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The small GTP-binding protein Rho is expressed differentially during spore germination of Phycomyces blakesleeanus

Instituto de Investigación en Biología Experimental, Facultad de Química, Universidad de Guanajuato, Apartado Postal 187, Guanajuato, Gto, 36000 Mexico

ABSTRACT

Evidence has been obtained for the presence of the small 22 kDa GTP-binding Rho protein in dormant spores of Phycomyces blakesleeanus. Immunoblotting with a polyclonal antibody against RhoA revealed a soluble and membrane-associated 22 kDa protein. When [³²P]ADP-ribosylated by Clostridium botulinum C3 exotoxin the protein had a pl of 5·7, a value similar to that reported for other RhoA proteins. The 22 kDa protein was expressed at all stages of growth investigated, but radiolabelling of the [³²P]ADP-ribosylated protein increased when tube-formation occurred and decreased as the hyphae branched. Localization of RhoA during spore germination studied by immunofluorescence microscopy revealed the presence of RhoA in the cell membrane of the spore. When the spore started to swell, RhoA was observed as patches in the cell membrane which become concentrated in the neck region of the site of the protuberation tube, but this protein was never observed at the point of growth of the hyphal tip. The above results suggest that RhoA associated with one or more membrane proteins could participate in the molecular mechanism involved in maintaining cell integrity during the extrusion of the germ-tube of P. blakesleeanus.

Author for correspondence: Guadalupe Martínez-Cadena. Tel: +52 473 2 43 02. Fax: +52 473 2 43 02. e-mail: margua@quijote.ugto.mx

This article has been cited by other articles:

				J. Wendland and P. Philippsen Cell Polarity and Hyphal Morphogenesis Are Controlled by Multiple Rho-Protein Modules in the Filamentous Ascomycete Ashbya gossypii Genetics, February 1, 2001; 157(2): 601 - 610. [Abstract] [Full Text]

				J Wendland and P Philippsen Determination of cell polarity in germinated spores and hyphal tips of the filamentous ascomycete Ashbya gossypii requires a rhoGAP homolog J. Cell Sci., January 5, 2000; 113(9): 1611 - 1621. [Abstract] [PDF]