The fungal elicitor cryptogein induces cell wall modifications on tobacco cell suspension

Upon addition of the fungal elicitor cryptogein, suspension cells of tobacc o (Nicotiana tabacum cv. Xanthi) aggregated in clusters. Cytochemical exper iments indicated that elicited cells displayed fibrillar expansions of pect in along the primary cell wall. Immunocytochemical detection of pectin epit opes indicated that the fibrillar material surrounding the treated cells wa s mostly composed of low methylated galacturonan sequences, but the use of the cationic probe did not reveal the presence of negatively charged carbox yl groups: the presence of important amounts of calcium ions in these pecti c fibrillar expansions accounts for these observations. These data indicate that tobacco cells treated with cryptogein show a cell wall altered by the presence of a calcium pectate gel, resulting from the reorganization of pe ctin in the middle lamellae. These results are consistent with a drastic re duction in wall digestibility, partially reversed by increasing the pectoly ase concentration in the hydrolytic solution. Diphenylene iodonium, an inhi bitor of the oxidative burst triggered by cryptogein on tobacco cells, part ially prevents elicited cell walls from this loss of digestibility, suggest ing a possible role of active oxygen species in the cell wall strengthening . This work represents a new element of the signal transduction cascade tri ggered on tobacco cells by cryptogein.