Abstract
The phytotoxic protein PcF (Phytophthora cactorum-Fragaria) is a 5.6-kDa cysteine-rich, hydroxyproline- containing protein that is secreted in limited amounts by P. cactorum, an oomycete pathogen of tomato, strawberry and other relevant crop plants. Although we have shown that pure PcF triggers plant reactivity, its mechanism of action is not yet understood. Here we show that PcF, like other known fungal protein elicitors involved in pathogen-plant interaction, stimulates the activity of the defense enzyme phenylalanine ammonia a key step in understanding the mechanism of action of PcF at a molecular level is knowledge of its three-dimensional structure, we overexpressed this protein extracellularly in Pichia pastoris. The preliminary structural and functional characterization of a recombinant PcF homologue, N4-rPcF, is reported. Interestingly, although N4-rPcF is devoid of proline hydroxylation and has four additional amino acid residues attached to its N terminus, its secondary structure and biological activity are indistinguishable from wild-type PcF.
Keywords: Phytophthora cactorum, phytotoxic protein, hydroxyproline, circular dichroism, eliciting activity, phenylalanine ammonia lyase activation
Footnotes
Received 22 February 2003; received after revision 25 March 2003; accepted 14 April 2003