COMPARISON OF THE EFFECTS OF CRYPTOGEIN AND OLIGOGALACTURONIDES ON TOBACCO CELLS AND EVIDENCE OF DIFFERENT FORMS OF DESENSITIZATION INDUCEDBY THESE ELICITORS

The effects of cryptogein and oligogalacturonides (OGs) were compared on tobacco cells by measuring calcium influx and calcium-dependent res ponses including extracellular alkalinization and H2O2 production. The main difference is the higher calcium influx and the sustained H2O2 p roduction induced by cryptogein compared to OGs. Amplitude and duratio n of calcium signalling triggered by cryptogein or OGs may explain the necrotic effect of cryptogein, and the absence of necrosis in tobacco plants treated with OGs. We used induction of alkalinization and H2O2 production to investigate cryptogein effects after a first treatment with cryptogein or OGs, and reciprocally. Results show that tobacco ce lls treated with OGs or cryptogein differed in their ability to respon d to a subsequent stimulation: OGs-treated cells were refractory to th e same stimulus but remained responsive to cryptogein whereas cryptoge in-treated cells still responded weakly to a second application of cry ptogein or OGs. Desensitization induced by OGs and cryptogein could co rrespond, respectively, to some forms of homologous or heterologous de sensitization described in animal systems. Alternatively, cryptogein-a ctivated pathways via large calcium influx could promote important cel lular modifications leading to a reduction of response in general. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.