The Plant Cell, Vol. 3, 629-635, June 1991 O 1991 American Society of Plant Physiologists
A Homolog of the Substrate Adhesion Molecule
Vitronectin Occurs in Four Species of Flowering Plants
Luraynne C. Sanders, Co-Shine Wang, Linda L. Walling, and Elizabeth M. Lord'
Department of Botany and Plant Sciences, University of California, Riverside,California 92521
The extracellular matrix (ECM) has been implicated in the primary developmental processes of many organisms. A
family of secretory adhesive glycoproteins called substrate adhesion molecules (SAMs) is believed to confer these
dynamic capabilities to the ECM in animals. In this paper, we report the existence of SAM-like genes and gene
products in flowering plants. Hybridizations with a human vitronectin cDNA probe and genomic DNA from broad
bean, soybean, and tomato revealed vitronectin-like sequences. Human vitronectin antibodies cross-react with a
55-kilodalton protein in leaf and root protein extracts from lily, broad bean, soybean, and tomato. In addition,
immunocytochemicalstaining of frozen sections of lily leaf and broad bean gynoecium demonstratedthat vitronectinlike proteins were localized to the ECM on the cell surface, with the most intense labeling residing in the transmitting
tract of broad bean gynoecium.
INTRODUCTION
Cells of all organisms produce products that are secreted
into the environment to form an extracellular matrix (ECM).
In plants, the ECM that encompasses each cell is referred
to as the cell wall (Lamport and Catt, 1981). The structural
role of the ECM, functioning in support and anchorage,
has long been recognized in both plants and animals
(Darvill et al., 1980; Hay, 1981). A more recent view of the
ECM suggests it has a more dynamic role in growth and
development (Adair and Mecham, 1990; Roberts, 1990).
The ECM in animal cells has been shown to play an active
role in developmental processes such as cellular polarity,
differentiation, cell division, cell death, and cell migration
(Hay, 1981; Hynes, 1981). These events are directed by a
variety of adhesion molecules (Edelman, 1988). Substrate
adhesion molecules (SAMs) are a family of adhesive glycoproteins that are secreted into the ECM and interact
with the cell by way of a class of plasma membrane
receptors known as integrins (Hynes, 1987). Many SAMs
have been described and localized in animal tissues; they
include fibronectin, laminin, vitronectin, and cytotactin
(Edelman, 1988). The SAMs that have been implicated in
facilitating cell spreading and/or cell migration during embryogenesis are vitronectin and fibronectin (Hayman et al.,
1983; Dufour et al., 1988). In vivo experiments have
demonstrated the importance of fibronectin in cell migration during embryogenesis. lnert latex particles placed
within the neural crest region of a chicken embryo translocated on the ECM in a pattern mimicking cell migration
(Bronner-Fraser, 1982). If these particles were coated with
' To whom correspondence should be addressed
fibronectin, however, translocation did not occur
(Bronner-Fraser, 1985). In vitro experiments showed that
cells and latex particles migrate preferentially on substrates containing fibronectin (Newman et al., 1985). The
more recently discovered vitronectin appears to be more
active biologically with regard to cell attachment, cell
spreading, and growth than fibronectin (Hayman et al.,
1985; Underwood and Bennett, 1989).
It has been suggested that a process similar to cell
migration may be operating in plants (Sanders and Lord,
1989). During pollination, a pollen tube extends through
the transmitting tract of the gynoecium, physically moving
its own protoplasm as well as two sperm cells to the
embryo sac in the ovule. The in vivo journey of pollen
tubes occurs within a specialized ECM called the stylar
matrix, which is secreted by the cells of the style (Knox,
1984). Based on data demonstrating active movement of
latex particles along the stylar ECM in three species of
flowering plants, we have suggested that the style actively
facilitates pollen tube extension by way of a biochemical
recognition-adhesion system (Sanders and Lord, 1989).
