Establishment of a new cross of the rice blast fungus derived from Japanese differential strain Ina168 and hermaphroditic rice pathogen Guy11. (1/1263)

Mating experiments between Magnaporthe grisea Japanese rice pathogens and Guy11, a hermaphroditic fertile rice pathogen, were done aimed at identification of avirulence genes. A cross named cross 2107 with thirty-six random progenies was obtained. Segregation analyses of genetic markers found that the cross was less suitable for genetic analysis. Backcrosses with cross 2107 progenies and Guy11 were done and another cross named cross 5307 with sixty-five progenies was obtained. A locus controlling kasugamycin resistance named Ksg1R was identified and used for a model case of genetic mapping. Bulked segregant analysis was done to find adjacent RAPD markers for mapping of the gene. Three adjacent markers to Ksg1R were obtained and a genetic map around the Ksg1R was made, but these markers were not located on a single chromosome. These results suggest that genetic analysis to identify a gene locus is available in cross 5307. Infection assay of parental strains of cross 5307 to Japanese differential rice cultivars suggested the possibility of genetic analysis of cultivar specificity toward four rice cultivars: Aichi-asahi, Kusabue, Tsuyuake, and K59.  (+info)

Improved properties of baker's yeast mutants resistant to 2-deoxy-D-glucose. (2/1263)

We isolated spontaneous mutants from Saccharomyces cerevisiae (baker's yeast V1) that were resistant to 2-deoxy-D-glucose and had improved fermentative capacity on sweet doughs. Three mutants could grow at the same rate as the wild type in minimal SD medium (0.17% Difco yeast nitrogen base without amino acids and ammonium sulfate, 0.5% ammonium sulfate, 2% glucose) and had stable elevated levels of maltase and/or invertase under repression conditions but lower levels in maltose-supplemented media. Two of the mutants also had high levels of phosphatase active on 2-deoxy-D-glucose-6-phosphate. Dough fermentation (CO2 liberation) by two of the mutants was faster and/or produced higher final volumes than that by the wild type, both under laboratory and industrial conditions, when the doughs were supplemented with glucose or sucrose. However, the three mutants were slower when fermenting plain doughs. Fermented sweet bakery products obtained with these mutants were of better quality than those produced by the wild type, with regard to their texture and their organoleptic properties.  (+info)

Evolution of antifungal susceptibility among Candida species isolates recovered from human immunodeficiency virus-infected women receiving fluconazole prophylaxis. (3/1263)

The effect of fluconazole on the susceptibility of Candida isolates recovered from women infected with human immunodeficiency virus (HIV) was evaluated in a randomized, double-blind, placebo-controlled trial. Women with CD4(+) cell counts of < or =300 cells/mm(3) received either fluconazole (200 mg/week) or placebo as prophylaxis. The antifungal susceptibility of specimens was evaluated. One patient who received fluconazole and 2 patients assigned to placebo had Candida albicans isolates recovered that were resistant to fluconazole (MIC, > or =64 microg/mL). Eleven patients assigned fluconazole and 4 patients assigned placebo had non-albicans Candida strains (all Candida glabrata) recovered that were resistant to fluconazole. There was significant azole cross-resistance among the non-albicans Candida species isolates. Although the rate of azole resistance did not significantly increase after fluconazole prophylaxis, there was a trend toward more in vitro azole resistance in C. glabrata isolates from patients assigned fluconazole. Moreover, the majority of resistant vaginal isolates of Candida species were recovered after initiation of open-label fluconazole use.  (+info)

Antioxidant functions required for insusceptibility of Saccharomyces cerevisiae to tetracycline antibiotics. (4/1263)

Cu,Zn superoxide dismutase (Sod1) is required for insusceptibility of Saccharomyces cerevisiae to oxytetracycline (OTC). Here we report that Sod1 is also required for insusceptibility to doxycycline (DOX). Furthermore, among a range of antioxidant and redox balance mutants, mac1 and ctr1 deletion strains exhibited marked sensitization to OTC and DOX. Certain mutants exhibited a slight sensitivity to methacycline and minocycline. Addition of copper suppressed antibiotic sensitivity. Thus, intracellular copper as well as superoxide dismutase can be critical for eukaryotic tolerance of several tetracycline antibiotics.  (+info)

