Figure 6.

Activity-Based Protein Profiling Shows Activation of Maize Cys Proteases by SA.

(A) Immunoblot detection of DCG-04-labeled protein extracts from maize leaf extracts taken 2 d after infection with U. maydis strain SG200 compared with control samples taken 2 d after buffer (mock) treatment. Extracts were either untreated or pretreated with 5 μM E-64. LC, loading control.

(B) DCG-04 labeling of leaf extract from seedlings 2 d after treatment with 2 mM SA or buffer (mock). Extracts were pretreated with 5 μM E-64, 0.5 μM CC9, 0.5 μM CC9^ia, or untreated, and subsequently labeled with DCG-04.

(C) DCG-04 labeling of protein extract from maize seedling leaves of two cc9-overexpressing lines (CC9^oe4/8 and CC9^oe4/11) and similar leaves of HiII wild-type plants as control. Leaves were taken 2 d after treatment with 2 mM SA or buffer (mock). Extracts were pretreated with 5 μM E-64 (+) or untreated (−), and subsequently labeled with DCG-04. Biotinylated proteases were detected using strep-HRP.

[See online article for color version of this figure.]