Molecular relatedness of the polygalacturonase-inhibiting protein genes inEucalyptus species

Plants produce polygalacturonase-inhibiting proteins (PGIPs) as part of the ir defense against disease. PGIPs have leucine-rich motifs, a characteristi c shared by many proteins involved in plant resistance against pathogens. T he objective of this study was to clone and analyse the partial sequences o f the pgip genes from five selected commercially important Eucalyptus speci es. Genomic DNA from E. grandis, E, urophylla, E. camaldulensis, E, nitens and E, saligna was isolated from young leaves and used as the template in P CR reactions. Primers PC1, previously described, and Per3, developed in thi s study, were used in a degenerate PCR reaction to amplify a pgip fragment. A PCR fragment of 909 bp was amplified from each Eucalyptus spp., cloned a nd sequenced. The Eucalyptus pgip genes were highly conserved (98-100% iden tity). Analysis of the deduced amino-acid sequences revealed high similarit ies (44-94%) with other known PGIPs. In general, PGIPs have high homologies within genera as is the case in the genus Citrus. These observations stren gthen the belief that PGIP plays an important role in plants.