THE TOMATO CF-2 DISEASE RESISTANCE LOCUS COMPRISES 2 FUNCTIONAL GENESENCODING LEUCINE-RICH REPEAT PROTEINS

In plants, resistance to pathogens is frequently determined by dominan t resistance genes, whose products are proposed to recognize pathogen- encoded avirulence gene (Avr) products. The tomato resistance locus Cf -2 was isolated by positional cloning and found to contain two almost identical genes, each conferring resistance to isolates of tomato leaf mould (C. fulvum) expressing the corresponding Avr2 gene. The two Cf- 2 genes encode protein products that differ from each other by only th ree amino acids and contain 38 leucine-rich repeat (LRR) motifs. Of th e LRRs, 20 show extremely conserved alternating repeats. The C-terminu s of Cf-2 carries regions of pronounced homology to the protein encode d by the unlinked Cf-9 gene. We suggest that this conserved region int eracts with other proteins involved in activating plant defense mechan isms.