Plant
Science
193–
194 (2012) 48–
61
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Crystalline
and
amorphous
cellulose
in
the
secondary
walls
of
Arabidopsis
Katia
Ruel, Yoshiharu
Nishiyama, Jean-Paul
Joseleau
∗
Centre
de
Recherches
sur
les
Macromolécules
Végétales
(CERMAV-CNRS
UPR
5301),
BP
53
38041
Grenoble
CEDEX
9,
France
a
r
t
i
c
l
e
i
n
f
o
Article
history:
Received
16
November
2011
Received
in
revised
form
9
May
2012
Accepted
11
May
2012
Available online 18 May 2012
Keywords:
Crystalline
and
amorphous
cellulose
Xylem
cell
walls
Arabidopsis
Carbohydrate
binding
module
Microfibril
Ultrastructural
distribution
a
b
s
t
r
a
c
t
In
the
cell
walls
of
higher
plants,
cellulose
chains
are
present
in
crystalline
microfibril,
with
an
amorphous
part
at
the
surface,
or
present
as
amorphous
material.
To
assess
the
distribution
and
relative
occurrence
of
the
two
forms
of
cellulose
in
the
inflorescence
stem
of
Arabidopsis,
we
used
two
carbohydrate-binding
modules,
CBM3a
and
CBM28,
specific
for
crystalline
and
amorphous
cellulose,
respectively,
with
immuno-
gold
detection
in
TEM.
The
binding
of
the
two
CBMs
displayed
specific
patterns
suggesting
that
the
synthesis
of
cellulose
leads
to
variable
nanodomains
of
cellulose
structures
according
to
cell
type.
In
developing
cell
walls,
only
CBM3a
bound
significantly
to
the
incipient
primary
walls,
indicating
that
at
the
onset
of
its
deposition
cellulose
is
in
a
crystalline
structure.
As
the
secondary
wall
develops,
the
labeling
with
both
CBMs
becomes
more
intense.
The
variation
of
the
labeling
pattern
by
CBM3a
between
transverse
and
longitudinal
sections
appeared
related
to
microfibril
orientation
and
differed
between
fibers
and
vessels.
Although
the
two
CBMs
do
not
allow
the
description
of
the
complete
status
of
cellu-
lose
microstructures,
they
revealed
the
dynamics
of
the
deposition
of
crystalline
and
amorphous
forms
of
cellulose
during
wall
formation
and
between
cell
types
adapting
cellulose
microstructures
to
the
cell
function.
© 2012 Elsevier Ireland Ltd. All rights reserved.
1.
Introduction
Plant
cells
are
surrounded
by
a
cell
wall
made
of
polymer
com-
posite
organized
around
cellulose
microfibrils
(MFs).
Depending
on
the
developmental
stage,
the
tissue
type
and
the
cell
wall
layer,
the
MFs
are
differentially
embedded
in
pectic
polysaccharides,
hemicelluloses
and
lignin.
Many
fundamental
biological,
physi-
cal,
mechanical
and
chemical
properties
of
plants
depend
on
the
fine
organization
of
these
structural
polymer
constituents
at
the
ultrastructural
and
nanoscale
levels.
It
is
well
accepted
that
the
major
load-bearing
components
in
cell
walls
are
MFs
[1,2].
The
description
and
understanding
of
the
macromolecular
organization
of
native
cellulose
and
its
evolution
during
biosynthesis
are
essen-
tial
for
the
understanding
of
plant
cell
walls
architecture,
expansion
and
complex
cellulosic
materials
properties.
Cellulose
microfibrils
are
generally
considered
to
be
produced
at
the
cell
membrane
by
complexes
of
enzymes
that
polymerize
sev-
eral
cellulose
chains
simultaneously
[3].
The
first
structural
data
were
obtained
from
the
studies
of
algal
and
bacterial
celluloses
[4–6].
In
algal
cellulose,
the
crystal
lattice
image
extending
over
Abbreviations:
CBM,
cellulose
binding
domain;
MF,
microfibril;
MFA,
microfibril
angle;
TEM,
transmission
electron
microscopy.
∗
Corresponding
author.
Tel.:
+33
476
03
76
61;
fax:
+33
476
54
72
03.
E-mail
addresses:
joseleau@cermav.cnrs.fr,
jpjoseleau@gmail.com
(J.-P.
Joseleau).
the
whole
width
of
20-nm
wide
microfibrils
recorded
by
high-
resolution
transmission
electron
microscopy
[7],
lead
to
a
concept
that
microfibrils
are
in
fact
very
slender
single
crystals.
The
single
crystalline
nature
is
believed
to
be
due
to
the
kinetically
controlled
crystallization
at
the
biosynthesis
loci,
which
is
completely
differ-
ent
from
crystallization
process
of
polymers
that
crystallizes
from
melt
or
solution.
In
fact
native
cellulose
in
algae
or
bacteria
is
in
a
crystalline
form
where
all
the
chains
are
pointing
to
the
same
direc-
tion
since
the
polymerization
is
directional,
adding
monomers
to
the
non-reducing
ends
[8].
In
higher-plants
cellulose,
there
seems
to
be
weak
points
along
the
cellulose
microfibrils,
often
referred
to
be
as
“amorphous”,
about
every
100–150
nm
corresponding
to
the
level-off
degree
of
polymerization
when
acid
hydrolyzed.
Yet
the
neutron
small
angle
scattering
as
well
as
weight
loss
of
hydrolysis
suggested
this
highly
accessible
region
to
represent
only
about
1%
of
cellulose
[9].
In
this
case,
the
measured
crystallinity
may
be
considered
to
be
practically
100%.
In
X-ray
diffraction,
the
amorphous
is
characterized
by
the
absence
of
sharp
diffraction
peaks:
only
the
diffuse
scattering
feature
is
thought
to
be
representative
of
amorphous.
Separat-
ing
diffuse
scattering
from
broad
peak
is
much
dependent
on
the
assumption
of
peak
shape.
Thus
despite
the
huge
number
of
mea-
surements
of
crystallinity
or
lateral
sizes
of
microfibrils
of
different
cellulose
sample
in
the
literature,
the
values
are
at
best
rough
indi-
cators.
Crystallinity
is
also
often
assessed
by
solid-state
13
C
NMR
spectroscopy
where
amorphous
cellulose
and
chains
on
the
surface
0168-9452/$
–
see
front
matter ©
2012 Elsevier Ireland Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.plantsci.2012.05.008