Abstract
We report here that disruption of function of the ω-3 FATTY ACID DESATURASE7 (FAD7) enhances plant defenses against aphids. The suppressor of prosystemin-mediated responses2 (spr2) mutation in tomato (Solanum lycopersicum), which eliminates the function of FAD7, reduces the settling behavior, survival, and fecundity of the potato aphid (Macrosiphum euphorbiae). Likewise, the antisense suppression of LeFAD7 expression in wild-type tomato plants reduces aphid infestations. Aphid resistance in the spr2 mutant is associated with enhanced levels of salicylic acid (SA) and mRNA encoding the pathogenesis-related protein P4. Introduction of the Naphthalene/salicylate hydroxylase transgene, which suppresses SA accumulation, restores wild-type levels of aphid susceptibility to spr2. Resistance in spr2 is also lost when we utilize virus-induced gene silencing to suppress the expression of NONEXPRESSOR OF PATHOGENESIS-RELATED PROTEINS1 (NPR1), a positive regulator of many SA-dependent defenses. These results indicate that FAD7 suppresses defenses against aphids that are mediated through SA and NPR1. Although loss of function of FAD7 also inhibits the synthesis of jasmonate (JA), the effects of this desaturase on aphid resistance are not dependent on JA; other mutants impaired in JA synthesis (acx1) or perception (jai1-1) show wild-type levels of aphid susceptibility, and spr2 retains aphid resistance when treated with methyl jasmonate. Thus, FAD7 may influence JA-dependent defenses against chewing insects and SA-dependent defenses against aphids through independent effects on JA synthesis and SA signaling. The Arabidopsis (Arabidopsis thaliana) mutants Atfad7-2 and Atfad7-1fad8 also show enhanced resistance to the green peach aphid (Myzus persicae) compared with wild-type controls, indicating that FAD7 influences plant-aphid interactions in at least two plant families.
Highlights
IntroductionWe report here that disruption of function of the ω-3-fatty acid desaturase FAD7 enhances plant defenses against aphids
To determine whether the effect of spr2 on aphid performance is due to inhibition of JA synthesis, we examined aphid performance on acx1, which carries a mutation that results in a loss of function of acyl-coA oxidase 1A, thereby blocking the β-oxidation step of JA synthesis (Li et al, 2005)
Plants must defend themselves against a broad array of pests, including insect herbivores that utilize a diversity of feeding strategies to exploit their hosts
Summary
We report here that disruption of function of the ω-3-fatty acid desaturase FAD7 enhances plant defenses against aphids. Aphid resistance in the spr mutant is associated with enhanced levels of salicylic acid (SA) and mRNA encoding the pathogenesisrelated protein P4. PATHOGENESIS-RELATED PROTEINS1 (NPR1), a positive regulator of many SA-dependent defenses These results indicate that FAD7 suppresses defenses against aphids that are mediated through SA and NPR1. Loss of function of FAD7 inhibits synthesis of jasmonate (JA), the effects of this desaturase on aphid resistance are not dependent on JA; other mutants impaired in JA synthesis (acx1) or perception (jai1-1) show WT levels of aphid susceptibility, and spr retains aphid resistance when treated with methyl jasmonate. Arabidopsis (Arabidopsis thaliana) mutants fad and fad7-1fad show enhanced resistance to the green peach aphid (Myzus persicae) compared to WT controls, indicating that
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