Extracellular Matrix Assembly in Diatoms
(Bacillariophyceae)1
III. Organization of Fucoglucuronogalactans within the Adhesive
Stalks of Achnanthes longipes
Brandon A. Wustman,
Jan Lind,
Richard Wetherbee, and
Michael R. Gretz*
Department of Biological Sciences, Michigan Technological
University, Houghton, Michigan 49931-1295 (B.A.W., M.R.G.); and School
of Botany, University of Melbourne, Parkville, Victoria 3052, Australia
(J.L., R.W.)
Achnanthes longipes is
a marine, biofouling diatom that adheres to surfaces via adhesive
polymers extruded during motility or organized into structures called
stalks that contain three distinct regions: the pad, shaft, and collar.
Four monoclonal antibodies (AL.C1-AL.C4) and antibodies from two
uncloned hybridomas (AL.E1 and AL.E2) were raised against the
extracellular adhesives of A. longipes. Antibodies
were screened against a
hot-water-insoluble/hot-bicarbonate-soluble-fraction. The
hot-water-insoluble/hot-bicarbonate-soluble fraction was fractionated to yield polymers in three size ranges: F1, 
20,000,000 Mr; F2, 
100,000
Mr; and F3, <10,000
Mr relative to dextran standards. The
100,000-Mr fraction consisted of highly
sulfated (approximately 11%) fucoglucuronogalactans (FGGs) and
low-sulfate (approximately 2%) FGGs, whereas F1 was
composed of O-linked FGG (F2)-polypeptide (F3) complexes. AL.C1, AL.C2, AL.C4, AL.E1, and AL.E2
recognized carbohydrate complementary regions on FGGs, with
antigenicity dependent on fucosyl-containing side chains. AL.C3 was
unique in that it had a lower affinity for FGGs and did not label any portion of the shaft. Enzyme-linked immunosorbent assay and
immunocytochemistry indicated that low-sulfate FGGs are expelled from
pores surrounding the raphe terminus, creating the cylindrical outer
layers of the shaft, and that highly sulfated FGGs are extruded from
the raphe, forming the central core. Antibody-labeling patterns and
other evidence indicated that the shaft central-core region is related to material exuded from the raphe during cell motility.
1
This research was supported by the Office of
Naval Research (grant nos. N00014-94-1-0273 and N00014-94-1-0766) to
M.R.G and Kyle D. Hoagland and a Michigan Technological University
Fellowship Award to B.A.W.
*
Corresponding author; e-mail mrgretz{at}mtu.edu; fax
1-906-487-3167.
Plant Physiol. (1998) 116: 1431-1441
Copyright Clearance Center: 0032-0889/98/116/1431/11
© 1998 American Society of Plant Physiologists
