PLANT PHYSIOLOGY , Vol 113, Issue 4 1071-1080, Copyright © 1997 by American Society of Plant Biologists
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BIOCHEMISTRY AND ENZYMOLOGY |
Extracellular Matrix Assembly in Diatoms (Bacillariophyceae) (II. 2,6-Dichlorobenzonitrile Inhibition of Motility and Stalk Production in the Marine Diatom Achnanthes longipes)
Y. Wang, J. Lu, J. C. Mollet, M. R. Gretz and K. D. Hoagland
Department of Biological Sciences, Michigan Technological University, Houghton, Michigan 49931-1295 (Y.W., J.L., J.-C.M., M.R.G.)
The cellulose synthesis inhibitor 2,6-dichlorobenzonitrile (DCB) and the
DCB analogs 2-chloro-6-fluorobenzonitrile,
3-amino-2,6-dichlorobenzonitrile, and
5-dimethylamino-naphthalene-1-sulfonyl-(3-cyano-2, 4-dichloro)aniline
(DCBF) inhibited extracellular adhesive production in the marine diatom
Achnanthes longipes, resulting in a loss of motility and a lack of
permanent adhesion. The effect was fully reversible upon removal of the
inhibitor, and cell growth was not affected at concentrations of inhibitors
adequate to effectively interrupt the adhesion sequence. Video microscopy
revealed that the adhesion sequence was mediated by the export and assembly
of polymers, and consisted of initial attachment followed by cell motility
and eventual production of permanent adhesive structures in the form of
stalks that elevated the diatom above the substratum. A. longipes adhesive
polymers are primarily composed of noncellulosic polysaccharides (B.A.
Wustman, M.R. Gretz, and K.D. Hoagland [1997] Plant Physiol 113:
1059-1069). These results, together with the discovery of DCB inhibition of
extracellular matrix assembly in noncellulosic red algal unicells (S.M.
Arad, O. Dubinsky, and B. Simon [1994] Phycologia 33: 158-162), indicate
that DCB inhibits synthesis of noncellulosic extracellular polysaccharides.
A fluorescent probe, DCBF, was synthesized and shown to inhibit adhesive
polymer production in the same manner as DCB. DCBF specifically labeled an
18-kD polypeptide isolated from a membrane fraction. Inhibition of adhesion
by DCB and its analogs provides evidence of a direct relationship between
polysaccharide synthesis and motility and permanent adhesion.
