This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Som, T Articles by Kolaparthi, V S Search for Related Content PubMed PubMed Citation Articles by Som, T Articles by Kolaparthi, V S

Developmental decisions in Aspergillus nidulans are modulated by Ras activity.

Department of Microbiology and Immunology, Jefferson Cancer Institute, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.

ABSTRACT

To better understand how Ras controls development of multicellular organisms, we have chosen Aspergillus nidulans as a model system. When grown on solid medium, this fungus follows a well-defined program of development, sequentially giving rise to several cell types which produce three distinct structures: vegetative hyphae, aerial hyphae, and the conidiophore structure. Here we describe a ras homolog found in this fungus (Aras) and demonstrate that it is an essential gene that regulates the ordered program of development. We created dominant alleles of this gene and expressed them to different levels in order to vary the ratio of GTP-bound (active) to GDP-bound (inactive) A-Ras protein. When the amount of active Ras is large, nuclear division proceeds, but further development is inhibited at the early step of germ tube formation. At an intermediate level of active Ras, aerial hypha formation is inhibited, while at a low level, conidiophore formation is inhibited. Maintenance of an even lower level of the active Ras is essential for initiation and progression of conidiophore formation, the final stage of development. When the level of active Ras is artificially lowered, each stage of development is initiated prematurely except germination, the initial stage of development. Therefore, the progression of the ordered developmental pathway of A. nidulans is dependent upon an initial high level of active Ras followed by its gradual decrease. We propose that several concentration threshold exist, each of which allows development to proceed to a certain point, producing the proper cell type while inhibiting further development.

This article has been cited by other articles:

