Receptor-mediated increase in cytoplasmic free calcium required for activation of pathogen defense in parsley

Receptor-mediated increase in cytoplasmic free calcium required for activation of pathogen defense in parsley

2000

A:PS

Transient influx of Ca2+ constitutes an early element of signalling cascades triggering pathogen defence responses in plant cells. Treatment with the Phytophthora sojae-derived oligopeptide elicitor, Pep-13, of genetically transformed parsley cells stably expressing the gene for apoaequorin (used to quantify changes in [Ca2+]cyt) revealed a rapid increase in cytoplasmic free calcium ([Ca2+]cyt), which peaked at ? æM and subsequently declined to sustained values of 300 nM. Activation of this biphasic [Ca2+]cyt signature was achieved by elicitor concentrations sufficient to stimulate Ca2+ influx across the plasma membrane, oxidative burst, and phytoalexin production. Sustained [Ca2+]cyt but not the rapidly induced [Ca2+]cyt transient peak are required for activation of defence-associated responses. Modulation by pharmacological effectors of Ca2+ influx across the plasma membrane or of Ca2+ release from internal stores suggests that the elicitor-induced sustained increase of [Ca2+]cyt predominantly results from the influx of extracellular Ca2+. Identical structural features of Pep-13 were found to be essential for receptor binding, increases in [Ca2+]cyt, and activation ofdefence-associated responses. Thus, a receptor-mediated increase in [Ca2+]cyt is causally involved in signalling the activation of pathogen defence in parsley.

v.12(8):1425-1440, PLANT CELL

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