Figure 4.

irx-Mediated Resistance Is SA-, ET-, and JA-Independent.

(A) Analysis of the susceptibility to R. solanacearum and P. cucumerina of irx1-6 double mutants with defects in the SA (irx1-6 NahG), ET (irx1-6 ein2-5), or JA (irx1-6 coi1-1) signal transduction pathway. Average disease ratings (±sd) of the indicated genotypes at 10 d after inoculation are represented. The disease rating varies between 0 (no symptoms) and 4 (dead plants). At least 10 plants per genotype were tested. Asterisks indicate values significantly different (P < 0.01, t test) from those of wild-type plants.

(B) Disease symptoms of P. cucumerina–inoculated plants at 12 d after inoculation.

(C) Expression analysis of SA and ET/JA marker genes in irx1-6 double mutants. RNA gel blot of PR1 and PDF1.2 defense genes in wild-type plants, single mutants, NahG transgenic plants, and double mutants. Total RNA (2.5 μg/lane) was extracted from plants collected at the indicated days after inoculation (dpi) with P. cucumerina (Pc) or treated with water (mock [M]). Blots were hybridized with the PR1, PDF1.2, and Pc ITS probes. β-Tubulin (β-TUB) hybridization was included as a loading control. Three independent experiments were performed and gave similar results.