Figure 6.

Loss of function of FAD7 enhances the expression of the SA-responsive gene P4 and local SA accumulation in response to aphid feeding but suppresses the expression of the JA-responsive gene PI-II. A and B, Wild-type (WT; cv Castlemart) and spr2 tomato plants were challenged with the potato aphid (100 aphids confined to a single leaf with a sleeve cage) or mock inoculated with empty cages, and P4 and PI-II transcript abundance was analyzed 48 h after inoculation. Expression values were calculated by RT-qPCR relative to the wild-type mock-inoculated control, normalized using the RPL2 gene, and analyzed by two-way ANOVA. Error bars represent ± se (n = 4). ** P < 0.001. C and D, Wild-type (cv Castlemart) and spr2 tomato plants were challenged with potato aphids or mock inoculated with empty cages (60 aphids confined to the three terminal leaflets with a sleeve cage; five plants per genotype per time point). At 24 and 48 h after inoculation, total, free, and bound SA were quantified by HPLC in infested or mock-inoculated leaflets. Values were analyzed by ANOVA, and mean separations were performed using Student’s t test. Bars of the same pattern ± se with different lowercase letters are significantly different at α = 0.05; bars with different uppercase letters show significant differences in total SA content (free + bound). FW, Fresh weight.