BACTERIAL CELLULOSE-BINDING DOMAIN MODULATES IN-VITRO ELONGATION OF DIFFERENT PLANT-CELLS

Recombinant cellulose-binding domain (CBD) derived from the cellulolyt ic bacterium Clostridium cellulovorans was found to modulate the elong ation of different plant cells in vitro. In peach (Prunus persica L.) pollen tubes, maximum elongation was observed at 50 mu g mL(-1) CBD. P ollen tube staining with calcofluor showed a loss of crystallinity in the tip zone of CBD-treated pollen tubes. At low concentrations CBD en hanced elongation of Arabidopsis roots. At high concentrations CBD dra matically inhibited root elongation in a dose-responsive manner. Maxim um effect on root hair elongation was at 100 mu g mL(-1), whereas root elongation was inhibited at that concentration. CBD was found to comp ete with xyloglucan for binding to cellulose when CBD was added first to the cellulose. before the addition of xyloglucan. When Acetobacter xylinum L. was used as a model system, CBD was found to increase the r ate oi cellulose synthase in a dose-responsive manner, up to 5-fold co mpared with the control. Electron microscopy examination of the cellul ose ribbons produced by A. xylinum showed that CBD treatment resulted in a splayed ribbon composed of separate fibrillar subunits, compared with a thin, uniform ribbon in the control.