A gene encoding a polygalacturonase-inhibiting protein (PGIP) shows developmental regulation and pathogen-induced expression in strawberry

Polygalacturonase-inhibiting proteins (PGIPs) have been demonstrated to play a role in host defence in several plants. The PGIP now cloned from strawberry (Fragaria ananassa) showed a high degree of homology to other fruit PGIPs. The gene expression of strawberry PGIP was monitored in healthy leaves, flowers and fruit at different maturity stages. PGIP transcript levels were also analysed following fruit inoculation with the fungal pathogen Botrytis cinerea in strawberry cultivars displaying variation in susceptibility. Healthy mature berries showed the highest constitutive PGIP gene expression levels compared with leaves, flowers and immature fruit, indicating that the gene is developmentally regulated. Among the cultivars studied ('Elsanta', 'Korona', 'Polka', 'Senga sengana', 'Tenira'), 'Polka' had the highest constitutive expression level of PGIP. After inoculation with B. cinerea, all five cultivars displayed a significant induction of PGIP gene expression, but the differences between them were not statistically significant. The high induction of the PGIP gene after inoculation with B. cinerea indicates that PGIP has a role in defence of strawberr