A NEW ELICITOR OF THE HYPERSENSITIVE RESPONSE IN TOBACCO - A FUNGAL GLYCOPROTEIN ELICITS CELL-DEATH, EXPRESSION OF DEFENSE GENES, PRODUCTION OF SALICYLIC-ACID, AND INDUCTION OF SYSTEMIC ACQUIRED-RESISTANCE

A 32 kDa glycoprotein whose effects in tobacco and other Nicotianae mi mic a typical hypersensitive response, was isolated from Phytophthora megasperma. Infiltration of a few nanograms of the protein into leaves caused the formation of lesions that closely resemble hypersensitive response lesions. Transcripts of genes encoding enzymes of the phenylp ropanoid and sesquiterpenoid pathways accumulated rapidly after elicit or application followed by salicylic acid production. Cellular damage, restricted to the infiltrated zone, occurred only several hours later , at a time when expression of PR protein genes was activated. After s everal days systemic acquired resistance was also induced. Thus, tobac co plant cells that perceived the glycoprotein generated a cascade of signals acting at local, short, and long distances, and causing the co ordinate expression of specific defence responses in a way similar to hypersensitivity to tobacco mosaic virus. The glycoprotein represents a powerful tool to investigate further the signals and their transduct ion pathways involved in induced disease resistance. It may also be us eful to engineer broad disease protection in a Nicotianae and possibly into crop plant species.