This hypothesis suggests that a pollen tube tip can be
considered as analogous to a migrating cell, which leaves
a trai1 of cell wall behind. The hypothesis also implies the
presence of SAMs and their receptors in plants. Recently,
Schindler et al. (1989), using a vitronectin receptor monoclonal antibody, detected proteins similar to the 0-subunit
of the human vitronectin receptor (an integrin) in cultured
soybean cells. This implies the presence of integrin-like
protein in plants. Here, we describe what may be a plant
SAM. Using human vitronectin cDNA probes and human
630
The Plant Cell
VN 1 2 3 4 5 6 7 V N 1 2 3 4 5 6
7
kD
97.4 —
66.2 —
45.0 —
31.0 —
21.5 —
14.4 —
B
Figure 1. Detection of a 55-kD Plant Protein by Human Vitronectin Antiserum.
Lanes 1 to 7 are protein extractions from plant tissue: lanes 1, lily leaf; lanes 2, lily root; lanes 3, broad bean leaf; lanes 4, broad bean
root; lanes 5, soybean leaf; lanes 6, soybean root; lanes 7, tomato leaf. The lanes labeled VN contain 100 ng of purified human vitronectin.
(A) Protein blot incubated with human vitronectin antiserum.
(B) Protein blot incubated with nonimmune serum.
vitronectin antibodies, we were able to detect vitronectinlike genes and proteins in four species of flowering plants.
Fluorescent-labeled anti-human vitronectin antibody localized these proteins to the inner wall in sections of leaf,
root, and gynoecial tissues.
RESULTS
Proteins were extracted from the leaves and roots of lily,
broad bean, soybean, and tomato, fractionated on 13%
SDS-polyacrylamide gels, and transferred to nitrocellulose.
Figures 1A and 1B show protein blots that were incubated
with human vitronectin antiserum or nonimmune serum. In
all four species and in both organs, a single 55-kD crossreactive band was resolved strongly (Figure 1A). Minor
protein bands were observed upon longer development.
These proteins are likely to have a decreased affinity for
the human vitronectin antibodies or may represent nonspecific binding from the antiserum. The blot incubated in
nonimmune serum detected no cross-reactive molecules
(Figure 1 B). To investigate immunological relatedness of
human vitronectin and the 55-kD protein from plants, we
used purified human vitronectin to block the immunological
reaction in immunoblots, as shown in Figure 2. Immunoglobulins (Ig) were purified from the human vitronectin
antiserum and their molar concentrations determined. Partial blots were then incubated in either the purified IgG,
used as a control (Figure 2A), in purified IgG preincubated
in a 10 M excess of human vitronectin (Figure 2B), or in
purified IgG preincubated in a 10 M excess of BSA, used
as an additional control (data not shown). Reduction of the
immunological reaction occurred only when the purified
IgG was preincubated with human vitronectin (Figure 2B).
The protein bands affected were the 75-kD and 65-kD
human vitronectin, which were eliminated, and the 55-kD
proteins from extracts of broad bean leaf and root, which
were reduced strikingly when compared with the control
(Figure 2). The protein band observed at the bottom of the
blots was not affected by the treatment and therefore
probably represents background from other antibodies in
the antiserum, i.e., not a specific reaction between the
vitronectin antibodies and a plant protein. The blot incubated in the purified IgG preincubated with BSA was
identical to the control (data not shown).
To demonstrate further immunological relatedness between human vitronectin and the 55-kD protein in plants,
we used monospecific antibodies purified from either human
vitronectin or the 55-kD protein from lily and broad bean
roots. The monospecific anti-human vitronectin antibody
recognized a major band at 55 kD in all three plant species
and both organs, as shown in Figure 3A. A few minor bands
were recognized in all five lanes. Conversely, the monospecific anti-55-kD root antibody was immunologically reactive
Homolog of Vitronectin Is in Plants
VN 1
2
VN 1
7565-
631
VN 1 2 3 4 5
kD
97.4 —
55-
66.2 —
45.0 —
B
Figure 2. Reduction of Immuno-Cross-Reactivity in the Presence
of Human Vitronectin.
