Tropic growth is facilitated by polarized protein complexes

Tropic growth is facilitated by polarized protein complexes Tan Truong BIOL 503 May 4, 2010

Tropism • Galvanotropism – growth in response to external electric field • Thigmotropism – growth in response to contact • Chemotropism – growth in response to chemicals • Geotropism/gravitropism – growth in response to gravity • Heliotropism/Phototropism – growth in response to sunlight • Hydrotropism – growth in response to water • Thermotropism – growth in response to temperature changes • Specific Host Tropism (amphotropism, neurotropism, etc.)

Galvanotropism C. albicans hyphal reorientation upon applied current (Brand et al., 2007)

Thigmotropism C. albicans hyphal reorientation upon surface ridge contact (Brand et al., 2007)

Chemotropism Neurospora crassa chemotropic attraction (Mak-2 localizing to CAT) (Gleissner et al., 2009)

Phototropism Phycomyces exhibiting phototropism (Bergman et al., 1969)

Fungal Species • Candida albicans - thin-walled, small budding yeast • Saccharomyces cerevisiae – model organism • Candida glabrata – non-dimorphic, haploid yeast; opportunistic pathogen; Candidemia

Outline (Brand & Gow, 2009)

Hypotheses • Environmental cues can induce tropism • Environmental cues can promote the uptake of other environmental cues, which can induce directional growth • Strategically-positioned receptors can facilitate tropism

Re-cap (Brand & Gow, 2009)

Figure 1: S. cerivisiae Mid1 is a stretch-activated Ca2+ channel Stretch described by (Murase et al., 2001) (Ozeki-Miyawaki et al., 2005)

Figure 2: Extracellular Ca2+ affects cathodal emergence of C. albicans hyphae (Brand et al., 2007)

Figure 3: Thigmotropic response is attenuated in C. albicans Ca2+–signaling –pathway mutants (Brand et al., 2007)

Figure 4: Proposed model for Ca2+ uptake in galvanotropic and thigmotropic growth (Brand et al., 2007)

Figure 5: Calcineurin is important for C. glabrata azole resistance Cnb1 = Calcineurin B subunit (Miyazaki et al., 2010)

Figure 6: Calcineurin & Crz1 regulate the expression of C. albicans Ca2+-dependent genes Cna = Calcineurin A subunit (Karababa et al., 2006)

Figure 7: S. cerevisiae Bud5 interacts with Axl2 b b S10 = soluble fraction a = haploid yeast a/α = diploid yeast b = untagged protein (Kang et al., 2001)

Figure 8: Bud5 localizes at pre-bud sites in both haploid and diploid S. cerevisiae cells haploid Bright field images diploid (Marston et al., 2001)

Figure 9: S. cerevisiae Bud2 & Bud5 localize at pre-bud sites (Marston et al., 2001)

Figure 10: Rsr1 & Bud2 are important for actin patch polarization in C. albicans Stained with Alexa phalloidin (actin) DIC microscopy (Hausauer et al., 2005)

Figure 11: C. albicans Rsr1 & Bud2 are important for hyphal morphogenesis (Hausauer et al., 2005)

Figure 12: Yeast Two-Hybrid (Y2H) Screening http://en.wikipedia.org/wiki/Two-hybrid_screening

Figure 13: S. cerevisiae Cdc24 interacts with both Far1 & Bem1 (Barale et al., 2004)

(Brand & Gow, 2009)

Figure 14: S. cerevisiae Cdc24 responds to α-factor (Barale et al., 2004)

Figure 15: S. cerevisiae Cdc24 associates with Cdc42 GST- (Mionnet et al., 2008)

Tropic growth is facilitated by polarized protein complexes