Expression of pokeweed antiviral proteins in creeping bentgrass

Fungal diseases of creeping bentgrass, an important amenity grass used extensively on golf courses, are a serious problem in golf course management. Transgenic approaches to improving disease resistance to fungal diseases are being explored in many species, and in some cases ribosome-inactivating proteins have been found to be effective. We have generated transgenic creeping bentgrass plants expressing three forms of ribosome-inactivating proteins from pokeweed, which are termed pokeweed antiviral proteins (PAP). PAP-Y and PAP-C are nontoxic mutants of PAP; PAPII is the native form of another ribosome-inactivating protein from pokeweed. In creeping bentgrass, PAP-C transformants did not accumulate the protein, suggesting that it is unstable, and in a field test these plants were not protected from infection by the fungal pathogen Sclerotinia homoeocarpa, the causal agent of dollar spot disease. PAPII transformants could accumulate stable levels of the protein but had symptoms of toxicity; one low-expressing line exhibited good disease resistance. PAP-Y transformants accumulated stable levels of protein, and under greenhouse conditions they appeared to be phenotypically normal.