Bean Polygalacturonase-Inhibiting Protein Expressed in Transgenic Sugar Beet Inhibits Polygalacturonase from Rhizoctonia Solani

M. Kalantari, M. Motallebi* and M. R. Zamani

National Institute of Genetic Engineering and Biotechnology (NIGEB), Tehran, I.R. of Iran

ABSTRACT: Polygalacturonase-inhibiting proteins (PGIPs) selectively inhibit the polygalacturonases (PGs) secreted by the invading plant pathogenic fungi. The PGIPs display the differential inhibiting towards the PGs from different fungi, also towards the different isoforms of the PGs originating from the specific pathogen. In this study the extracts from the Phaseolus vulgaris (cv. Emerson) hypocotyle inhibited the crude protein containing the cell wall degrading polygalacturonase activity of Rhizoctonia solani AG2-2, the causal agent of the root and stem rot on the sugar beet. This inhibitory activity has not yet been linked conclusively to the activity of the pgip2 gene product. In this study, after isolation and cloning of the pgip2 gene from bean, we used a transgenic over-expression approach to show that the PGIP encoded by the pgip2 gene is active against the PGs of R. solani. To assess the effectiveness of these proteins in protecting the sugar beet from the fungal pathogens, a number of the transgenic sugar beet lines expressing a bean pgip2 were produced. Independent transgenic lines were characterized by PCR, southern dot blot, agarose diffusion assay and ELISA. The presented data confirm the antifungal nature of the pgip2 gene.

KEYWORDS: pgip2; sugar beet; Rhizoctonia solani; PGIP; polygalacturonase

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