Lanes 1 and 2 are protein extractions from broad bean leaf and
root tissue, respectively. The lanes labeled VN contain 100 ng of
purified human Vitronectin.
(A) Protein blot incubated with purified IgG from human Vitronectin
antiserum.
(B) Protein blot incubated with purified IgG from human Vitronectin
antiserum preincubated with purified human Vitronectin.
31.0 —
21.5 —
14.4 —
VN 1 2 3 4
with both the 65-kD and 75-kD human Vitronectin proteins,
as well as the 55-kD protein from leaf extracts of lily, broad
bean, and soybean, as shown in Figure 3B. Only one minor
band was recognized in lane 3, broad bean leaf proteins,
and most likely represents a breakdown product of the 55kD protein. Identical blots, when incubated with monospecific antibodies made from nonimmune serum instead of
human Vitronectin antiserum, detected no proteins (data
not shown).
Localization of vitronectin-like proteins by immunofluorescence on frozen sections of lily leaves and broad bean
gynoecium is shown in Figure 4. Slides were incubated
with human Vitronectin antiserum or, as controls, incubated in nonimmune serum or secondary antibody only.
Frozen sections of lily leaf incubated with human vitronectin antiserum revealed a ubiquitous vitronectin-like protein
in the tissue. The fluorescence appeared in patches in the
innermost part of the wall of all cells in the leaf (Figure 4B).
Cross-sections of broad bean gynoecial tissue had a similar pattern of fluorescence distribution in all cells, except
the transmitting tract, in which the fluorescence was more
intense and continuous (Figure 4E). Frozen sections of leaf
or gynoecium incubated with rabbit nonimmune serum
(Figures 4C and 4F) or secondary antibody only (data not
shown) showed limited fluorescence, which was slightly
more than autofluorescence (data not shown). Root tissue
of lily was also frozen, sectioned, and incubated in the
human Vitronectin antiserum as described above. These
tissues revealed a similar distribution of the vitronectin-like
proteins (data not shown). Frozen sections of broad bean
5
kD
97.4 —
66.2 —
45.0 —
31.0 —
21.5 —
14.4 —
B
Figure 3. Immuno-Cross-Reactivity Using Monospecific Antibody.
Lanes 1 to 5 are protein extractions from plant tissue: lanes 1, lily
leaf; lanes 2, lily root; lanes 3, broad bean leaf; lanes 4, broad
bean root; lanes 5, soybean leaf. The lanes labeled VN contain
150 ng (A) or 3 ng (B) of purified human Vitronectin.
(A) Protein blot incubated with monospecific antibodies purified
from human Vitronectin.
(B) Protein blot incubated with monospecific antibodies, purified
from the 55-kD protein of lily and broad bean root.
632
The Plant Cell
tissue were incubated with anti-human fibronectin antibody, but results were inconclusive.
To determine whether plant vitronectin-like sequences
could be detected using a heterologous vitronectin cDNA
probe, genomic DMA blots were hybridized with a 32Plabeled human vitronectin cDNA probe. Ten micrograms
of genomic DMA from the leaves of lily, broad bean,
soybean, and tomato were digested, fractionated on 1%
agarose gels, and transferred to a nylon membrane. Several DMA fragments in broad bean, soybean, and tomato
were visualized with the human vitronectin probe, as
shown in Figure 5. These bands persisted when the membrane was washed under stringent conditions. We were
unable to detect any vitronectin-like sequences in lily using
the procedure described above. Similar experiments using
fibronectin cDNA probes were negative.
DISCUSSION
Figure 4. Localization of a Vitronectin-like Protein on Frozen
Sections.
(A) to (C) Lily leaf cross-sections.
(D) to (F) Broad bean gynoecium cross-sections.
(A) Section stained with toluidine blue O; x400.
(B) Section incubated with human vitronectin antiserum; x400.
(C) Section incubated with nonimmune serum; x400.
(D) Section of gynoecium stained with toluidine blue 0; boxed
area indicates transmitting tract; x50.
