Specific polyclonal antibodies for the obligate plant parasite Polymyxa - a targeted recombinant DNA approach

Highly specific rabbit polyclonal antibodies for the obligate sugar-beet ro ot parasite, Polymyxa betae, were produced using a novel recombinant DNA ap proach. Parasite cDNA was selectively isolated from infected roots, express ed in vitro, and the purified protein used to raise antibodies. This produc ed clean, precisely targeted antibodies, and allowed for rigorous screening of candidate genes and their products at the molecular level prior to anim al immunization. This approach selects for genes whose products are highly expressed by the parasite in planta, and five such candidate genes from Pol ymyxa betae were identified and cloned. Polyclonal antiserum developed usin g the product of one such gene was found to react specifically with P. beta e in sugar-beet roots and with the closely related Polymyxa graminis in bar ley roots, and to cross-react with Plasmodiophora brassicae in cabbage root s, without the need for further purification. No cross-reaction was detecte d with protein extracts from potato roots infected by the plasmodiophoromyc ete Spongospora subterranea. In all cases, there was no interaction with pr oteins from host plants, or from other microorganisms found in association with uninoculated sugar-beet, barley, cabbage and potato roots.