Expression of DIR1-GUS or DIR1Δ1-25-GUS rescues the SAR defect in dir1-1. SAR assays were conducted on Ws, dir1-1, DIR1pro:DIR1-GUS-29/dir1-1 and 35S: DIR1Δ1-25-GUS-5/dir1-1 by inoculating with 10 mM MgCl2 (mock-induced) or inducing for SAR with Pst-avrRpt2 (SAR-induced) in 1 to 2 lower leaves, followed by challenge inoculation with virulent Pst in distant leaves 2 days later. Bacterial density determination was performed in challenged leaves 3 dpi. Asterisks (*) denote a significant difference (student's t-test) in bacterial densities between challenged distant leaves of mock- and SAR-induced plants. Representative results are presented in (A) and (B) and these experiments have been repeated numerous times with similar results (see text for details). nd = not determined.