Abstract
Phytophthora infestans is the causal agent of late blight, a notorious disease on potato and tomato that leads
to huge crop losses worldwide. The Phytophthora genus belongs to the oomycetes, a group of diverse
organisms that similar to fungi, grow as mycelium and produce spores to propagate. Oomycetes are best
known as plant pathogens but the group also comprises animal and microbial pathogens as well as
saprophytes. As such oomycetes occupy similar ecological niches as fungi. However, during evolution the
two groups evolved independently and this is reflected in differences in for example mating systems, cell
wall composition and biochemical and metabolic pathways. In our aim to pinpoint potential drug targets
in Phytophthora that can be exploited for disease control, we focus at identifying biological features unique
for oomycetes. In that respect the actin cytoskeleton, among others, caught our attention. This
intracellular framework is indispensable for the viability of eukaryotic cells and functions in a wide range
of processes including intracellular transport, formation of contractile rings, nuclear segregation,
endocytosis and facilitating apical cell expansions. We studied the actin cytoskeleton dynamics in
P. infestans in transgenic lines expressing the actin binding peptide Lifeact-eGFP. Fluorescence microscopy
showed that in hyphae actin filament cables and plaques are cortically localized. The distance between the
hyphal tip and the first actin filament plaque correlated strongly with growth velocity. Upon growth
termination, actin filament plaques appeared in the hyphal tip. The plaques were nearly immobile with
average lifetimes exceeding one hour; much longer (over 500-fold) than the lifetimes of actin patches in
fungi. Plaque assembly required ~30 seconds while disassembly took only ~10 seconds. In contrast to
actin patches in yeast, plaque disassembly was not accompanied with formation and internalization of
endocytic vesicles (Meijer et al. 2014, Cell. Microbiol.). We also investigated the in vivo actin dynamics
during early stages of pathogenesis. At the site of contact with the plant cell a condensed transient actin
structure was observed that resembles aster-like actin structures formed upon encountering hard
surfaces. Our results suggest that the actin cytoskeleton has distinct functions during the P. infestans
lifecycle. Future efforts will focus at identifying interactors and key regulators of the actin cytoskeleton
and pinpoint features in the actin network that are unique for oomycetes.
Original language | English |
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Title of host publication | Book of Abstracts 10th International Botanical Microscopy Meeting |
Pages | 33 |
Publication status | Published - 2015 |
Event | 10th International Botanical Microscopy Meeting, Exeter United Kingdom - Duration: 19 Apr 2015 → 23 Apr 2015 |
Conference
Conference | 10th International Botanical Microscopy Meeting, Exeter United Kingdom |
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Period | 19/04/15 → 23/04/15 |