Department of Entomology, University of Arkansas, Fayetteville, Arkansas 72701, USA.
Plant Physiol. 2012 Apr;158(4):2028-41. doi: 10.1104/pp.111.191262. Epub 2012 Jan 30.
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.
我们在此报告，ω-3 脂肪酸去饱和酶 7（FAD7）功能的破坏增强了植物对蚜虫的防御。番茄（Solanum lycopersicum）中的 prosystemin 介导反应的抑制物 2（spr2）突变消除了 FAD7 的功能，降低了马铃薯蚜虫（Macrosiphum euphorbiae）的定殖行为、存活率和繁殖力。同样，野生型番茄植物中 LeFAD7 表达的反义抑制也减少了蚜虫的侵害。spr2 突变体的抗蚜性与水杨酸（SA）水平的提高和编码病程相关蛋白 P4 的 mRNA 有关。引入萘羟化酶基因，该基因抑制 SA 积累，可恢复 spr2 对野生型蚜虫的敏感性。当我们利用病毒诱导的基因沉默来抑制 SA 依赖性防御的许多正调节剂 NPR1 的表达时，spr2 的抗性也会丧失。FAD7 抑制了通过 SA 和 NPR1 介导的对蚜虫的防御作用，尽管 FAD7 的功能丧失也抑制了茉莉酸（JA）的合成，但这种去饱和酶对蚜虫抗性的影响不依赖于 JA；其他 JA 合成受损的突变体（acx1）或感知（jai1-1）表现出与野生型相同的蚜虫敏感性，而 spr2 在施用茉莉酸甲酯时仍保持抗蚜性。因此，FAD7 可能通过对 JA 合成和 SA 信号转导的独立影响，影响 JA 依赖的抗咀嚼昆虫防御和 SA 依赖的抗蚜虫防御。拟南芥（Arabidopsis thaliana）突变体 Atfad7-2 和 Atfad7-1fad8 与野生型对照相比，对绿桃蚜（Myzus persicae）也表现出增强的抗性，表明 FAD7 至少在两个植物科中影响植物-蚜虫相互作用。
