the fresh mushrooms used up O2 more rapidly than could enter through the semipermeable wrapping film, so that the equilibrium O2 concentration became low enough for growth of C. botulinum. Inoculated mushrooms did not become botulinogenic when held at 4 C. (+info)
Phellinsin A, a novel chitin synthases inhibitor produced by Phellinus sp. PL3.
(51/1530)
Phellinsin A, a novel chitin synthases inhibitor was isolated from the cultured broth of fungus PL3, which was identified as Phellinus sp. PL3. Phellinsin A was purified by solvent partition, silica gel, ODS column chromatographies, and preparative HPLC, consecutively. The structure of phellinsin A was assigned as a phenolic compound on the basis of various spectroscopic analyses including UV, IR, Mass, and NMR. Its molecular weight and formula were found to be 358 and C18H14O8, respectively. Phellinsin A selectively inhibited chitin synthase I and II of Saccharomyces cerevisiae with an IC50 value of 76 and 28 microg/ml, respectively, in our cell free assay system. This compound showed antifungal activity against Colletotrichum lagenarium, Pyricularia oryzae, Rhizoctonia solani, Aspergillus fumigatus, and Trichophyton mentagrophytes. (+info)
The effect of cytochalasin B on hyphal morphogenesis in Polyporus biennis.
(52/1530)
Cytochalasin B inhibited the radial growth rate of Polyporus biennis, and caused an increase in hyphal density through a reduction in the distance between successive branches. Cytochalasin B also produced irregular hyphal profiles and, in a small percentage of hyphae, forked apices. The position of clamp connexions was little affected by cytochalasin B, but the developmental process was specifically inhibited during initiation and during the last two stages, when contact and dissolution of the clamp were occurring. There were no major disruptions of the ultrastructure of the dolipore/parenthesome septum caused by cytochalasin B treatment. (+info)
The irpexans, a new group of biologically active metabolites produced by the basidiomycete Irpex sp. 93028.
(53/1530)
Five novel antibiotics described as irpexans (1, 2, 3a, 3b, 4) were isolated from fermentations of an Irpex species in the course of a screening for new inhibitors of AP-1 and NF-kappaB mediated signal transduction pathways in COS-7 cells using secreted alkaline phosphatase (SEAP) as a reporter gene. The expression of an AP-1 and NF-kappaB driven SEAP reporter gene was inhibited in a dose dependent manner with 14-acetoxy-15-hydroxyirpexan (3b) being the most potent compound, followed by 14,15-irpexanoxide (2), 14,15-dihydroxyirpexan (3a) and 14-acetoxy-22,23-dihydro-15,23-dihydroxyirpexan (4). Irpexan (1) exhibited no activity. The irpexans (1, 2, 3a, 3b, 4) are characterized by weak cytotoxic but neither antibacterial nor antifungal activities. All five compounds are terpenoids with a mannose moiety. The structures were elucidated by spectroscopic methods. (+info)
Effects of maitake (Grifola frondosa) polysaccharide on collagen-induced arthritis in mice.
(54/1530)
We recently reported the anti-hepatitis effect of a polysaccharide, designated as the D-fraction, extracted from maitake. Its effect includes immuno-regulating activities. We investigated the effect of the glucan in collagen-induced arthritis (CIA). The D-fraction was administered to CIA mice for 30 consecutive days. Arthritis development was observed from the 4th day after the second immunization. The D-fraction did not have any influence on anti-type II collagen antibodies in blood serum or activated B cells. To determine how cellular immunity may be involved in the development of CIA, ratios of CD4+ T cells and their activated form in the axillary and inguinal lymph node T cells were detected by flow cytometry analysis. The ratios were not different between the D-fraction group and the control group. However, interleukin-1beta, granulocyte-macrophage colony-stimulating factor and tumor necrosis factor-alpha productions from splenic macrophages were significantly increased to 2.0, 4.7 and 1.9 times the control group level, respectively. The ratio of macrophages in the whole spleen cells was 2.3 times that of the control group, and their migrating ability was 1.9 times higher. Based on these results, we concluded that the arthritis development induced by D-fraction administration is attributable to the activation of splenic macrophages. (+info)
In vitro activities of approved and investigational antifungal agents against 44 clinical isolates of basidiomycetous fungi.
(55/1530)
The in vitro activity of amphotericin B, fluconazole, flucytosine, itraconazole, voriconazole, and posaconazole was evaluated against 44 clinical isolates of filamentous basidiomycetous fungi. No statistically significant differences were noted between Schizophyllum commune (n = 5), Coprinus species (n = 8), Bjerkandera adusta (n = 14), and sterile, uncharacterized basidiomycetes (n = 17). (+info)
Two novel diterpenoids, erinacines H and I from the mycelia of Hericium erinaceum.
(56/1530)
Novel diterpenoids, erinacines H (1) and I (3), were isolated from the cultured mycelia of Hericium erinaceum. The structures of the compounds were determined by interpretation of the spectral data. Erinacine H showed stimulating activity of nerve growth factor (NGF)-synthesis. (+info)