HopZ1a activates JA signaling during bacterial infection.

Arabidopsis zar1-1 mutant plants were inoculated with PtoDC3000 or PtoDC3118 carrying the empty pUCP18 vector (EV), HopZ1a or HopZ1a(C216A). The transcript levels of the JA-responsive genes AtJAZ9 and AtJAZ10, as well as the SA biosynthetic gene AtICS1 were determined by quantitative RT-PCR. (A) HopZ1a induces the expression of JA-responsive genes in Arabidopsis. The abundances of AtJAZ9 and AtJAZ10 transcripts were examined at 6 hpi using AtActin as the internal standard. Relative expression levels were determined by comparing the normalized AtJAZ9 or AtJAZ10 transcripts between infected and mock-treated (leaves infiltrated with 10 mM MgSO4) samples. (B) HopZ1a reduces the expression of AtICS1 in Arabidopsis. AtICS1 transcript level was analyzed at 9 hpi using AtUBQ5 as the internal standard. Values are means ± standard deviations (as error bars) (n = 5). All experiments were repeated at least five times with similar results. The expression of HopZ1a in P. syringae was confirmed by western blots (Fig. S8).