Emergence of resistance to fluconazole as a cause of failure during treatment of histoplasmosis in patients with acquired immunodeficiency disease syndrome. (5/1263)

In sequential clinical trials of treatment for histoplasmosis in patients with acquired immunodeficiency syndrome, therapy with fluconazole failed in a higher proportion of patients than did therapy with itraconazole. To determine the cause for failure with fluconazole, antifungal susceptibility testing that used modified National Committee on Clinical Laboratory Standards procedures was performed on all baseline and failure isolates. Failure occurred more frequently in patients with baseline isolates with fluconazole minimum inhibitory concentrations (MICs) > or =5 microg/mL versus lower MICs; 29% versus 3%, respectively. There was at least a 4-fold increase in fluconazole MIC in the isolates from 10 (59%) of 17 patients for whom paired pretreatment and failure or relapse isolates were available. Cross-resistance to itraconazole was not seen. In conclusion, fluconazole is less active than itraconazole for Histoplasma capsulatum and induces resistance during therapy, which accounted for treatment failure in some patients.  (+info)

The target of rapamycin signaling pathway regulates mRNA turnover in the yeast Saccharomyces cerevisiae. (6/1263)

The target of rapamycin (TOR) signaling pathway is an important mechanism by which cell growth is regulated by nutrient availability in eukaryotes. We provide evidence that the TOR signaling pathway controls mRNA turnover in Saccharomyces cerevisiae. During nutrient limitation (diauxic shift) or after treatment with rapamycin (a specific inhibitor of TOR), multiple mRNAs were destabilized, whereas the decay of other mRNAs was unaffected. Our findings suggest that the regulation of mRNA decay by the TOR pathway may play a significant role in controlling gene expression in response to nutrient depletion. The inhibition of the TOR pathway accelerated the major mRNA decay mechanism in yeast, the deadenylation-dependent decapping pathway. Of the destabilized mRNAs, two different responses to rapamycin were observed. Some mRNAs were destabilized rapidly, while others were affected only after prolonged exposure. Our data suggest that the mRNAs that respond rapidly are destabilized because they have short poly(A) tails prematurely either as a result of rapid deadenylation or reduced polyadenylation. In contrast, the mRNAs that respond slowly are destabilized by rapid decapping. In summary, the control of mRNA turnover by the TOR pathway is complex in that it specifically regulates the decay of some mRNAs and not others and that it appears to control decay by multiple mechanisms.  (+info)

The role of PDR13 in tolerance to high copper stress in budding yeast. (7/1263)

PDR13 in Saccharomyces cerevisiae contributes to drug resistance via sequential activation of PDR1 and PDR5. In this study, we found that a PDR13 deletion mutant was hypersensitive to Cu(2+) compared to the wild-type counterpart. The Cu(2+) tolerance mechanism mediated by Pdr13 does not seem to involve Pdr1 or Pdr5, since mutants harboring a deletion of either the PDR1 or PDR5 gene did not show elevated Cu(2+) sensitivity. Instead, we found that the PDR13 null mutant could not express CUP1 or CRS5 metallothionein at wild-type levels when subjected to high Cu(2+) stress. These results suggest that Pdr13 contributes to high Cu(2+) tolerance of S. cerevisiae, at least in part, via a mechanism involving metallothionein expression.  (+info)

Phosphorylation of gamma-tubulin regulates microtubule organization in budding yeast. (8/1263)

gamma-Tubulin is essential for microtubule nucleation in yeast and other organisms; whether this protein is regulated in vivo has not been explored. We show that the budding yeast gamma-tubulin (Tub4p) is phosphorylated in vivo. Hyperphosphorylated Tub4p isoforms are restricted to G1. A conserved tyrosine near the carboxy terminus (Tyr445) is required for phosphorylation in vivo. A point mutation, Tyr445 to Asp, causes cells to arrest prior to anaphase. The frequency of new microtubules appearing in the SPB region and the number of microtubules are increased in tub4-Y445D cells, suggesting this mutation promotes microtubule assembly. These data suggest that modification of gamma-tubulin is important for controlling microtubule number, thereby influencing microtubule organization and function during the yeast cell cycle.  (+info)