|De lorenzo, Giulia|
Submitted to: Molecular Plant-Microbe Interactions
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/20/2007
Publication Date: 2/1/2008
Citation: Janni, M., Sella, L., Favaron, F., Blechl, A.E., De Lorenzo, G., D'Ovidio, R. 2008. The expression of a bean pgip in transgenic wheat confers increased resistance to the fungal pathogen bipolaris sorokiniana. Molecular Plant-Microbe Interactions.21:171-177. Interpretive Summary: Fungal pathogens that infect plants make enzymes, such as polygalacturonase (PG), that degrade plant cell walls. One of the plant’s defense mechanisms is production of inhibitors of these enzymes, such as polygalacturonase-inhibitory proteins (PGIPs). In order to improve its resistance to fungal pathogens, we transformed wheat with a gene from green beans that encodes a PGIP that has been shown to inhibit the PG enzymes of many different fungi. We studied the characteristics of three different transgenic wheat lines that accumulated the bean PGIP. We found that the bean PGIP was correctly routed to the space outside wheat cells. Wheat tissues containing the bean PGIP were more resistant to digestion by PG enzymes from a Fusarium fungus than non-transformed wheat tissues. The transgenic wheat plants had only half the symptoms of non-transformed plants 72 hours after infection with spores of the fungus that causes foliar spot blotch (Bipolaris sorokiniana). Our results illustrate the feasibility of improving wheat’s defenses against pathogens by expression of proteins with new capabilities to counteract those produced by infecting fungi.
Technical Abstract: A possible strategy to control plant pathogens is the improvement of natural plant defense mechanisms against the tools that pathogens commonly use to penetrate and colonize the host tissue. One of these mechanisms is represented by the host plant’s ability to inhibit the pathogen’s capacity to degrade plant cell wall polysaccarides. Polygalacturonase-inhibiting proteins (PGIPs) are plant defense cell wall glycoproteins that inhibit the activity of fungal endopolygalacturonases (endo-PGs). To assess the effectiveness of these proteins in protecting wheat from fungal pathogens, we produced a number of transgenic wheat lines expressing a bean PGIP (PvPGIP2) having a wide spectrum of specificities against fungal PGs. Three independent transgenic lines were characterized in detail, including determination of the levels of PvPGIP2 accumulation, its sub-cellular localization and inhibitory activity. Results show that the transgene-encoded protein is correctly secreted into the apoplast, maintains its characteristic recognition specificities, and endows the transgenic wheat with new PG recognition capabilities. As a consequence, transgenic wheat tissue showed increased resistance to digestion by the PG of Fusarium moniliforme. These new properties were also confirmed at the plant level during interactions with the fungal pathogen Bipolaris sorokiniana. All three lines showed significant reductions in symptom progression (46%-50%) through the leaves following infection with this pathogen. Our results illustrate the feasibility of improving wheat’s defenses against pathogens by expression of proteins with new capabilities to counteract those produced by the pathogens.