• Harispe, L., Portela, C., Scazzocchio, C., Penalva, M. A., Gorfinkiel, L. (2008). Ras GTPase-Activating Protein Regulation of Actin Cytoskeleton and Hyphal Polarity in Aspergillus nidulans. Eukaryot Cell 7: 141-153 [Abstract] [Full Text]  
• Fortwendel, J. R., Zhao, W., Bhabhra, R., Park, S., Perlin, D. S., Askew, D. S., Rhodes, J. C. (2005). A Fungus-Specific Ras Homolog Contributes to the Hyphal Growth and Virulence of Aspergillus fumigatus. Eukaryot Cell 4: 1982-1989 [Abstract] [Full Text]  
• Lafon, A., Seo, J.-A., Han, K.-H., Yu, J.-H., d'Enfert, C. (2005). The Heterotrimeric G-Protein GanB({alpha})-SfaD({beta})-GpgA({gamma}) Is a Carbon Source Sensor Involved in Early cAMP-Dependent Germination in Aspergillus nidulans. Genetics 171: 71-80 [Abstract] [Full Text]  
• Leiter, E., Szappanos, H., Oberparleiter, C., Kaiserer, L., Csernoch, L., Pusztahelyi, T., Emri, T., Pocsi, I., Salvenmoser, W., Marx, F. (2005). Antifungal Protein PAF Severely Affects the Integrity of the Plasma Membrane of Aspergillus nidulans and Induces an Apoptosis-Like Phenotype. Antimicrob. Agents Chemother. 49: 2445-2453 [Abstract] [Full Text]  
• Chang, M.-H., Chae, K.-S., Han, D.-M., Jahng, K.-Y. (2004). The GanB G{alpha}-Protein Negatively Regulates Asexual Sporulation and Plays a Positive Role in Conidial Germination in Aspergillus nidulans. Genetics 167: 1305-1315 [Abstract] [Full Text]  
• Bok, J. W., Keller, N. P. (2004). LaeA, a Regulator of Secondary Metabolism in Aspergillus spp.. Eukaryot Cell 3: 527-535 [Abstract] [Full Text]  
• Shimizu, K., Hicks, J. K., Huang, T.-P., Keller, N. P. (2003). Pka, Ras and RGS Protein Interactions Regulate Activity of AflR, a Zn(II)2Cys6 Transcription Factor in Aspergillus nidulans. Genetics 165: 1095-1104 [Abstract] [Full Text]  
• Dou, X., Wu, D., An, W., Davies, J., Hashmi, S. B., Ukil, L., Osmani, S. A. (2003). The PHOA and PHOB Cyclin-Dependent Kinases Perform an Essential Function in Aspergillus nidulans. Genetics 165: 1105-1115 [Abstract] [Full Text]  
• Zuber, S., Hynes, M. J., Andrianopoulos, A. (2003). The G-Protein {alpha}-Subunit GasC Plays a Major Role in Germination in the Dimorphic Fungus Penicillium marneffei. Genetics 164: 487-499 [Abstract] [Full Text]  
• Calvo, A. M., Wilson, R. A., Bok, J. W., Keller, N. P. (2002). Relationship between Secondary Metabolism and Fungal Development. Microbiol. Mol. Biol. Rev. 66: 447-459 [Abstract] [Full Text]  
• Firon, A., Beauvais, A., Latge, J.-P., Couve, E., Grosjean-Cournoyer, M.-C., d'Enfert, C. (2002). Characterization of Essential Genes by Parasexual Genetics in the Human Fungal Pathogen Aspergillus fumigatus: Impact of Genomic Rearrangements Associated With Electroporation of DNA. Genetics 161: 1077-1087 [Abstract] [Full Text]  
• Ichinomiya, M., Motoyama, T., Fujiwara, M., Takagi, M., Horiuchi, H., Ohta, A. (2002). Repression of chsB expression reveals the functional importance of class IV chitin synthase gene chsD in hyphal growth and conidiation of Aspergillus nidulans. Microbiology 148: 1335-1347 [Abstract] [Full Text]  
• Memmott, S. D., Ha, Y.-s., Dickman, M. B. (2002). Proline Reverses the Abnormal Phenotypes of Colletotrichum trifolii Associated with Expression of Endogenous Constitutively Active Ras. Appl. Environ. Microbiol. 68: 1647-1651 [Abstract] [Full Text]  
• Boyce, K. J., Hynes, M. J., Andrianopoulos, A. (2001). The CDC42 Homolog of the Dimorphic Fungus Penicillium marneffei Is Required for Correct Cell Polarization during Growth but Not Development. J. Bacteriol. 183: 3447-3457 [Abstract] [Full Text]  
• Shimizu, K., Keller, N. P. (2001). Genetic Involvement of a cAMP-Dependent Protein Kinase in a G Protein Signaling Pathway Regulating Morphological and Chemical Transitions in Aspergillus nidulans. Genetics 157: 591-600 [Abstract] [Full Text]  
• Wendland, J., Philippsen, P. (2001). Cell Polarity and Hyphal Morphogenesis Are Controlled by Multiple Rho-Protein Modules in the Filamentous Ascomycete Ashbya gossypii. Genetics 157: 601-610 [Abstract] [Full Text]  
• Lengeler, K. B., Davidson, R. C., D'souza, C., Harashima, T., Shen, W.-C., Wang, P., Pan, X., Waugh, M., Heitman, J. (2000). Signal Transduction Cascades Regulating Fungal Development and Virulence. Microbiol. Mol. Biol. Rev. 64: 746-785 [Abstract] [Full Text]  
• Osherov, N., May, G. (2000). Conidial Germination in Aspergillus nidulans Requires RAS Signaling and Protein Synthesis. Genetics 155: 647-656 [Abstract] [Full Text]  
• Hurtado, C. A. R., Beckerich, J.-M., Gaillardin, C., Rachubinski, R. A. (2000). A Rac Homolog Is Required for Induction of Hyphal Growth in the Dimorphic Yeast Yarrowia lipolytica. J. Bacteriol. 182: 2376-2386 [Abstract] [Full Text]  
• Wendland, J, Philippsen, P (2000). Determination of cell polarity in germinated spores and hyphal tips of the filamentous ascomycete Ashbya gossypii requires a rhoGAP homolog. J. Cell Sci. 113: 1611-1621 [Abstract]  
• Feng, Q., Summers, E., Guo, B., Fink, G. (1999). Ras Signaling Is Required for Serum-Induced Hyphal Differentiation in Candida albicans. J. Bacteriol. 181: 6339-6346 [Abstract] [Full Text]  
• Harris, S. D. (1999). Morphogenesis is coordinated with nuclear division in germinating Aspergillus nidulans conidiospores. Microbiology 145: 2747-2756 [Abstract] [Full Text]  
• Harris, S. D., Hofmann, A. F., Tedford, H. W., Lee, M. P. (1999). Identification and Characterization of Genes Required for Hyphal Morphogenesis in the Filamentous Fungus Aspergillus nidulans. Genetics 151: 1015-1025 [Abstract] [Full Text]  
• Adams, T. H., Wieser, J. K., Yu, J.-H. (1998). Asexual Sporulation in Aspergillus nidulans. Microbiol. Mol. Biol. Rev. 62: 35-54 [Abstract] [Full Text]  
• Kaminskyj, S. G. W., Hamer, J. E. (1998). hyp Loci Control Cell Pattern Formation in the Vegetative Mycelium of Aspergillus nidulans. Genetics 148: 669-680 [Abstract] [Full Text]