Fig. 1

Identification of positive regulator candidates affecting hrpX expression by sacB strategy. Xcc wild type train 8004 and the deletion mutant strain ΔhrpG were used as controls. The principle in this strategy is that strain 8004/pL6hrpXsacB cannot grow on the minimal medium containing 5% sucrose, because the expression of the hrpX-promoter-driven sacB gene is lethal to the cells under these conditions, and only the strains with a mutation (i.e., deletion mutant of hrpG, ΔhrpG) impeding the expression of hrpX (i.e. strain ΔhrpG/pL6hrpXsacB, or disrupting the sacB gene, or the wild-type strain 8004 and the deletion mutant strain ΔhrpG can grow. a, wild-type strain 8004; b, 8004/pL6hrpXsacB; c, ΔhrpG/pL6hrpXsacB; d, the deletion mutant strain ΔhrpG