Figure 6.

ACIF1 Is Required for N Gene–Mediated Resistance Responses to TMV Infection.

(A) Photographs of tobacco leaves at 4 d after rub-inoculation with TMV. Cf-9 control plants, as well as three lines expressing ACIF1(P64A) and two lines with RNAi silencing of ACIF1, are shown.

(B) Mean (±se) number of TMV lesions formed at 4 DPI on RNAi-ACIF1, ACIF1(P64A), and the parental control (Cf-9) tobacco. At least two independent transgenic lines were examined per construct (eight plants per line), and the experiment was repeated more than four times with similar results. Means were compared by Student's t test. Different letters above the bars indicate significantly different means (P < 0.05).

(C) Mean (±se) TMV lesion diameter at 7 DPI on RNAi-ACIF1, ACIF1(P64A), and the parental control (Cf-9) tobacco. Means were compared by Student's t test. Different letters above the bars indicate significantly different means (P < 0.05). Per line, we quantified at least 80 lesions.

(D) Mean (±se; six biologically independent samples per line) SA (white bars) and SAG (gray bars) levels in the primary infected leaf of the indicated lines at 7 d after TMV infection. Tobacco cv Petite Havana was included as a susceptible control (lacking the N gene) and Cf-9 tobacco as a resistant control (carrying the N gene).

(E) Mean (±se) TMV lesion diameter in F1 crosses between NahG tobacco (nn; lacking the N gene) and RNAi-ACIF1, ACIF1(P64A), and the parental control (Cf-9) tobacco plants (homozyogous for the N gene; NN) at 7 d after TMV inoculation. Comparison of the means with Student's t test indicated that none of the means was significantly different (40 lesions measured per plant line).