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Acta Bot. Neerl.
311-320
35(3),August 1986, p,
microfilaments
of
and
J.
of
the
trichoblast
hyemale
equisetum
A.M.C. Emons
and
microtubules
Microfibrils,
Derksen
Department of Botany, University
of
ED
Nijmegen, Toemooiveld, 6525
Nijmegen,
The Netherlands
SUMMARY
The cell
wall of the trichoblastic
hair proper. The rotation
brils in
adjacent lamellae
During
During
trichoblast
root hair
axis of the
isodiametric
in microfibril
F-actin
interior.
1.
cortical
elongation
forming hair,
and root
not
the
hair cell
is helicoidal
of the helicoid is counter-clockwise
approximately
initiation
reveals microtubules in
enabling
is
of the root
part
mode
in
growth
parallel
apical
with
dome of the
lie
perpendicular
cortical microtubules
the
raicrofibrils.
forming hair,
Microtubules
expansion.
of the root
angle between
microfi-
40°.
microtubules
hair
like the cell wall
and the
in
these
axis of elongation.
to the
The freeze-substitution
where
cells
to the
align according
lie in random orientations
they
function
long
technique
in
but not
morphogenesis,
orientation.
cables, microfilaments,
They
do not
coalign with
present
are
in
the microfibrils
the
trichoblast; they
nor
with
form
a
network
in
the
cell
the microtubules.
INTRODUCTION
In many
plant cells,
found in
parallel
sized
do
to
so;
orientate the
and several
The
larging
were
paralellism
in the
& Bonnett
Recent
investigations
allow for such
an
on
et
while in time and in
place
al,
the
hairs
wall is
a
are
the
by
expected
Wolters-Arts
wall
1983).
new
deposited
been studied in
in
1982)
and in
& Seagull
out
en-
xylem
1985).
that microtubules
microfibril orientation
(New-
cells,
walls, however,
Emons &
did
Wolters-Arts
microtubules
not
1983,
align longitudinally
microfibrils attain all different orienta-
axis of the hair.
own
they
1982).
1980).
1982,
In these
adjacent
tip-growing cells (Sievers
secondary
(Falconer
hairs with helicoidal
their
& Seagull
especially
explained by pointing
(Emons
1985).
long
orientate the microfibrils
root
root
explanation
to
occurs
Seagull & Heath
Meekes 1985, Traas
tions with respect
of the
position
1965,
has
hypothe-
known how
not
Gunning & Hardham
thickening
has been
is, however,
proposed (Heath
structures
(Hardham 1982,
in which local wall
already
comb
have been
between these
cell surfaces
Absence of
microfibrils. It
nascent
hypotheses
coalignment
elements,
microfibrils and cortical microtubules have been
nascent
orientations and therefore microtubules have been
Therefore,
the microtubules
direction. It has
& Schnepf
the
1981)
to
be
cannot
emphasized
that
and that the helicoidal
non-enlarging
hair
tube
(Emons
&
312
F-actin
F-actin
cells
in
press).
Parthasarathy
They
involved
are
in
Parthasarathy
1984,
Equisetum hyemale
of
protuberance
an
their
investigate
to
al.
et
mechanism
2.
epidermis
AND
The microtubules
(Wick
& Duniec
of the
cytoplasm
TRAAsetal.
1983)
of boiled
pieces
frozen
0s0
to
and
held
vials, containing
at
temperature
a
material
was
another 6 h.
brought
At
aceton
several
Under
a
Fig. 1.
Width of
Fig.
2.
parabolae in
with
the wall
longer
in cells with
Fig.
section
the
of
last-deposited
cutive lamellae
is
a
root
from this
for the microfibrilorientat-
of
pieces
were
prior
to
more
last-deposited
Looking
thin-sectioning (Emons
by
al.
et
as
roots
grid.
a
1985).
of
with hairs
These
pieces
at
—
78 °C
transferred
aceton
in
a
a
spurr’s
uranyl
of
a
acetate,
trichoblast
embedding
helicoidal
x
,
and
arcs
The
device
20 h.
