Comparison of the effects of cryptogein and oligogalacturonides on tobacco cells and evidence of different forms of desensitization induced by these elicitors

The effects of cryptogein and oligogalacturonides (OGs) were compared on tobacco cells by measuring calcium influx and calcium-dependent responses including extracellular alkalinization and H2O2 production. The main difference is the higher calcium influx and the sustained H2O2 production induced by cryptogein compared to OGs. Amplitude and duration 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 cells treated with OGs or cryptogein differed in their ability to respond to a subsequent stimulation: OGs-treated cells were refractory to the same stimulus but remained responsive to cryptogein whereas cryptogein-treated cells still responded weakly to a second application of cryptogein or OGs. Desensitization induced by OGs and cryptogein could correspond, respectively, to some forms of homologous or heterologous desensitization described in animal systems. Alternatively, cryptogein-activated pathways via large calcium influx could promote important cellular modifications leading to a reduction of response in general. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.