(E) Section of transmitting tract incubated with human vitronectin
antiserum; x495.
(F) Section of transmitting tract incubated with nonimmune serum;
X495.
E, epidermis; M, mesophyll; C, cuticle. White arrows indicate
areas of immunoreactivity.
In three of the plant species examined, DNA gel blot
analysis showed several DNA fragments hybridized with
human vitronectin probe. These data suggest that a family
of genes with similarity to human vitronectin may exist in
these plant genomes. Even though no vitronectin crosshybridizing DNA fragments were visualized with the lily
DNA, the immunoblots (Figures 1A and 3) and immunofluorescence studies (Figure 4B) indicated that a vitronectinlike product exists in this species. The fact that the lily
genome is 10 to 50 times larger than the other three
species examined may explain why strong hybridization
signals were not observed (Bennett and Smith, 1976).
Immunoblot analysis using the human vitronectin antiserum revealed one major band at 55 kD in four plant
species and in different organs. The immunoreactivity of
this protein was greatly reduced in the presence of human
vitronectin. Furthermore, monospecific anti-human vitronectin antibody cross-reacted with the 55-kD protein. Monospecific anti-55-kD-root antibody cross-reacted with the
55-kD protein in leaves of three species and the 65-kD
and 75-kD human vitronectin proteins. These data demonstrated that the 55-kD proteins from these four plant
species are immunologically related to human vitronectin.
It is not surprising that a higher amount of the human
vitronectin protein was needed to achieve a noticeable
immunological reaction with the monospecific anti-55-kD
root antibody because it is unlikely that epitope conservation is very high between plant and human vitronectin.
Although the molecular weight of the vitronectin-like protein in plants differs from that of human vitronectin, the
molecular weight of animal vitronectins examined ranges
from 56,000 to 80,000 (Kitagaki-Ogawa et al., 1990). The
plant protein fits into the lower end of this scale. Frozen
sections of lily and broad bean tissues incubated with
human vitronectin antiserum localized the vitronectin-like
Homolog of Vitronectin Is in Plants
1
2
B B P B B
Hi Hi Hi Hi Hi
VN
Ha
bp
5090407230542036-
1636-
1018-
517-
Figure 5. Detection of Vitronectin-like Sequences Using DNA
Hybridization Gel Blot Analysis.
Lanes 1 to 4 represent genomic DNA from lily, broad bean,
soybean, and tomato, respectively. All lanes were hybridized with
a human 32P-labeled vitronectin cDNA probe. Two picograms of
human vitronectin cDNA served as a positive control (VN). The
position of the 1-kb DNA ladder (Bethesda Research Laboratories)
markers are indicated. B, BamHI; Ha, Haelll; Hi, Hindlll; P, Pvull.
proteins to what we believe is the cell surface. Vitronectin
is a secretory protein in animals and this is likely to be the
case in plants. Sequencing of the vitronectin-like genes
and gene products in plants is necessary to determine the
degree of similarity between plant and human vitronectin.
Although we detected no fibronectin cross-hybridizing sequences in plant genomic DNA, the possibility remains that
other SAMs occur in plants. Together, the genomic DNA
blot, immunoblot, and immunofluorescence studies are
strong evidence that a molecule similar to human vitronectin exists in plants.
The fact that a SAM-like molecule, which has been
implicated in facilitating cell spreading and/or migration in
animal systems, occurs in plants lends credence to the
proposal that pollen tube extension is a special case of
633
cell migration in plants (Sanders and Lord, 1989). Immunolocalization with the human vitronectin antiserum
showed a strong reaction on the transmitting tract cell
surfaces that function to support pollen tubes (Figure 4E).