The
were
no
with
flat
layer.
evidence of gross
arcs
of sections.
a
present
anhydrous
a
growing root hair, prepared by
showing the
staining
are
rinsed with
of the helicoidal
13.200
x,
ice
freeze-
cell wall.
bar; 0.5
/an.
long growing
root
hair, prepared by
of the sections
with
permanganete.
in
the
proximal
of the hair
part
In
than
bar: 0.5 /an.
layer
of the cell wall
microfibril
from the
lamellae.
prepared by dry-cleaving
Arrows
cytoplasm, going
indicate
the
from former
occur in
and
direction
(a)
shadowing,
of the three
to latter
(b
resp.
angle between
c)
conse-
x, bar: 0.5 /im.
young root
indicate microtubules. Microtubules
were
containing
metal vial.
resin and embedded as
trichoblast with short
40°. 27.000
of very
rapidly
freeze-drying
to a
the rotation mode of the helicoid is counter-clockwise. The
tip
placed
were
were
by liquid nitrogen. They
anhydrous
individual hairs, showing
wall
immunofluorescence
by
visualized with the freeze-substitu-
also
micrograph depends on obliqueness
matrix
of
is
temperature in this apparatus very slowly during
staining with
approximately
4. Thin section
visualized
temperature the specimens
of the cell
lamellae.
and after
(± 5°C) by liquid nitrogen during
80°C
—
shorter root hairs. 27,300
deposited lamellae,
hair
root
originate
to
seem
a clue
precooled
infiltrated with
root hairs
three
&
1986) and
trichoblast. In this paper
before, during
hair
composed
acetate
3. Surface view of the innermost
showing
Fig
a
a
visualized
large
as
specimens
of the cell wall of
and on-block
Thin
dissolving
cells
the
to room
room
times,
Thin section
al.
et
interactions. A
propane, cooled
liquid
light microscope
substitution
were
were
dialysis tubing
0.1% uranyl
4
metal
Derksen
by dry-cleaving (Sassen
substitution fluid
a
1986,
streaming (Pesacreta
1984).
cell
root
were
freeze-substitution,
them in
by plunging
transferred
2%
For
procedure.
plant
al.
et
1985, Derksen
1985).
cell wall
and
Microfibrils and microtubules
on
of the
means
METHODS
The microfibrils of the
tion
by
be found in the trichoblast.
1983,
& Wolters-Arts
shown,
J, DERKSEN
microfilaments in trichoblasts of
possible
fibril lamellae of the
might
MATERIAL
al.
cell. This cell is called
epidermic
EMONS AND
normal component of
a
1985,
al.
et
cell
(Emons & Wolters-Arts 1983)
part of the
ing
be
et
microtubules and
trichoblast is used for the
term
hair formation. As
to
cytoplasmic
interact with microtubules (Pollard
We studied microfibrils,
been
recently
1985, Parthasarathy
(Parthasarathy
may
have
strands, microfilaments,
specific probe rhodamine-phalloidin,
Pierson
the
C.
A. M.
hair, prepared by
freeze-substitution.
random orientations.
13.200
x, bar;
Small
0.5/un.
arrows
THE TRICHOBLAST OF
EQUISETUM
HYEMALE
313
314
A. M.
crystal damage,
with
with
Sorvall
a
selected. The selected hairs
were
Porter
Blum
uranyl acetate/lead
Sections
were
examined with
phalloidin (Derksen
et
al.
in which the
to
and stained
a
EM 201 electron
Philips
cytoplasm
visualized
were
microscope.
rhodamine labelled
using
1986).
As is
preparation).
microtubule
preserve the
alignment
of the
cytoplasm
hair,
root
Sofar,
but the method did
in this part
(Emons
visual-
not
were
hair,
root
could be ascertained
the microfibrils of the cell wall
expected,
trichoblast cell wall.
the
of the
good preservation
longitudinal
ized by this method in the
in
tangentionally
grids
RESULTS
Freeze-substitution gave
in
sectioned
were
formvar coated
onto
J. DERKSEN
citrate.
The microfilamentsof the
3.
MT 5000
EMONS AND
C.
visualize microfibrils
of the cell
did
we
succeed
not
with cortical microtubules.
cytoplasm
The cell wall of the trichoblast is clearly of the helicoidal type (fig. 1). This
is also shown
face view
is
(fig. 2). Dry-cleaving
The
(fig. 3).
aproximately
latter
deposited
fibrils within
of material from which matrix substances has
by thin-sectioning
been dissolved
a
40°.
shows the
microhbnls in
last-deposited
between microfibrilorientations in
angle
from the
Looking
and
cytoplasm
sur-
lamellae
adjacent
from former
going
to
lamellae the rotation of the helicoid is counter-clockwise. Micro-
lamella are
not
contiguous.
