A Ras protein from a phytopathogenic fungus causes defects in hyphal growth polarity, and induces tumors in mice |
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| Authors: | G M Truesdell C Jones T Holt G Henderson and M B Dickman |
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| Institution: | (1) Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln, NE 68583, USA e-mail: mbd@unlinfo.unl.edu Fax: +1-402-4722853, US;(2) Department of Veterinary and Biomedical Sciences, University of Nebraska-Lincoln, Lincoln, NE 68583, USA, US |
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| Abstract: | Ras is a low-molecular-weight guanine nucleotide (GDP/GTP)-binding protein that transduces signals for growth and differentiation
in eukaryotes. In mammals, the importance of Ras in regulating growth is underscored by the observation that activating mutations
in ras genes are found in many animal tumors. Colletotrichum trifolii is a filamentous fungal pathogen of alfalfa which causes anthracnose disease. To investigate signaling pathways that regulate
growth and development in this fungus, a gene encoding a Ras homolog (CT-Ras) was cloned from C. trifolii. CT-Ras exhibited extensive amino acid similarity to Ras proteins from higher and lower eukaryotes. A single amino acid change
resulting in mutationally activated CT-Ras induced cellular transformation of mouse (NIH 3T3) fibroblasts and tumor formation
in nu/nu mice. In Colletotrichum, mutationally activated CT-Ras induced abnormal hyphal proliferation and defects in polarized growth, and significantly reduced
differentiation in a nutrient-dependent manner. These results show that C. trifolii Ras is a functional growth regulator in both mammals and fungi, and demonstrate that proper regulation of Ras is required
for normal fungal growth and development.
Received: 20 October 1998 / Accepted: 23 April 1999 |
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| Keywords: | Colletotrichum trifolii Growth polarity Ras Signal transduction |
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