Signal transduction in higher plants in response to a pathogen attack : Identification of membrane, cytosolic and nuclear responses induced by oligogalacturonides.
This study reports the effects of pectic fragments on defense respponses in suspension-cultured carrot cells. Pectic fragments trigger several cytosolic (cytosolic free calcium mobilisation and cytosolic acidification) and nuclear responses (defense gene activation). These response were dependent on the size and conformation of the pectic fragments. Using a pharmalogical approach, we showed that G proteins are involved in signal transduction. Cytosolic free calcium mobilisation is mediated by the opening of calcium channels and the activation of the phosphotidylinositol pathway. This increase in cytosolic free calcium triggered a membrane depolarization (through the inhibition on the proton pump), followed by a cytosotic acidification. These cytosolic responses are believed to activate and modulate serveral kinases.