Based on these results and previous work (Sanders and
Lord, 1989), as well as the extensive literature on pollination, we propose that compatible pollen tube extension in
the gynoecium occurs in a manner similar to cell migration
in animal systems. A model reported by Thiery's group
(Dufour et al., 1988) explains the role of SAMs in stationary
cell adherence as well as the transitory adherence that
occurs during cell motility. In the stationary cell, the binding
affinity of the SAM for its integrin is strong and the microfilaments of the cell bind to the integrin indirectly, forming
a tight connection with the cytoskeleton and creating focal
adhesions (Burridge et al., 1988). In the motile cell, the
affinity between the SAM and its integrin is weak and only
transitory attachments occur, with the microfilaments
forming a loose arrangement. Recent literature on the
cytoskeleton of the pollen tube shows a loose arrangement of microfilaments at the growing tip and a more
organized cytoskeleton further back from the tip (Lancelle
et al., 1987; Tiwari and Polito, 1988; Heslop-Harrison and
Heslop-Harrison, 1989). In this region of stationary adherence, structures resembling focal adhesions occur, but
only in pollen tubes grown in vivo, not in those grown in
vitro (Pierson et al., 1986).
Detection of the vitronectin-like protein in all tissues
examined suggests that it may have a more basic function,
perhaps in linking the cytoskeleton to the cell wall. In animal
cells, SAMs function as links between the cytoskeleton
and the ECM by way of the transmembrane integrin (Bissell
et al., 1982; Burridge et al., 1988; Dufour et al., 1988).
Green's (1986) work on the biophysics of organogenesis
in plants suggests a connection between the cytoskeleton
and the microfibrils of cellulose in the wall. We propose
that, in plants, a SAM such as vitronectin may provide this
link by way of an integrin-like protein in the plasma membrane (Schindler et al., 1989). SAMs, like the one described
here, may provide the ECM of plants with a dynamic
scaffolding that can function in development, communication, and, in a specialized case, cell movement during
pollination.
METHODS
Immunoblot Analysis
In this study, we used tissue from lily (LJIium longiflorum), broad
bean (We/a faba), soybean (Glycine max), and tomato (Lycopersicon esculentum).
Leaf or root tissue was immersed in liquid nitrogen and ground
in a mortar with pestle. Proteins were extracted by transferring
samples directly into boiling SDS (12% w/v), 200 mM Tris, 100
mM DTT, pH 8.4 (Smith and Fisher, 1984) using 4 volumes for
634
The Plant Cell
leaf tissue and 1.5 volumes for root tissue. The samples were
centrifuged at 15,0009 for 5 min. The supernatant was collected;
aliquots (15 pL to 30 pL for leaf tissue and 35 pL for root tissue)
from each sample and 100 ng of purified human vitronectin (D.
Cheresh, Departmentof Immunology,Scripps Clinic and Research
Foundation, La Jolla, CA; Telios Pharmaceuticals,Inc., San Diego,
CA) were fractionatedon 13% SDS polyacrylamide gels (Laemmli,
1970). The gels were either stained with 0.2% Coomassie Brilliant
Blue R or electroblotted onto nitrocellulose. Molecular weight
markers were purchased from Bio-Rad. Blots were blocked with
3% gelatin in 0.1% Tween 20, Tris-bufferedsaline (0.1% TTBS);
20 mM Tris, 500 mM NaCI, pH 7.5 (TBS). Blots were incubated
for 1 hr with rabbit anti-human vitronectin serum (Telios Pharmaceuticals, Inc.) at a dilution of 1:500, or incubated for 1 hr in rabbit
nonimmune serum at a dilution of 1500. lmmunoblots were
washed three times in 0.1% TTBS, incubated in a secondary
antibody (goat anti-rabbit IgG alkaline phosphatase conjugate;
Bio-Rad) for 1 hr at a dilution of 1:3000. Blots were then washed
three times in 0.1% TTBS and two times in TBS and incubated
with color development solution (Bio-Rad).
Purification of IgG from the human vitronectin antiserum was
achieved by using an Econo-Pac Protein A Kit (Bio-Rad) per the
manufacturer's instructions. The molar concentrationof 1 mL of
purified IgG was determined by using a Beckman DU-6 spectrophotometer (AzBo).,
Aliquots of the purified IgG, diluted 1:1, were
preincubated with a 1O M excess of purified human vitronectin or
BSA (Sigma)for 15 min. Three partia1blots, prepared as described
above, were incubated for 1 hr either in the purified IgG diluted
1:1, or with purified IgG preincubated with purified human vitronectin or BSA, used as a control.