The three different methods
employed
trichoblast is helicoidalwith the
sive lamellae and with the
same
show that the cell wall
angle
rotation of the helicoid
same
of the
texture
between fibril orientations of succesin the
as
root
hair cell
wall.
Fig.
tion.
short
5 shows the microtubulepattern in
Figs. 6a, b.
show
c
protuberance, (6b)
choblast with
a
full-grown
6a)
in
original
5. Microtubule
microtubule
align
(fig. 5).
is still
alignment
immunofluorescence.
alignment
hair. In
root
microtubule
the radial walls
Fig.
by
the
cell
epidermis
In
a
of undifferentiated
trichoblasts
and
6. a,
b, c.
Microtubule
alignment
fluorescence. Microtubules
mainly
protuberance, b) trichoblast, which
During hair growth microtubules
alignment is
Fig.
more or
7. Microfilament
lie
1000
in
a
in
a
the cortical
cytoplasm.
1200
x
.
tangential
of
part
a
tri-
a
are
cells
the
protuberance (fig.
wall is lost;
alignment
of the
elongation
(fig.
root
during cell elongation, visualized
the
to
same.
axis
Arrow
of
As
elongation.
designates long
to
axis of
.
root hair
growth, visualized by
cytoplasm, a) trichoblast,
growing hair, c) trichoblast, which
the direction
(6c)
root
during
of the
long
of the cell.
axis of the
960-1000
trichoblast, bearing a growing hair,
specific probe rhodamine-phalloidin. Microfilaments
in
hair and
root
root
transverse
in the cortical
less lost in the trichoblastic
alignment
x
hair forma-
cells before
epidermis
align
root
trichoblast with
a
the axis of elongation of the
the axis
in trichoblasts
has
growing
to
atrichloblasts
occur
(6a)
elongating epidermis
in the
to
microtubules
cells before
in
trichoblast with short
alignment
transverse
Cortical
a
transverse
of the cell.
root, which is the axis of elongation
Fig.
pattern
trichoblast with
a
hair initiation microtubules
and of the
epidermis
the microtubule
occur
at
x
has
a
hair;
immuno-
which has
a short
full-grown
after
hair.
growth
this
.
visualized
different levels
in
using the
the
cell,
F-actin
not
only
THE TRICHOBLAST OF EQUISETUM
HYEMALE
315
316
A. M.
Microtubules
6a).
the
hair
root
a
axis
long
hair. The
In
growth (fig. 6b).
hair all
full-grown
fibril
deposition
into
protrude
of the
in
regular
the
the
same
fig.
6c
hair and
forming
microtubule
it
be
can
microtubule
trichoblast goes
alignment
during
on
lie
that
is
in
is
pattern
seen
C. EMONS AND
the
direction of
conserved
in
these
during
trichoblast with
a
less lost. Micro-
more or
all
J. DERKSEN
stages
I
(figs.
and
2).
Freeze-substitution reveals
the
7 reveals the
Fig.
with
a
young
cytoplasm.
do
They
root
which
hair
growth
the
tip
of
microfilaments
a
trichoblast
situated in the cell
are
in the
predominantly
present
are
in
microfilaments,
hair. These microfilaments
microtubules,
Throughout
not
of F-actin cables,
alignment
growing
interior unlike
4.
random microtubule orientation in
a
protuberance (fig. 4).
this
conserve
cortical
alignment.
with the microfibrils of the cell wall.
coalign
DISCUSSION
Visualization
4.1.
of
microfibrils
by
of
means
freeze-substitu-
tion
Lead citrate and
The
1984).
uranyl
stains have
acetate
of cell walls after this
image
Cox & Juniper
stain cellulose
fore removed
(1972)
microfibrils,
by washing
have
stained with
staining
of the material
reveal microfibrils. The dark threads
block
uranyl
acetate
that
reported
but that this
chemical
no
on
seen
the
uranyl
is
in
material (fig.
therefore
are
interpreted
In freeze-fractured
male measured 8.5
3)
as
and
occur
in the
same
(+
1.5
deposit. However,
matrix has been dissolved
3.5
nm).
nm) including
microfibrils
much
possibility
the
that
crystalline
a
(fig. 2)
is
of
root
shadow
measure
layer
debate
on
1 and
positively
and
artefacts of chemical fixation
at
4.2.
