PLANT NUCLEAR-PROTEIN P56 AND ITS ELICITOR-DEPENDENT TRANSIENT BIOSYNTHESIS

Pulse labelling experiments with [S-35]L-methionine were performed to determine the rate of protein synthesis. Treatment of cultured cells o f peanut with fungal cell wall led to a drastic increase in the de nov o synthesis of particular proteins in the cytosol, the endoplasmic ret iculum and the extracellular compartment. In the nucleus, a single new ly synthesized protein, designated p 56, was detectable upon elicitati on by fungal elicitor. Pulse labelling with [S-35]L-methionine for 1 h was applied at various times following elicitation. The time course o f p 56 biosynthesis was transient and the maximum of p 56 de novo synt hesis preceded the one of the cytosolic protein stilbene synthase. The preferential de novo synthesis and transfer of p 56 to the nucleus, o nly briefly before the elicitor-triggered signal chain causes the acti vation of nuclear defence genes, makes it a good candidate as member o f the signal transduction machinery to the nucleus. p 56 was further c haracterized by its size as N-octyl-beta-D-glucoside micelle. Selectiv e solubilization experiments showed that p 56 is a hydrophobic, not sa lt extractable protein rather well protected against partial proteolys is.