Figure 1.

BTH-Induced Protease Activities in the Tomato Apoplast.

(A) Apoplastic PR accumulation in BTH-treated tomato plants. Five-week-old tomato plants were treated with water or BTH. AFs were isolated after 5 d, and equal volumes were separated on a 17% protein gel to visualize PR protein accumulation in the AF.

(B) Protease activity profiling on equal volumes of total extract and AF of combined leaves from water- or BTH-treated tomato plants. Extracts were labeled at pH 5.0 with DCG-04 in the absence or presence of an excess of E-64. Proteins were separated on 12% protein gels, and biotinylated proteins were detected on a protein blot with streptavidin-HRP. Total extracts corresponds to ∼0.17 cm² leaf area/lane; AF corresponds to ∼7.4 cm² leaf area/lane. A representative of seven independent experiments is shown. An enlarged Coomassie blue–stained gel (cbb) shows equal loading and the accumulation of PR3 proteins.

(C) Protease activity profiling of AFs from young leaves of water- and BTH-treated tomato plants. A Coomassie blue–stained gel (cbb) shows equal loading and the accumulation of PR3 proteins.

(D) Protease activity profiling on AFs isolated from leaves of different age of the same water-treated plant (indicated in illustration on the right). E-64 competition was incomplete, resulting in some remaining 25-kD signal.