Figure 4.

The N-terminal transit sequence of MKK4 is required both for import and for activation of downstream MAPKs and associated cell death. (A) Radiolabelled ΔN65CA-MKK4 and Heterosigma PsbO precursors were incubated with intact pea chloroplasts. After incubation, samples were treated with trypsin, re-isolated, washed, lysed, fractionated and analyzed by SDS-PAGE, followed by autoradiography. Translation products (lanes T); washed chloroplast fraction (lanes C-); protease-treated chloroplast fraction (lanes C+). (B) Localized cell death induced by transient expression of CA-MKK4 and ΔN65CA-MKK4 in tobacco. (C) Downstream activation of SIPK and WIPK as detected by anti-pERK immunoblotting.