PECTIC SIGNAL-TRANSDUCTION IN CARROT CELLS - MEMBRANE, CYTOSOLIC AND NUCLEAR RESPONSES INDUCED BY OLIGOGALACTURONIDES

Oligogalacturonides were applied at a concentration of 0.2 mg ml(-1) t o Daucus carota cells and protoplasts. Fractions containing oligomers of degree of polymerisation 9 to 16 in the presence of 150 mM NaCl and 0.5 mM CaCl2, and pure oligomers of degree of polymerisation 9 to 13 in the same ionic medium, triggered a cytosolic calcium mobilisation, membrane depolarisation and cytosolic acidification. These membrane an d cytosolic events coincided with the accumulation of transcripts enco ding phenylalanine ammonia-lyase, catalytic activitation of the enzyme and p-hydroxybenzoic acid accumulation in the cell wall of the elicit ed cells. The effect of a calcium ionophore, calcium channel blockers, calmodulin inhibitors, phosphatidyl inositol metabolism modulators an d H+-ATPase modulators were investigated on oligogalacturonide-induced phenylalanine ammonia-lyase enzyme and gene activation in suspension- cultured carrot cells.