title: Rho1 and other GTP-binding proteins are associated with vesicles carrying glucose oxidase activity from Fusarium oxysporum f. sp. lycopersici.
abstract: In eucaryotic cells, the delivery of a secreted protein to the plasma membrane via vesicles must include transport, recognition, and fusion events. Proteins exposed on the cytoplasmic face of the secretory vesicles play a role in these events; these include the GTP-binding proteins, which are crucial components in this process. Fractions enriched with vesicles carrying glucose oxidase (GOX) activity from Fusarium oxysporum f. sp. lycopersici, a soilborne fungal pathogen causing vascular wilt on tomato plants, were obtained using two successive sucrose gradients, the first a linear-log and the second an isopycnic gradient. In this study, we used the following Fusarium strains: a wild-type and a strain carrying a Δrho1 loss-of-function mutation (presenting dramatically reduced virulence). By ADP-ribosylation with C3 exotoxin, and Western blot analysis with specific antibodies, we identified the small GTPases Rho1, Rho4, Cdc42 and Rab8, and a heterotrimeric Gα protein associated with vesicles carrying GOX activity. This was done for both strains, with the exception of Rho1, which was absent in the mutant strain; in addition, the levels of the Cdc42 protein were observed to be higher in the Δrho1 strain. These data indicate that three Rho proteins, Rho1, Rho4, and Cdc42, are present in secretory vesicles carrying GOX activity in F. oxysporum, and that Rho1 is not essential for the transport and secretion of, at least, cargo proteins carried in secretory vesicles, or Cdc42/Rho4 can fulfill its role in these events.
authors.affiliation: División de Ciencias Naturales y Exactas, Departamento de Biología, Campus Guanajuato, Universidad de Guanajuato, Apdo postal 187, 36000 Guanajuato, Gto, Mexico.
authors.forename: Karla
authors.initials: K
authors.lastname: Macías-Sánchez
authors.forename: Jesús
authors.initials: J
authors.lastname: García-Soto
authors.forename: Adriana
authors.initials: A
authors.lastname: López-Ramírez
authors.forename: Guadalupe
authors.initials: G
authors.lastname: Martínez-Cadena
mesh_terms: D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D005670:Fusarium / Q000235:genetics / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005949:Glucose Oxidase / Q000235:genetics / Q000378:metabolism*; D015151:Immunoblotting; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D005949:Glucose Oxidase; D019204:GTP-Binding Proteins; D020764:cdc42 GTP-Binding Protein; D020741:rho GTP-Binding Proteins