Regulation of cell-wall polysaccharide components by CaCl₂ in suspension cultures of kidney bean (<i>Phaseolus vulgaris</i>)

We cultured the suspension cells of kidney bean in MS media supplemented with one of five concentrations of CaCI 2 [0,22,44 (control), 88, or 176 mg/L], and harvested them at the logistic (15 d) and early-stationary (30 d) phases. Cells grown at concentrations higher than 22 mg/L showed better proliferation than those at 0 mg/L The rate of proliferation also increased with higher concentrations. We fractionated the individual sugars into symplastic (EtOH and starch) and apoplastic (low-molecular pectin, high-molecular pectin, hemicellulose, and cellulose) components. Cells treated at the highest concentration (176 mg/L) exhibited the greatest amount of sugar in the EtOH and starch fraction during the logistic phase. In contrast, cells in the early stationary phase had the highest level of sugar at treatment concentrations of less than 22 mg/L. For treatment concentrations higher than 22 mg/L on Day 15, more pectin and hemicellulose was detected at greater amounts compared with those cells treated with 0 mg/L. However, at Day 30, concentrations higher than 44 mg/L induced greater amounts of pectin and hemicellulose than from the other concentrations. Cellulose was more abundant with the 0 mg/L treatment, and contents ranged from 17.4 to 25.5% in the primary cell walls over all treatment concentrations. These results indicate that CaCI 2 modulates both symplastic and apoplastic sugar metabolism. Therefore, we suggest that the cell-wall structure may define the mode of polysaccharide biosynthesis during cell growth.