Monospecific antibodies were purified from human vitronectin
and a mixture of the 55-kD proteins from lily and broad bean
roots. The 55-kD proteins were excisedfrom a blot on which 500
pg of total proteins from the roots were fractionated and transferred. Forty micrograms of purified human vitronectin was excised from a blot. The excised proteinswere separately incubated
in either the human vitronectin antiserum or rabbit nonimmune
serum (used as a control) at a dilution of 1:50. The monospecific
antibodies were eluted by a low pH buffer and neutralized by 1 M
sodium phosphate buffer (pH 7.7) as described by Smith and
Fisher (1984). lmmunoblots were prepared as described above
with the following modifications: proteins were extracted by using
a phenol extraction method as described by Hurkmanand Tanaka
(1986), proteins of each sample were quantitated by the Byadford
protein assay (Bradford, 1976), and 50 pg of total protein from
each sample was fractionated and transferred. The amount of
purified human vitronectin transferred to the immunoblots varied
with the monospecific antibody in which the blot was incubated:
150 ng for blots incubated in the monospecific anti-human vitronectin antibody and 3 pg for blots incubated in the monospecific
anti-55-kD root antibody. Blots were incubated in the monospecific antibodies overnight at 4OC.
and collected on slides subbed with 0.5% gelatin and 0.005%
chrome alum (Pappas, 1971). Sections were blocked with 0.1%
TTBS, incubated for 1 hr in either human vitronectin antiserum at
a dilution of 1:300 or, as a control, rabbit nonimmune serum at a
dilution 1:300 for 1 hr. Slides were rinsed three times in 0.1%
TTBS, then incubated in the secondary antibody (goat anti-rabbit
IgG biotinylated; ICN lmmuno Biological, Irvine, CA) for 1 hr. Some
slides were blockedand incubated in the secondary antibody only,
as an additional control. All slides were then washed three times
in 0.1% TTBS, incubated for 30 min in a fluorescein isothiocyanate-avidin conjugate (ICN lmmuno Biological) diluted 1:200,
and rinsed three times in 0.1% TTBS and twice in TBS. Sections
were viewed with a Zeiss fluorescence microscopeequipped with
Zeiss filter set 487716 and Ealing interference filter 35-5347, a
560 nm shortwave pass filter used to block chloroplast autofluorescence, or Omega qualitative analysis filter set for fluorescein
isothiocyanate. For light micrographs, cryosections were stained
with 0.5% aqueous toluidine blue O (Sigma). Kodak 2415 Technical Pan film was used for light micrographs and Kodak Tri-X for
fluorescence micrographs.
DNA Gel Blot Analysis
Genomic DNA was extracted using the procedure of Dellaporta
et al. (1983), purified by CsCl density gradient centrifugation.Ten
micrograms of genomic DNA was digested with restriction enzymes and fractionated on 1% agarose gels and transferred to
a zeta-probe membrane (Bio-Rad) under conditions suggested
by the manufacturer. The membrane was hybridized with a
3zP-labeledhuman vitronectincDNA (Telios Pharmaceuticals,Inc.).
Hybridization was as described previously (Walling et al., 1988)
with the following modifications: hybridization buffer contained
40% formamide, and the blot was incubated at 33°C. The membrane was washed twice for 20 min in 0.1 times standard saline
citrate (149 mM NaCI, 15 mM Na citrate) and 0.1% SDS at 50°C.
The blot was exposed to Kodak XARS film with one screen for
48 hr.
ACKNOWLEDGMENTS
We thank Drs. Eugene Nothnagel, Carl Ware, Timothy Close, and
David Cheresh for discussion and advice. We are grateful to Dr.
David Cheresh for the generous gift of human vitronectin. This
research was supported by National Science Foundation Grant
PCM 88-18554 to E.M.L.