Microtubules and
In
review
a
article,
on-
thin
shadowed
1985)
and
Equisetum hye-
1
(+
1985).
In
nm) including
the
(approximately
prepared
could
glucans,
with freeze-
point
at
the
which surrounds
stained.
microtubule
fibrils may be visualized
nm
which
2),
sheath ofless-crystalline
Emons & Wolters-Arts 1983, Lloyd
cause
8
of the wall
Freeze-substitution of on-block stained material is
date the
hairs of
deposit (Emons
their diameteris much smaller
larger (compare fig.
hydrophylic
core,
in
in thin sections of material from which the cell wall
The diameter in the helicoidal
substitution is
as in
as
cellulose microfibrils.
dry-cleaved preparations (fig. 3)
shadow
would
material
pattern
2),
and there-
staining
in freeze-etched material (Emons
as
preparations microfibrils
nm
nature
by freeze-substitution of
(fig. I)
& Levy
and lead citrate
On-block
sections from which matrix material has been dissolved (fig.
dry-cleaved
(Neville
acetate
physical
grids.
for cellulose.
affinity
is often unreliable
staining
same
are
microfibril
& Wells
ruled
out
time in the
one
of the
means to
coalignment
1985, Traas
et
(Emons
al.
eluci-
1982,
1985),
be-
and microtubules and micro-
same
preparation.
morphogenesis
Cormack
(1949)
stated that
there
was
general agreement
THE TRICHOBLAST OF
that retardation in vertical
cells
epidermal
317
EQUISETUM HYEMALE
rise
give
to
of the
elongation
trichoblasts is
It has become known since then that microtubule orientation is
of the
factors that
1985,
Hardham
uniformly
tion
in
determine the orientation of cell
Hardham
& Hardham
Sassen & Wolters-Arts this
can
root
plasts,
microtubules lie in random orientations
van
der
also in the
et
al. this
et
Valk
expanding
al.
tip
of
seems
also
be
the axis of
in
seen
elonga-
hairs
1984,
cells
epidermis
(M archant 1979,
root
&
expanding
isodiametrically expanding cells,
Equisetum hyemale
one
proto-
as
Lloyd
(fig. 4). (cf.
al.
et
occur
Derksen
issue).
cells microtubules
that
microtubule
a
the
trichoblast,
the
prerequisites
as
to
In cells
The random microtubule orientations
1980).
Cells, which have completed
In these
In
5).
least
Busby & Gunning
1982,
before
1980,
hair initiation (fig.
This
issue).
1984).
perpendicular
Hardham
1982,
at
elongation (Gunning
Busby & Gunning
1982,
direction microtubules lie
one
(Gunning
for
prerequisite
a
hairs.
to root
i.e.
according
the
same
long
the
to
needed to form
hyemale
form hairs
never
in random orientations
alignment perpendicular
atrichoblasts have the
Equisetum
elongation,
occur
a
hair,
axis
but it is
the
to
of the
not
the
elongating
not
axis of
hair
at
the
1949).
shown).
It
elongation
of
is
of
protuberance,
root
microtubule pattern and do
trichoblast stops
(Cormack
(data
one
initiating factor
form hairs.
not
of
onset
root
In
hair
formation.
Our observations clearly indicate a
bules:
at
the time that the
tangential
long
axis
of the
role of the cortical microtu-
forms microtubule
changes
protuberance.
The crucial
question
alignment along
the
and microtubules lie in the direc-
At the
of the
tip
and lie in random orientations
hemisphere
expansion.
protuberance
wall of the trichoblastic cell
tion of the
span the
morphological
protuberance they
allowing
for isodiametric
therefore is: ‘What factors determine microtu-
bule orientation?’
