Browsing by Author "Campos, Cláudia"
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- Molecular mechanism for the control of virulent Toxoplasma gondii infections in wild-derived micePublication . Murillo-León, Mateo; Müller, Urs B; Zimmermann, Ines; Singh, Shishir; Widdershooven, Pia; Campos, Cláudia; Alvarez, Catalina; Könen-Waisman, Stephanie; Lukes, Nahleen; Ruzsics, Zsolt; Howard, Jonathan C; Schwemmle, Martin; Steinfeldt, TobiasSome strains of the protozoan parasite Toxoplasma gondii (such as RH) are virulent in laboratory mice because they are not restricted by the Immunity-Related GTPase (IRG) resistance system in these mouse strains. In some wild-derived Eurasian mice (such as CIM) on the other hand, polymorphic IRG proteins inhibit the replication of such virulent T. gondii strains. Here we show that this resistance is due to direct binding of the IRG protein Irgb2-b1CIM to the T. gondii virulence effector ROP5 isoform B. The Irgb2-b1 interface of this interaction is highly polymorphic and under positive selection. South American T. gondii strains are virulent even in wild-derived Eurasian mice. We were able to demonstrate that this difference in virulence is due to polymorphic ROP5 isoforms that are not targeted by Irgb2-b1CIM, indicating co-adaptation of host cell resistance GTPases and T. gondii virulence effectors.
- Plasma membrane H+-ATPases sustain pollen tube growth and fertilizationPublication . Hoffmann, Robert D.; Portes, Maria Teresa; Olsen, Lene Irene; Damineli, Daniel Santa Cruz; Hayashi, Maki; Nunes, Custódio O.; Pedersen, Jesper T.; Lima, Pedro T.; Campos, Cláudia; Feijó, José A.; Palmgren, MichaelPollen tubes are highly polarized tip-growing cells that depend on cytosolic pH gradients for signaling and growth. Autoinhibited plasma membrane proton (H+) ATPases (AHAs) have been proposed to energize pollen tube growth and underlie cell polarity, however, mechanistic evidence for this is lacking. Here we report that the combined loss of AHA6, AHA8, and AHA9 in Arabidopsis thaliana delays pollen germination and causes pollen tube growth defects, leading to drastically reduced fertility. Pollen tubes of aha mutants had reduced extracellular proton (H+) and anion fluxes, reduced cytosolic pH, reduced tip-to-shank proton gradients, and defects in actin organization. Furthermore, mutant pollen tubes had less negative membrane potentials, substantiating a mechanistic role for AHAs in pollen tube growth through plasma membrane hyperpolarization. Our findings define AHAs as energy transducers that sustain the ionic circuit defining the spatial and temporal profiles of cytosolic pH, thereby controlling downstream pH-dependent mechanisms essential for pollen tube elongation, and thus plant fertility.