Expression of active barley seed ribosome-inactivating protein in transgenic wheat

Phenotypically normal, transgenic wheat (Triticum aestivum, var. Frisal) plants expressing a barley seed ribosome-inactivating protein (RIP) were produced. Expression was controlled by an intron-enhanced cauliflower mosaic virus 35S promoter and has been completely stable over four generations so far, possibly due to matrix-associated regions (MARs) that flank the transgenes. An engineered fusion to a signal peptide derived from the barley seed beta-1,3-glucanase caused the transport of RIP to the apoplast. Activity of the accumulated protein could be shown by significant inhibition of a rabbit reticulocyte transcription/translation system. Plants expressing high levels of RIP were protected only moderately or not at all against infection by the fungal pathogen Erysiphe graminis.