Received April 1, 1991; accepted April 17, 1991
lmmunolocalization
REFERENCES
Leaf and gynoecium samples were embedded in Tissue-Tek OCT
compound (Miles Laboratories, Inc., Elkhart, IN) and frozen in
freon precooled with liquid nitrogen. The tissue was cut at 16 pm
for leaf tissue and 8 pm for gynoecium tissue on a MicrotomeCryostat (International Equipment Co., Needham Heights, MA)
Adair, W.S., and Mecham, R.P. (1990). Organization and Assembly of Plant and Animal Extracellular Matrix, W.S. Adair and
R.P. Mecham, eds (New York: Academic Press).
Homologof Vitronectin 1s in Plants
Bennett, M.D., and Smith, J.B. (1976). Nuclear DNA amounts in
angiosperms. Philos. Trans. R . SOC.Lond. B 274,227-259.
Bissell, M.J., Hall, H.G., and Parry, G. (1982). How does the
extracellular matrix direct gene expression? J. Theor. Biol. 99,
31-68.
Bradford, M.M. (1976). A rapid and sensitive method for the
quantitation of microgram quantities of protein utilizing the
principle of protein-dyebinding. Anal. Biochem. 72, 248-254.
Bronner-Fraser, M. (1982). Distributionof latex beads and retina1
pigment epithelial cells along the ventral neural crest pathway.
Dev. Biol. 91, 50-63.
Bronner-Fraser, M. (1985). Effects of different fragments of the
fibronectin molecule on latex bead translocation along neural
crest migratory pathways. Dev. Biol. 108, 131-1 45.
Burridge, K., Fath, K., Kelly, T., Nuckolls, G., and Turner, C.
(1988). Focal adhesions: Transmembrane junctions between
the extracellular matrix and the cytoskeleton. Annu. Rev. Cell
Biol. 4,487-525.
Darvill, A., McNeil, M., Albersheim, P., and Delmer, D.P. (1980).
The primary cell walls of flowering plants. In The Biochemistry
of Plants, Vol. 1, N.E. Tolbert, ed (New York: Academic Press),
pp. 91-1 62.
Dellaporta, S.L., Wood, J., and Hicks, J.B. (1983). A plant
minipreparation. Plant MOI.Biol. Rep. 1, 19-23.
Dufour, S., Duband, J.-L., Kornblihtt, AR., and Thiery, J.P.
(1988). The role of fibronectins in embryonic cell migrations.
Trends.Genet.4, 198-203.
Edelman, G.M. (1988). Topobiology: An lntroduction to Molecular
Embryology. (New York: Basic Books. lnc.).
Green, P.B. (1986). Plasticity in shoot development: A biophysical
view. In Society for Experimental Biology Symposium 40, D.H.
Jennings and A.J. Trewavas, eds (Cambridge, England: The
Company of Biologism Ltd.), pp. 211-232.
Hay, E.D. (1981). Collagen and embryonic development. In Cell
Biology of Extracellular Matrix, E.D. Hay, ed (New York: Plenum
Press), pp. 379-409.
Hayman, E.G., Pierschbacher, M.D., and Ruoslahti, E. (1983).
Serum spreading factor (vitronectin)is present at the cell surface
in tissues. Proc. Natl. Acad. Sci. USA 80, 4003-4007.
Hayman, E.G., Pierschbacher, M.D., Suzuki, S., and Ruoslahti,
E. (1985). Vitronectin-a major cell attachment-promotingpro-
tein in fetal bovine serum. Exp. Cell Res. 160, 245-258.
Heslop-Harrison,J., and Heslop-Harrison,Y. (1989) Conforma-
tion and movement of the vegetative nucleus of the angiosperm
pollen tube: Association with the actin cytoskeleton.J. Cell Sci.
93,299-308.
Hurkman, W.J., and Tanaka, C.K. (1986). Solubilization of plant
membrane proteinsfor analysis by two-dimensional gel electrophoresis. Plant Physiol. 81, 802-806.
