Differential accumulation of proteins in resistant and susceptible sugar pine (Pinus lambertiana) seedlings inoculated with the white pine blister rust fungus (Cronartium ribicola)

Foliar and stem proteins from 21 resistant and 21 susceptible sugar pine seedlings inoculated with Cronartium ribicola were resolved on SDS-PAGE and two-dimensional gel electrophoresis. The protein profiles of pooled and individual samples were analyzed. SDS-PAGE analysis showed the presence of a 19-kDa protein band in infected susceptible foliage. Partial N-terminal amino acid sequence analysis revealed that this band was a mixture of histone and a Cro r I protein. The Cro r I protein was fungus- derived, while the origin of histone was not clear. Utilizing fungal-specific monoclonal antibodies, we determined that about 90% of susceptible seedlings had fungal antigens, while only one resistant seedling showed the presence of fungal antigens. This illustrated the potential use of these monoclonal antibodies as probes in screening seedlings for susceptibility. In addition, significantly greater amounts of seasonally regulated Pin I I protein was found in the foliage of resistant versus susceptible seedling...