It further remains
in
tip-growing cells,
4.3.
to
be
microfibrils
along
are
basal
part
the whole
differing
the
(compare figs.
are
(figs.
deposited
I and
orientations
are
I
hair
is inhibited
expansion
alignment.
the
2). Thus,
deposited
microfibrils in
nascent
a
membrane. Across
root
hair and the cell wall of the tncho-
and
2).
As
microfibril
membrane,
growth,
deposition
helicoid, showing parabolae
lamellae with microfibrils in
while microtubules remain
statement
oc-
in the hair, microfibrils in this
to a
subsequently
helicoidal cell
wall
(Emons
in
aligned
that microtubules do
1982,
not
one
orien-
Emons &
1983).
Lloyd & Wells
(1985)
have
suggested
that
phosphate
disorientatetransversely oriented microtubules in
however, did
the
hair
according
direction only. This corroborates the
Wolters-Arts
plasma
root
Equisetum hyemale
of the cell
in thin sections.
against
deposited. During
blast thickens also
tate
transverse
Microtubules and microfibril orientation
Cortical microtubules lie
curs
how
explained
which have axial microtubule
not
root
buffer somehow would
hairs. Traas
et
al.
(1985),
find any differences in microtubule pattern between cells pro-
318
A. M.
cessed in
buffer and cells
phosphate
Lloyd & Wells
by
Microtubules and microfibrils influence
of
&
with
plant cell,
a
inner skeleton, with
shape, comparable
amoebae: Uyeda
role in
a
growing
cell parts.
enlarging
inner
and
cytoskeleton
a
role in
the
or
(erythrophores:
transient wall
alter the axis of
needs the
elongation.
bril
in
microfibrils,
orientation in
mesophyll
but
ment
not
Hahne &
Boergesenia.
during
cell wall
directly
4.4.
orientate the
in
parallel
nascent
(1985)
or
the
coalignment
& Brown
(Itoh
not
as
not
orientate
affect microfi-
have found that
cell division and cell
enlarge-
some
functions in common, microtu-
enlarging cells,
but microtubules do
not
microfibrils.
Microfilaments
The orientation of F-actin
cables, microfilaments,
visualized with rhodamine
labelled phalloidin, differs from the orientationof microtubulesand is
lated
to
the orientation of
observed
are
not
nascent
involved in cell
the microtubules
along
morphogenesis
nor
(Pollard
et
al.
in microfibril orientation.
Equisetum hyemale
in
(Emons
microfilaments
They
are
These filaments
preparation).
visualized with the rhodamine labelled
phalloidin.
tubules
not corre-
microfibrils. We conclude that the actin cables
In freeze-substituted root hairs of
seen
cells
deposition.
As microtubules and microfibrils have
bules and microfibrils lie in
Hoffmann
present during
are
skeleton
microtubules
because anti-microtubule agents did
cells microtubules
outer
Absence of
1982;
skeleton
full-grown
concluded that microtubules do
(1982)
Ochs
outer
permanently shaping cells. This
a
Microtu-
morphogenesis.
cell parts and permanent in
cell in
Mizuta & Wada
nascent
J, DERKSEN
maintenance and alteration
of microfibrils and microtubules has also been shown in Valonia
1984).
AND
buffer recommended
Microfibrils constitute the
1985).
more
cells
to
cell
plant
their role in animal cells
to
Furuya
is transient in
An
Pipes
EMONS
(1985).
bules constitute the
of cell
in
processed
C.
often
are
not
may interact with micro-
1984).
ACKNOWLEDGEMENTS
We thank
Dr.
Dr. T. Wieland
M. M. A. Sassen for
(Heidelberg) for
support
his
in various
generous
gift
of
rhodamine-phalloidinand
and
morphogenesis
Professor
ways.
REFERENCES
Busby,
C. H. & B.
fern Azolla;
Cormack,
E. S. Gunning
an
R. G.
(1984): Microtubules
unusual mode of guard cell and pore
H.
(1949):
The
development
of root
in stomata of the water
development.Proloplasma
hairs
in
Angiosperms.
122;108-119
Botanical
Rev.
15:
583-612.
Cox,
G.
&
B.
Juniper
(1972):
Electron
microscopy
of cellulose
in
entire
tissue. J.
Microsc.
97:
343-355.
Derksen, J.,
cells
of
Emons,
A.
wall.
J. A. Traas & T. Oostendorp
Equisetum hyemale root tips.
M. C.
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