Synonymous and Nonsynonymous Substitutions in Dictyostelium discoideum Ammonium Transporter Are Necessary for Functional Complementation in Saccharomyces cerevisiae.

Ammonium transporters are present in all three domains of life. They have undergone extensive horizontal gene transfer (HGT), gene duplication, and functional diversification and therefore offer an excellent paradigm to study protein evolution. We attempted to complement a ΔΔΔ strain of Saccharomyces cerevisiae (triple-deletion strain), which otherwise cannot grow on ammonium as a sole nitrogen source at concentrations of <3 mM, with of Dictyostelium discoideum, an orthologue of S.

KRH1 and KRH2 are functionally non-redundant in signaling for pseudohyphal differentiation in Saccharomyces cerevisiae.

Diploid cells of Saccharomyces cerevisiae undergo pseudohyphal differentiation in response to nutrient depletion. Although this dimorphic transition occurs due to signals originating from carbon and nitrogen limitation, how these signals are coordinated and integrated is not understood. Results of this study indicate that the pseudohyphal defect of the mep2∆ mutant is overcome upon disruption of KRH2/GPB1 but not KRH1/GPB2.

Epigenetics of the yeast galactose genetic switch.

The transcriptional activation of enzymes involved in galactose utilization (GAL genes) in Saccharomyces cerevisiae is regulated by a complex interplay between three regulatory proteins encoded by GAL4 (transcriptional activator), GAL3 (signal transducer) and GAL80 (repressor). The relative concentrations of the signal transducer and the repressor are maintained by autoregulation. Cells disabled for autoregulation exhibit phenotypes distinctly different from that of the wild type cells, enabling us to explore the biological significance of autoregulation.

Pseudohyphal differentiation defect due to mutations in GPCR and ammonium signaling is suppressed by low glucose concentration: a possible integrated role for carbon and nitrogen limitation.

In response to carbon and/or nitrogen limitation, diploid cells of Saccharomyces cerevisiae either sporulate or develop pseudohyphae. Although the signal transduction pathways leading to these developmental changes have been extensively studied, how nutritional signals are integrated is not clearly understood. Results of this study indicate that reducing glucose concentration from 2% (SLAD) to 0.

Cryptococcal meningitis in AIDS.

A study was carried out to determine the incidence of Cryptococcus species in AIDS patients and their susceptibility pattern to the different antifungal drugs used for therapy. PCR as a rapid diagnostic tool for cryptococcal meningitis was evaluated. All the isolates were senstive to the three antifungal drugs tested indicating that the development of drug resistance is not a major problem in the treatment of cryptococcosis.