Hynes, R.O. (1981). Fibronectin and its relation to cellular structure and behavior. In Cell Biology of Extracellular Matrix, E.D.
Hay, ed (New York: Plenum Press), pp. 295-334.
Hynes, R.O. (1987). Integrins: A family of cell surface receptors.
Cell48, 549-554.
635
Kitagaki-Ogawa, H., Yatohgo, T., Izumi, M., Hayashi, M., Kashiwagi, H., Matsumoto, I., and Seno, N. (1990). Diversities in
animal vitronectins. Differences in molecular weight, immunoreactivity and carbohydrate chains. Biochim. Biophys. Acta
1033,49-56.
Knox, R.B. (1984). Pollen-pistil interactions. Annu. Rev. Plant
Physiol. 17, 508-608.
Laemmli, U.K. (1970). Cleavage of structural proteins during the
assembly of the head of the bacteriophage T4. Nature 227,
680-685.
Lamport, D.T.A., and Catt, J.W. (1981). Glycoproteins and enzymes of the cell wall. In Plant Carbohydrates, Vol. II: Extracellular Carbohydrates, W. Tanner and F.A. Loewus, eds (New
York: Springer-Verlag), pp. 134-1 65.
Lancelle, S.A., Cresti, M., and Hepler, P.K. (1987). Ultrastructure
of the cytoskeleton in freeze-substitutedpollen tubes of Nicofiana alafa. Protoplasma 140, 141-1 50.
Newman, S.A., Frenr, D.A., Tomasek, J.J., and RaburZi, D.D.
(1985). Matrix-driventranslocation of cells and nonliving particles. Science 228, 885-888.
Pappas, P.W. (1971). The use of a chrome alum-gelatin (subbing)
solution as a general adhesive for paraffin sections. Stain Technol. 46, 121-124.
Pierson, E.S., Dirksen, J., and Traas, J.A. (1986). Organization
of microfilaments and microtubules in pollen tubes grown in
vitro or in vivo in various angiosperms. Eur. J. Cell Biol. 41,
14-1 8.
Roberts, K. (1990). Structures at the plant cell surface. Curr. Op.
Cell Biol. 2, 920-928.
Sanders, L.C., and Lord, E.M. (1989). Directed movement of
latex particles in the gynoecia of three species of flowering
plants. Science 243, 1606-1608.
Schindler, M., Meiners, S., and Cheresh, D.A. (1989). RGDdependent linkage between plant cell wall and plasma membrane: Consequences for growth. J. Cell Biol. 108,1955-1965.
Smith, D.E., and Fisher, P.A. (1984). Identification,developmental
regulation, and response to heat shock of two antigenically
relatedforms of a major nuclear envelope protein in Drosophila
embryos: Application of an improved method for affinity purification of antibodies using polypeptides immobilized on nitrocellulose blots. J. Cell Biol. 99, 20-28.
Tiwari, S.C., and Polito, V.S. (1988). Organization of the cytoskeleton in pollen tubes of Pyrus communis: A study employing
conventional, and freeze-substitutionelectron microscopy, immunofluorescenceand rhodamine-phalloidin.Protoplasma 174,
100-1 12.
Underwood, P.A., and Bennett, F.A. (1989). A comparison of the
biological activities of the cell-adhesive proteins vitronectin and
fibronectin. J. Cell Sci. 93, 641-649.
Walling, L.L., Chang, Y.C., Demmin, D.S., and Holrer, F.M.
(1988). Isolation, characterization and evolutionary relatedness of three members from the soybean multigene family
encoding chlorophyll a/b binding proteins. Nucl. Acids Res. 16,
10477-1 0492.
A Homolog of the Substrate Adhesion Molecule Vitronectin Occurs in Four Species of
Flowering Plants.
L. C. Sanders, C. S. Wang, L. L. Walling and E. M. Lord
Plant Cell 1991;3;629-635
DOI 10.1105/tpc.3.6.629
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