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-dichlo rbenzonitirle (DCB) increased the pectin content by 31 and 86%, respectivel y. 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 content s 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 formatio n as an indicator of Al injury was closely positively correlated to the los s of cell viability. In NaCl-adapted and pectolyase-treated cells, Al-induc ed callose formation was reduced when compared with normal cells. However, there was a close positive relationship between pectin contents and relativ e callose induction (digitonin-induced callose formation, reflecting the di fferent 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-m atrix represents an important step in the expression of Al toxicity.