CHANGES IN PROTEIN PROFILE OF SUSCEPTIBLE AND RESISTANT SUGAR PINE FOLIAGE INFECTED WITH THE WHITE-PINE BLISTER RUST FUNGUS CRONARTIUM-RIBICOLA

White pine blister rust resistance of sugar pine (Pinus lambertiana) is under major gene (R) control. A detailed analysis of mechanisms underlying such resistance will facilitate the development of a biochemical method for rapid screening for resistant trees based on molecular markers associated with disease resistance. Three and nine days after inoculation of pine seedlings with the blister rust fungus Cronartium ribicola, foliage proteins were extracted and separated by two-dimensional gel electrophoresis. Gels were stained with silver, and proteins were detected and quantified with the aid of a laser-based gel scanner and Sun work-station and 2-D gel software. Gel scans were converted to gel images and then to gel spots by a process of autodetection. From gel spots of all samples collected on a given date, a reference gel was electronically constructed by a process of landmarking, automatic matching, and adding spots. A reference gel usually contained over 2000 proteins. Two acidic proteins (36.7 kDa and 28.1 kDa) were detected in relatively large amounts. The 36.7 kDa protein was significantly suppressed in susceptible seedlings at day 3 while the 28.1 kDa protein was significantly enhanced in resistant seedlings at day 9. In addition, the modulation of a small number of proteins was also shown to be unique to the phenotype (resistance vs. susceptible) of the seedlings. Such proteins are primary candidates for future studies on their role in this host-pathogen interaction.