Identification of a partial oil palm polygalacturonase-inhibiting protein (EgPGIP) gene and its expression during basal stem rot infection caused by Ganoderma boninense

Basal stem rot disease (BSR) is a common and serious fungal disease of the oil palm caused by Ganoderma boninense. This fungal disease infects thousands of hectares of plantings in Southeast Asia every year causing not only yield but also tree losses. A natural plant self defence mechanism against fungal infection is the production of fungal resistance protein. A fungal resistance gene that has been reported previously in other monocotyledonous plants such as rice and barley is polygalacturonase-inhibiting protein (PGIP) gene, a plant defence cell wall glycoprotein that has been shown to inhibit the activity of fungal endopolygalacturonase (endo-PGs) and modulate their activity and has the potential to be developed as a disease or resistance biomarker for the oil palm. The identification and isolation of this gene in oil palm allowed for the study of its differential expression during the fungal infection. The oil palm PGIP gene (EgPGIP) has between 60-100% similarities with the database sequence of PGIP from other monocotyledons. Interestingly, we found that the expression of EgPGIP gene measured using Real-Time PCR showed that the expression level of EgPGIP in infected oil palm was temporally down regulated. The results suggest that, down regulation of the EgPGIP is related to the establishment of infection by G. boninense.