Cell wall pectin content modulates aluminium sensitivity of Zea mays (L.) cells grown in suspension culture

The pectin content of the cell walls of maize suspension cells was modified to investigate its role in the expression of aluminium (Al) toxicity. Long-term adaptation to NaCl or to the cellulose synthesis inhibitor 2,6-dichlorbenzonitirle (DCB) increased the pectin content by 31 and 86%, respectively. Subculturing salt-adapted cells for up to 3 weeks without NaCl supply or treatment of cells with pectolyase for up to 15 min reduced pectin contents by up to 46%. Such pre-cultured cells were incubated for 2 h in presence of Al. There was a close positive correlation between pectin and both total and BaCl2 non-exchangeable Al contents. Aluminium-induced callose formation as an indicator of Al injury was closely positively correlated to the loss of cell viability. In NaCl-adapted and pectolyase-treated cells, Al-induced callose formation was reduced when compared with normal cells. However, there was a close positive relationship between pectin contents and relative callose induction (digitonin-induced callose formation, reflecting the different capabilities of cells to synthesize callose set to 100%) indicating that cells with higher pectin contents are more Al-sensitive. The results presented support our view that the binding of Al to the cell wall pectin-matrix represents an important step in the expression of Al toxicity.