Inositol biosynthesis: Candida albicans and Saccharomyces cerevisiae genes share common regulation

Abstract

The Candida albicans inositol biosynthetic gene and its regulation have been studied. The gene, CalNO1, was cloned on a multicopy vector by complementation of a Saccharomyces cerevisae mutant strain. Southern blot analysis established that the cloned DNA was C. albicans genomic DNA in origin; neither rearrangements nor pseudogenes were evident. Blot hybridization analysis using RNA isolated from C. albicans revealed that a single RNA species (1.8 kilobases) was homologous to the cloned DNA fragment. The steady-state levels of these transcripts were shown to be regulated in response to inositol in the growth media. In addition, the steady-state levels of the RNA encoded by the cloned C. albicans DNA present in S. cerevisiae on a plasmid (YRpCalNO1) were regulated in response to exogenously provided inositol. The cloned C. albicans DNA fragment was shown to restore inositol-1-phosphate synthase activity to a S. cerevisiae mutant strain defective in this enzyme. This activity was also shown to be regulated in response to the presence of inositol in the growth media.

Function of Phosphatidylinositol in Mycobacteria

“…Both pHBJ378 and the vector pHBJ334 were introduced into M. smegmatis mc 2 155 wild type and ino1 mutant strains by electrotransformation (19). IPS Enzyme Assay-The IPS activity was assayed essentially as described previously (24), except that the inositol and glucose in the samples were detected by aluminum-backed Silica Gel 60 high performance thin layer chromatography (HPTLC) sheets (Merck). The HPTLC was developed three times in 1-propanol:acetone:water (9:6:5, 5:4:1, and 9:6:5, v/v), and then the amount of inositol and glucose was measured on a HPTLC plate reader (Berthold 2 , and lipids were separated from salts and polar metabolites by biphasic partitioning in 1-butanol:water (2:1, v/v).…”

Ribosomal protein genes in the yeast Candida albicans may be activated by a heterodimeric transcription factor related to Ino2 and Ino4 from S. cerevisiae

“…The availability of its complete genomic sequence (Jones et al 2004;Braun et al 2005) allows the identiWcation of putative orthologues to genes of S. cerevisiae and a subsequent functional comparison. Indeed, CaINO1 was able to complement an ino1 mutant of S. cerevisiae (Klig et al 1991) and CaOPI1 encoding a protein distantly related to Opi1 repressor could restore IC regulation after expression in a S. cerevisiae opi1 mutant . We thus expected that the genome of C. albicans should also encode proteins related to bHLH regulators Ino2 and Ino4.…”

“…Similar to S. cerevisiae, the dimorphic yeast Candida albicans contains genes CaFAS1, CaFAS2, CaINO1 and CaCHO1 (Klig et al 1991;Zhao and Cihlar 1994;Southard and Cihlar 1995) and is able to synthesize fatty acids, inositol and choline de novo. Since C. albicans may become pathogenic in immunosuppressed patients, this diploid (and partially aneuploid) yeast is considered as a model system for fungal infections (Berman and Sudbery 2002;Selmecki et al 2005).…”

High-affinity myo-inositol transport in Candida albicans: substrate specificity and pharmacology

“…Interestingly, the subsequent enzyme in inositol biosynthesis, inositol monophosphatase INM1 (Murray & Greenberg, 2000), which dephosphorylates myo-inositol 1-phosphate to myo-inositol, is still functional in Schizosaccharomyces pombe (Ingavale & Bachhawat, 1999). While an INO1 gene homologue has been identified in C. albicans (Klig et al, 1991), the complete biosynthetic pathway and a functional inositol monophosphatase have not been described in Candida. Hence, either synthesis or transport of myo-inositol (or both) is essential for yeast viability.…”