Infection-related proteins in intercellular washing fluids from stem rust-affected wheat leaves: race-associated protein differences revealed by PAGE and Con A blotting

Abstract

Primary leaves of wheat were infiltrated with buffer and subjected to gentle centrifugation to yield intercellular washing fluid (IWF). Proteins in these fluids were separated by isoelectric focusing-polyacrylamide gel electrophoresis, stained with Coomassie brilliant blue, or first blotted onto nitrocellulose membranes and then probed for concanavalin A (Con A) binding. β- d-Xylosidase isozymes endogenous in IWF served as internal standards for comparison of Con A-binding proteins between samples. Intercellular washing fluid from leaves infected with each of four races of the stem rust fungus contained infection-related proteins. Many of these, including several of the most prominent Con A-binding proteins, differed between the four samples either in amount or in relative mobility. To confirm that these differences were race-associated, leaves were infected with five isolates of one race and similarly analysed. The five isolates had been collected in different years and in widely separated geographic areas to emphasize inter-isolate differences, if they exist. Leaves infected with each of the five isolates yielded indistinguishable patterns of Con A-binding IWF proteins.