Fungal elicitor triggers rapid, transient, and specific protein phosphorylation in parsley cell suspension cultures

Abstract

Treatment of suspension-cultured parsley (Petroselinum crispum) cells with fungal elicitor triggers rapid, transient and sequential phosphorylation of a number of proteins, as shown by electrophoretic analysis on two-dimensional gels. This response is rapidly reversed by removal of the elicitor from the medium and appears to be specific. It is not observed in cells exposed to other environmental stress factors, such as heat shock, UV irradiation or treatment with mercuric chloride. Pronase digestion of the elicitor has the same negative effect on protein phosphorylation as its previously demonstrated effect on the activation of some pathogen defense-related genes, suggesting a link between these two phenomena. Some of the changes in protein phosphorylation are among the earliest known events following elicitation. The phosphorylation of a neutral 45-kDa protein, which is found in both the microsomal and cytoplasmic fractions, can be observed as early as 1 min after the onset of elicitor treatment. The phosphorylation of a 26-kDa nuclear protein also starts increasing very early. The changes in protein phosphorylation in response to the elicitor are dependent on the presence of Ca2+ in the medium. Our data are compatible with the hypothesis that protein phosphorylation is involved in the signal transduction processes following elicitor recognition by parsley cells.