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)
Outline
(Brand & Gow, 2009)
Outline
(Brand & Gow, 2009)
Outline
(Brand & Gow, 2009)
Outline
(Brand & Gow, 2009)
Outline
(Brand & Gow, 2009)
Outline
(Brand & Gow, 2009)
Outline
(Brand & Gow, 2009)
Outline
(Brand & Gow, 2009)
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)
Re-cap
(Brand & Gow, 2009)
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)
Re-cap
(Brand & Gow, 2009)
Re-cap
(Brand & Gow, 2009)
Re-cap
(Brand & Gow, 2009)
Re-cap
(Brand & Gow, 2009)
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)
Re-cap
(Brand & Gow, 2009)
Figure 7: S. cerevisiae Bud5 interacts with Axl2
S10 = soluble fraction
b
b
a = haploid yeast
a/α = diploid yeast
b = untagged protein
(Kang et al., 2001)
diploid
Bright field
images
haploid
Figure 8: Bud5 localizes at pre-bud sites in both haploid and diploid S. cerevisiae cells
(Marston et al., 2001)
Figure 9: S. cerevisiae Bud2 & Bud5 localize at pre-bud sites
(Marston et al., 2001)
Re-cap
(Brand & Gow, 2009)
Re-cap
(Brand & Gow, 2009)
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)
Re-cap
(Brand & Gow, 2009)
Re-cap
(Brand & Gow, 2009)
Re-cap
(Brand & Gow, 2009)
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)
Re-cap
(Brand & Gow, 2009)
Figure 15: S. cerevisiae Cdc24 associates with Cdc42
GST-
(Mionnet et al., 2008)
Re-cap
(Brand & Gow, 2009)
Re-cap
(Brand & Gow, 2009)
Figure 16: S. cerevisiae Ste2 regulates far1
(A)
(B)
(Oehlen et al., 1996)
Conclusion
(Brand & Gow, 2009)
Take-Home Messages
• 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 ?
(Brand & Gow, 2009)
Proposed model for Ca2+ uptake in galvanotropic and thigmotropic growth
(Brand et al., 2007)
¿Tropic growth is facilitated by
polarized protein complexes ?
Tan Truong
BIOL 503
May 4, 2010
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