Cloning and sequence analysis of a Phytophthora cinnamomi gene which encodes for cinnamomin, a toxin with implications in root rot of cranberry.

Abstract

We used a polymerase chain reaction (PCR) based cloning strategy to isolate cinnamomin genes from Phytophthora cinnamomi 8601, a pathogen responsible for cranberry root rot. Complete DNA sequence analysis of nine recombinant clones revealed two different classes of genes, each class consisting of genes with identical DNA sequences. Both classes of genes (Cin-1 and Cin-2) contained an open reading frame encoding a protein of 122 amino acid residues. The encoded proteins, named cinnamomin-1 and cinnamomin-2 (Cin-1 and Cin-2), were highly homologous to other proteins of the elicitin family and contained a 19 amino acid residue long signal peptide sequence. Both Cin-1 and Cin-2 proteins showed higher degree of sequence homology to the alpha-elicitins than beta-elicitins; moreover, a Val residue was found at position 13 of the putative mature Cin-1 and Cin-2 proteins. Because alpha-elicitins and beta-elicitins are known to contain a Val and a Lys residue, respectively, at this position, we concluded that both Cin-1 and Cin-2 genes from P. cinnamomi 8601 encode for alpha cinnamomins, Cin-1 and Cin-2.