The Boron Requirement and Cell Wall Properties of Growing and Stationary Suspension-CulturedChenopodium album L. Cells1

Abstract

Suspension-cultured Chenopodium album L. cells are capable of continuous, long-term growth on a boron-deficient medium. Compared with cultures grown with boron, these cultures contained more enlarged and detached cells, had increased turbidity due to the rupture of a small number of cells, and contained cells with an increased cell wall pore size. These characteristics were reversed by the addition of boric acid (>7 M) to the boron-deficient cells. C. album cells grown in the presence of 100 M boric acid entered the stationary phase when they were not subcultured, and remained viable for at least 3 weeks. The transition from the growth phase to the stationary phase was accompanied by a decrease in the wall pore size. Cells grown without boric acid or with 7 M boric acid were not able to reduce their wall pore size at the transition to the stationary phase. These cells could not be kept viable in the stationary phase, because they continued to expand and died as a result of wall rupture. The addition of 100 M boric acid prevented wall rupture and the wall pore size was reduced to normal values. We conclude that boron is required to maintain the normal pore structure of the wall matrix and to mechanically stabilize the wall at growth termination.The ultrastructure and physical properties of plant cell walls are known to be affected by boron deficiency (Kouchi and Kumazawa, 1976; Hirsch and Torrey, 1980; Fischer and Hecht-Buchholz, 1985; Matoh et al., 1992; Hu and Brown, 1994; Findeklee and Goldbach, 1996). Moreover, boron is predominantly localized in the cell wall when plants are grown with suboptimal boron (Loomis and Durst, 1991; Matoh et al., 1992; Hu and Brown, 1994; Hu et al., 1996). In radish, Ͼ80% of the cell wall boron is present in the pectic polysaccharide RG-II (Matoh et al., 1993; Kobayashi et al., 1996), which is now known to exist as a dimer that is cross-linked by a borate ester between two apiosyl residues (Kobayashi et al., 1996; O'Neill et al., 1996). Dimeric RG-II is unusually stable at low pH and is present in a large number of plant species (Ishii and Matsunaga, 1996; Kobayashi et al., 1996 Kobayashi et al., , 1997 Matoh et al., 1996; O'Neill et al., 1996; Pellerin et al., 1996; Kaneko et al., 1997). The widespread occurrence and conserved structure of RG-II (Darvill et al., 1978; O'Neill et al., 1990) have led to the suggestion that borate ester cross-linked RG-II is required for the development of a normal cell wall (O'Neill et al., 1996; Matoh, 1997).One approach for determining the function of boron in plant cell walls is to compare the responses to boron deficiency of growing plant cells that are dividing and synthesizing primary cell walls with those of growth-limited plant cells in which the synthesis of primary cell walls is negligible. Suspension-cultured cells are well suited for this purpose because they may be reversibly transferred from a growth phase to a stationary phase. Continuous cell growth phase is maintained by frequent transfer of the cells into new growth medium...

Use of Phenylboronic Acids to Investigate Boron Function in Plants. Possible Role of Boron in Transvacuolar Cytoplasmic Strands and Cell-to-Wall Adhesion

“…Application of PBA to bean caused root elongation even in the presence of boron and was used to propose that boron acting as a diester cross-linker has two effects on plant growth, both promoting root elongation and simultaneously stabilizing the cell wall and thereby inhibiting excessive elongation (Odhnoff, 1961). The latter is supported by Fleischer et al (1998), who showed that omission of boron from cultured Chenopodium cells in the stationary phase caused the cells to continue to expand and rupture. These data suggest that the stabilizing function of boron could be disrupted by boronic acids, which form monoester linkages and cannot replace the requirement for borate diester cross-links.…”

TheArabidopsisRoot Hair Cell Wall Formation Mutantlrx1Is Suppressed by Mutations in theRHM1Gene Encoding a UDP-L-Rhamnose Synthase

“…In future experiments, it will be useful to investigate whether the rol1 and lrx1 mutants change the pectin structure of root hairs and whether, for example, pore sizes might be affected in these lines. A method to measure porosity of pectin has been established for Chenopodium album (Fleischer et al, 1998) and can most likely be adapted for Arabidopsis to investigate this point. In a complementary approach, Fourier transform infrared spectroscopy (McCann and Carpita, 2005) might reveal changes in the molecular structure of cell walls of the different mutants.…”

The Gene Expression and Enzyme Activity of Plant 3-Deoxy-D-Manno-2-Octulosonic Acid-8-Phosphate Synthase Are Preferentially Associated with Cell Division in a Cell Cycle-Dependent Manner

“…RG-II is the only known boratebinding polysaccharide in the primary cell wall, sequestering up to 80% of the cellular boron (B; Matoh et al, 1996). B deficiency results in altered plant growth and changes in cell wall architecture (Fleischer et al, 1998(Fleischer et al, , 1999Ishii et al, 2001). Thus, B-mediated cross-linking of RG-II generates a covalently crosslinked pectic network that is involved in the regulation of cell wall properties and plant growth (Fleischer et al, 1999;Ishii et al, 1999Ishii et al, , 2001.…”