Molecular cloning of homologs of RAS and RHO1 genes from Cryptococcus neoformans

Tanaka, Kenichi; Nambu, Hirohide; Katoh, Yoshiharu; Kai, Mayumi; Hidaka, Yoshiki

doi:10.1002/(sici)1097-0061(199908)15:11<1133::aid-yea438>3.3.co;2-e

Cited by 8 publications

(10 citation statements)

References 25 publications

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“…However, the induction of capsule around the cell does not appear to be due solely to the induction of the various biosynthetic genes. The next sections discuss the signaling pathways that regulate capsule and the transcriptional outputs that result in capsule induction (see Table S2 in the supplemental material) (44,119,194). …”

Section: Regulation Of Capsule Induction In Specific Environmentsmentioning

confidence: 99%

The Cryptococcus neoformans Capsule: a Sword and a Shield

2012

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SUMMARY The human fungal pathogen Cryptococcus neoformans is characterized by its ability to induce a distinct polysaccharide capsule in response to a number of host-specific environmental stimuli. The induction of capsule is a complex biological process encompassing regulation at multiple steps, including the biosynthesis, transport, and maintenance of the polysaccharide at the cell surface. By precisely regulating the composition of its cell surface and secreted polysaccharides, C. neoformans has developed intricate ways to establish chronic infection and dormancy in the human host. The plasticity of the capsule structure in response to various host conditions also underscores the complex relationship between host and parasite. Much of this precise regulation of capsule is achieved through the transcriptional responses of multiple conserved signaling pathways that have been coopted to regulate this C. neoformans -specific virulence-associated phenotype. This review focuses on specific host stimuli that trigger the activation of the signal transduction cascades and on the downstream transcriptional responses that are required for robust encapsulation around the cell.

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Section: Regulation Of Capsule Induction In Specific Environmentsmentioning

confidence: 99%

The Cryptococcus neoformans Capsule: a Sword and a Shield

2012

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“…The NC-ras2 gene of Neurospora crassa regulates hyphal growth, cell wall synthesis, and the formation of conidia (25). In Cryptococcus neoformans, RAS1 is required for growth at elevated temperatures, mating, filamentation, agar invasion, and sporulation (1,49). The Schizosaccharomyces pombe ras1 gene is involved in pheromone response, morphogenesis, and sporulation (16,57).…”

Section: Vol 1 2002mentioning

confidence: 99%

ras2 Controls Morphogenesis, Pheromone Response, and Pathogenicity in the Fungal Pathogen Ustilago maydis

2002

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Ustilago maydis, a pathogen of maize, is a useful model for the analysis of mating, pathogenicity, and the morphological transition between budding and filamentous growth in fungi. As in other fungi, these processes are regulated by conserved signaling mechanisms, including the cyclic AMP (cAMP)/protein kinase A (PKA) pathway and at least one mitogen-activated protein kinase (MAP kinase) pathway. A current challenge is to identify additional factors that lie downstream of the cAMP pathway and that influence morphogenesis in U. maydis. In this study, we identified suppressor mutations that restored budding growth to a constitutively filamentous mutant with a defect in the gene encoding a catalytic subunit of PKA. Complementation of one suppressor mutation unexpectedly identified the ras2 gene, which is predicted to encode a member of the well-conserved ras family of small GTP-binding proteins. Deletion of the ras2 gene in haploid cells altered cell morphology, eliminated pathogenicity on maize seedlings, and revealed a role in the production of aerial hyphae during mating. We also used an activated ras2 allele to demonstrate that Ras2 promotes pseudohyphal growth via a MAP kinase cascade involving the MAP kinase kinase Fuz7 and the MAP kinase Ubc3. Overall, our results reveal an additional level of crosstalk between the cAMP signaling pathway and a MAP kinase pathway influenced by Ras2.Many fungi are capable of alternating between budding and filamentous growth (dimorphism), and competence for this morphological switch can be an important factor in the virulence of several fungal pathogens of plants and animals (19,33,34). Morphological transitions are involved in the formation of three cell types in the maize pathogen Ustilago maydis, including budding haploid cells, filamentous dikaryons, and diploid teliospores. Haploid cells grow saprophytically and can participate in mating interactions when compatible partners exchange pheromone signals and form the conjugation tubes required for cell fusion. The product of fusion is an infectious dikaryotic cell type that proliferates with a filamentous morphology in host tissue and eventually forms melanized teliospores within tumors of the maize plant. Haploid cells are then produced meiotically following teliospore germination. Pigmented, asexual spores (chlamydospores) that form in response to nutritional deprivation have been reported for U. maydis but are less well characterized (30).Two unlinked mating type loci designated a and b play a major role in regulating dimorphism in U. maydis. A successful mating interaction is observed only when two cells have different specificities at both the a and b loci. The a locus encodes a pheromone (mfa1 or mfa2) and pheromone receptor (pra1 or pra2) and is responsible for cell recognition and cell fusion (6). The b locus encodes two homeodomain proteins, bE and bW, which are responsible for maintenance of the infectious dikaryon and completion of the life cycle (24,28,48). Pheromone response is regulated through a mitogen-activa...

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“…This result suggested that a cloned cDNA of C. neoformans could functionally suppress the temperature-sensitive mutation rho1-104 in S. cerevisiae. The sequence of the cloned C. neoformans cDNA insert showed great similarity to the RHO1 gene of S. cerevisiae and was almost identical to the published sequence of CnRHO1 cDNA of C. neoformans, which was obtained by PCR amplification (35). The differences between the cloned cDNA and the published CnRHO1 cDNA sequence were at positions 266 (T3C) and 500 (G3C) (35).…”

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confidence: 55%

“…The regulatory subunit is encoded by RHO1 (10,27,32). Recently, sequence analysis of the Cryptococcus neoformans RHO1 cDNA (CnRHO1) indicated that the putative protein encoded by CnRHO1 contains 197 amino acids and shares a high degree of sequence identity with Rho1p in other fungal species (35). The function of CnRHO1 in C. neoformans, however, was not elucidated.…”

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confidence: 99%