PLANT PHYSIOLOGY , Vol 104, Issue 1 147-152, Copyright © 1994 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Involvement of Phenolic Esters in Cell Aggregation of Suspension-Cultured Rice Cells
Y. Kato, H. Yamanouchi, K. Hinata, C. Ohsumi and T. Hayashi
Department of Education, Hirosaki University, Hirosaki 036, Japan (Y.K.)
Fluorescence microscopy of rice (Oryza sativa L.) callus sections showed
that all of the walls fluoresced blue in water (pH 5.8) and green in
ammonia (pH 10.0), both characteristics of feruloyl esters. Such
fluorescence in the walls of cells cultured in Gamborg's B5 medium was much
stronger than that in amino acid (AA) medium. Laser scanning microscopy
showed that the level of fluorescence was higher in the intercellular
layer, especially at corner junctions between cells, suggesting that
ferulic acid ester derivatives are located in the middle lamella as well as
in the wall. Extracellular polysaccharides appearing during cultivation in
AA medium were more highly feruloylated than those in B5 medium during
cultivation. Both the levels of ferulic and diferulic acid and the relative
proportion of diferulic acid in the walls of cells increased on transfer of
the cells cultured in AA medium to B5 medium. The walls of cells cultured
in B5 medium maintained constant levels and proportions of the phenolic
acids. Removal of phenolic acids from wall preparations by carboxylesterase
facilitated the solubilization of noncellulosic polysaccharides. Treatment
of the cell aggregates grown in AA medium with an enzyme that hydrolyzes
feruloyl esters decreased the size of the aggregates to between 20 and 500
[mu]m, compared with an original size between 200 and 1000 [mu]m. These
findings suggest that feruloyl and diferuloyl esters between
polysaccharides are involved in the aggregation of cultured rice cells.
