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Query: UNIPROT:P06889 (Mol)
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Cryptococcus neoformans is an opportunistic pathogen responsible for serious disease in humans. Critical for virulence of this fungus is an elaborate polysaccharide capsule, which impedes the host immune response. We found that association of the capsule with the cell requires a specific component of the cell wall, alpha-1,3-glucan. Post-transcriptional inhibition of alpha-1,3-glucan synthase expression, using double-stranded RNA interference, yields cells that are unable to assemble a capsule although they generate its polysaccharide components. The resulting cryptococci are slow-growing and acapsular. This finding demonstrates a novel mode of polysaccharide attachment and an important application of RNA interference in fungi. The elimination of the capsule by reducing the expression of a single gene suggests a potential avenue for antifungal chemotherapy.
Mol Microbiol 2003 Nov
PMID:Cell wall alpha-1,3-glucan is required to anchor the Cryptococcus neoformans capsule. 1462 25

Paracoccidioides brasiliensis, a thermodimorphic fungus, is the causative agent of paracoccidioidomycosis (PCM), the most prevalent systemic mycosis in Latin America. Pathogenicity appears to be intimately related to the dimorphic transition from the hyphal to the yeast form, which is induced by a shift from environmental temperature to the temperature of the mammalian host. Little information is available on the P. brasiliensis genes that are necessary during the pathogenic phase. We have therefore undertaken Suppression Subtraction Hybridization (SSH) and macroarray analyses with the aim of identifying genes that are preferentially expressed in the yeast phase. Genes identified by both procedures as being more highly expressed in the yeast phase are involved in basic metabolism, signal transduction, growth and morphogenesis, and sulfur metabolism. In order to test whether the observed changes in gene expression reflect the differences between the growth conditions used to obtain the two morphological forms rather than differences intrinsic to the cell types, we performed real-time RT-PCR experiments using RNAs derived from both yeast cells and mycelia that had been cultured at 37 degrees C and 26 degrees C in either complete medium (YPD or Sabouraud) or minimal medium. Twenty genes, including AGS1 (alpha-1,3-glucan synthase) and TSA1 (thiol-specific antioxidant), were shown to be more highly expressed in the yeast cells than in the hyphae. Although their levels of expression could be different in rich and minimal media, there was a general tendency for these genes to be more highly expressed in the yeast cells.
Mol Genet Genomics 2004 Jul
PMID:Identification of genes preferentially expressed in the pathogenic yeast phase of Paracoccidioides brasiliensis, using suppression subtraction hybridization and differential macroarray analysis. 1513 90

In Aspergillus niger, the genes coding for glutamine:fructose-6-phosphate amidotransferase (gfaA) and alpha-1,3-glucan synthase (agsA) are induced in response to cell wall stress. In silico analysis of the promoter region of the two genes revealed the presence of putative DNA binding sites for transcription factors involved in stress responses, including sites identical to the Saccharomyces cerevisiae Rlm1p and Msn2p/Msn4p transcription factors. Promoter analysis indicated that the induction of the agsA gene in response to cell wall stress is fully dependent on a putative Rlm1p binding site in its promoter region. Database searches revealed the presence of S. cerevisiae Rlm1p homologues in most filamentous fungi examined, including A. niger. Deletion of the RLM1 homologue, named rlmA in A. niger, completely eliminated the induction of agsA and resulted in a twofold reduced induction of gfaA during Calcofluor White-induced cell wall stress. The rise in cell wall chitin in the presence of Calcofluor White was also affected in the rlmA deletion strain. In addition, the deletion strain was more sensitive towards cell wall stress agents. Our results indicate that A. niger responds to cell wall stress by transcriptional activation of cell wall reinforcing genes including agsA and gfaA through an Rlm1p-like transcription factor. We propose that such a cell wall salvage mechanism is wide spread in filamentous fungi.
Mol Microbiol 2005 Oct
PMID:The Aspergillus niger MADS-box transcription factor RlmA is required for cell wall reinforcement in response to cell wall stress. 1616 67