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The actin cytoskeleton is a suppressor of the endogenous skewing behaviour of Arabidopsis primary roots in microgravity

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Before plants can be effectively utilised as a component of enclosed life-support systems
for space exploration, it is important to understand the molecular mechanisms
by which they develop in microgravity. Using the Biological Research in Canisters
(BRIC) hardware on board the second to the last flight of the Space Shuttle Discovery
(STS-131 mission), we studied how microgravity impacts root growth in Arabidopsis
thaliana. Ground-based studies showed that the actin cytoskeleton negatively regulates
root gravity responses on Earth, leading us to hypothesise that actin might also
be an important modulator of root growth behaviour in space. We investigated how
microgravity impacted root growth of wild type (ecotype Columbia) and a mutant
(act2-3) disrupted in a root-expressed vegetative actin isoform (ACTIN2). Roots of etiolated
wild-type and act2-3 seedlings grown in space skewed vigorously toward the
left, which was unexpected given the reduced directional cue provided by gravity. The
left-handed directional root growth in space was more pronounced in act2-3 mutants
than wild type. To quantify differences in root orientation of these two genotypes in
space, we developed an algorithm where single root images were converted into binary
images using computational edge detection methods. Binary images were processed
with Fast Fourier Transformation (FFT), and histogram and entropy were used to
determine spectral distribution, such that high entropy values corresponded to roots
that deviated more strongly from linear orientation whereas low entropy values represented
straight roots. We found that act2-3 roots had a statistically stronger skewing/
coiling response than wild-type roots, but such differences were not apparent on
Earth. Ultrastructural studies revealed that newly developed cell walls of space-grown
act2-3 roots were more severely disrupted compared to space-grown wild type, and
ground control wild-type and act2-3 roots. Collectively, our results provide evidence
that, like root gravity responses on Earth, endogenous directional growth patterns of
roots in microgravity are suppressed by the actin cytoskeleton. Modulation of root
growth in space by actin could be facilitated in part through its impact on cell wall
architecture.

Keywords: Actin; Arabidopsis; cell wall; microgravity; root development; space biology.

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Informasi Detail

Judul Seri

Plant Biology

No. Panggil

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Penerbit

: German Botanical Society and The Royal Botanical Society of the Netherlands., 2014

Deskripsi Fisik

Plant Biology 16 (Suppl. 1) (2014) 142–150

Bahasa

English

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Klasifikasi

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Tipe Isi

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Tipe Media

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Tipe Pembawa

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Edisi

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Subjek

PERTANIAN.

Info Detail Spesifik

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Pernyataan Tanggungjawab

agus

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