We have characterized CaNrg1 from Candida albicans, the major fungal pathogen in humans. CaNrg1 contains a zinc finger domain that is conserved in transcriptional regulators from fungi to humans. It is most closely related to ScNrg1, which represses transcription in a Tup1‐dependent fashion in Saccharomyces cerevisiae. Inactivation of CaNrg1 in C.albicans causes filamentous and invasive growth, derepresses hypha‐specific genes, increases sensitivity to some stresses and attenuates virulence. A tup1 mutant displays similar phenotypes. However, unlike tup1 cells, nrg1 cells can form normal hyphae, generate chlamydospores at normal rates and grow at 42°C. Transcript profiling of 2002 C.albicans genes reveals that CaNrg1 represses a subset of CaTup1‐regulated genes, which includes known hypha‐specific genes and other virulence factors. Most of these genes contain an Nrg1 response element (NRE) in their promoter. CaNrg1 interacts specifically with an NRE in vitro. Also, deletion of two NREs from the ALS8 promoter releases it from Nrg1‐mediated repression. Hence, CaNrg1 is a transcriptional repressor that appears to target CaTup1 to a distinct set of virulence‐related functions, including yeast–hypha morphogenesis.

We present an experimental and computational pipeline for the generation of kinetic models of metabolism, and demonstrate its application to glycolysis in Saccharomyces cerevisiae. Starting from an approximate mathematical model, we employ a “cycle of knowledge” strategy, identifying the steps with most control over flux. Kinetic parameters of the individual isoenzymes within these steps are measured experimentally under a standardised set of conditions. Experimental strategies are applied to establish a set of in vivo concentrations for isoenzymes and metabolites. The data are integrated into a mathematical model that is used to predict a new set of metabolite concentrations and reevaluate the control properties of the system. This bottom-up modelling study reveals that control over the metabolic network most directly involved in yeast glycolysis is more widely distributed than previously thought.

Candida albicans expresses specific virulence traits that promote disease establishment and progression. These traits include morphological transitions between yeast and hyphal growth forms that are thought to contribute to dissemination and invasion and cell surface adhesins that promote attachment to the host. Here, we describe the regulation of the adhesin gene ALS3, which is expressed specifically during hyphal development in C. albicans. Using a combination of reporter constructs and regulatory mutants, we show that this regulation is mediated by multiple factors at the transcriptional level. The analysis of ALS3 promoter deletions revealed that this promoter contains two activation regions: one is essential for activation during hyphal development, while the second increases the amplitude of this activation. Further deletion analyses using the Renilla reniformis luciferase reporter delineate the essential activation region between positions ؊471 and ؊321 of the promoter. Further 5 or 3 deletions block activation. ALS3 transcription is repressed mainly by Nrg1 and Tup1, but Rfg1 contributes to this repression. Efg1, Tec1, and Bcr1 are essential for the transcriptional activation of ALS3, with Tec1 mediating its effects indirectly through Bcr1 rather than through the putative Tec1 sites in the ALS3 promoter. ALS3 transcription is not affected by Cph2, but Cph1 contributes to full ALS3 activation. The data suggest that multiple morphogenetic signaling pathways operate through the promoter of this adhesin gene to mediate its developmental regulation in this major fungal pathogen.Candida albicans is a major opportunistic pathogen of humans (54). This fungus is a frequent cause of superficial oral and vaginal infections, and in immunocompromised patients, C. albicans can disseminate via the bloodstream to invade internal organs, thereby causing deep-seated, systemic infections that are often fatal (54).Various factors are thought to contribute to the virulence of C. albicans. These include adhesion to host tissue, the ability to undergo reversible morphogenetic transitions between budding (yeast) and filamentous (hyphae and pseudohyphae) growth forms, the secretion of extracellular hydrolases, and rapid switching between different phenotypic forms (30,42,44,65). The contribution of yeast-hypha morphogenesis to C. albicans virulence has been hotly debated (21,29,71). However, it is clear that hyphal development is closely associated with tissue invasion (21,61,71,83).Adherence plays a key role in fungal colonization (27,68,70). C. albicans expresses an array of adhesin genes including HWP1, which encodes a cell surface glycoprotein that acts as a target for mammalian transglutaminases. These enzymes are thought to generate covalent cross-links between Hwp1 on the fungal hyphal surface and proteins on the mammalian cell surface (68, 72). The ALS gene gamily encodes a set of differentially regulated cell surface glycosylphosphatidylinositol-anchored glycoproteins that promote fungal adherence (27,55). ALS3 was init...

Polymerase chain reaction amplification of the intergenic spacer region between the 5S and 18S genes from Meloidogyne chitwoodi, M. fallax, and M. hapla enabled these three important temperate species to be differentiated. Length polymorphism was found between M. chitwoodi and M. fallax as a result of differing numbers of short repeats located between the 5S and 18S genes. The presence of the 5S gene within the rDNA cistrons was confirmed in the Meloidogyne spp. included in this study. The region between the 28S and 5S genes for M. chitwoodi and M. fallax was short and lacked variability in repeated sequences compared with the main tropical Meloidogyne spp. and M. hapla. Differences in the number of these repeats resulted in intraspecific length polymorphism for M.hapla.