cDNA cloning and expression of polygalacturonase-inhibiting proteins (PGIPs) from red raspberry (Rubus idaeus)

Plant polygalacturonase-inhibiting proteins (PGIPs) inhibit endo-polygalacturonases (endo-PGs) released by invasive fungi. Two potential PGIP cDNAs have been cloned from raspberry (Rubus idaeus). PGIP1 corresponds to a full-length PGIP cDNA with a high degree of identity with previously isolated genes and maintains all the characteristic features of PGIP peptides. A genomic fragment of PGIP1 identifies a single 243 bp intron which is efficiently spliced out of the PGIP1 pre-mRNA transcript. PGIP2 contains a frame shift mutation which would lead to the loss of 105 amino acids off the C-terminus. Contrary to PGIP activity levels in raspberry (Johnston et el., 1993), expression analysis detected PGIP1 at equal levels throughout fruit development from closed flower, through to ripe fruit.