Effects of boron deficiency in cell suspension cultures of Populus alba L.

Cell suspension cultures of Populus alba L. (original cells) require at least 10 microM boron for appropriate growth. Using original cells we established a cell line, T-5B, which can grow in a medium containing low levels of boron (5 microM). The level of boron localized in the cell walls of T-5B cells was one-half that found in the cell walls of original cells maintained in medium containing 100 microM boron, and the level of the rhamnogalacturonan II dimer, cross-linked by a borate ester, also decreased in the former. The sugar composition of whole cell walls of the T-5B cell line was similar that of the original cells, however pectic polysaccharides composed of arabinose or galacturonic acid were easily extracted from T-5B cell walls with 50 mM trans-1,2-cyclohexanediamine-N,N,N',N'-tetraacetic acid. Our results suggest that boron deficiency causes a weakening of the interaction among pectic polysaccharides due to a decrease in boron-rhamnogalacturonanII cross-linkage.