Department of Molecular Ecology, Max-Planck-Institute for Chemical Ecology, Beutenberg Campus, D-07745 Jena, Germany.
Plant Physiol. 2011 Apr;155(4):1936-46. doi: 10.1104/pp.110.170936. Epub 2011 Feb 7.
Folivory is the best studied plant-herbivore interaction, but it is unclear whether the signaling and resistance traits important for the defense of leaves are also important for other plant parts. Larvae of the tobacco stem weevil, Trichobaris mucorea, burrow into stems of Nicotiana attenuata and feed on the pith. Transgenic N. attenuata lines silenced in signaling and foliar defense traits were evaluated in a 2-year field study for resistance against attack by naturally occurring T. mucorea larva. Plants silenced in early jasmonic acid (JA) biosynthesis (antisense [as]-lipoxygenase3 [lox3]; inverted repeat [ir]-allene oxide cyclase), JA perception (as-coronatine insensitive1), proteinase inhibitors (ir-pi), and nicotine (ir-putrescine methyl-transferase) direct defenses and lignin (ir-cad) biosynthesis were infested more frequently than wild-type plants. Plants unable to emit C(6) aldehydes (as-hpl) had lower infestation rates, while plants silenced in late steps in JA biosynthesis (ir-acyl-coenzyme A oxidase, ir-opr) and silenced in diterpene glycoside production (ir-geranylgeranyl pyrophosphate synthase) did not differ from wild type. Pith choice assays revealed that ir-putrescine methyl-transferase, ir-coronatine insensitive1, and ir-lox3 pith, which all had diminished nicotine levels, were preferred by larvae compared to wild-type pith. The lack of preference for ir-lox2 and ir-cad piths, suggest that oviposition attraction and vascular defense, rather than pith palatability accounts for the higher attack rates observed for these plants. We conclude that traits that influence a plant's apparency, stem hardness, and pith direct defenses all contribute to resistance against this herbivore whose attack can be devastating to N. attenuata's fitness.
食叶性是研究得最多的植物-草食动物相互作用，但目前尚不清楚对叶片防御很重要的信号和抗性特征是否对其他植物部位也同样重要。烟草茎象甲的幼虫钻入黄花烟草的茎中，以髓为食。在一项为期两年的田间研究中，评估了信号和叶防御特性沉默的转基因黄花烟草植株对天然烟草茎象甲幼虫攻击的抗性。早期茉莉酸（JA）生物合成（反义[as]-脂氧合酶 3 [lox3]；反向重复 [ir]-丙二烯氧化物环化酶）、JA 感知（as-冠瘿碱不敏感 1）、蛋白酶抑制剂（ir-pi）和尼古丁（ir-腐胺甲基转移酶）直接防御和木质素（ir-cad）生物合成沉默的植物比野生型植物更容易受到侵扰。不能发出 C(6)醛（as-hpl）的植物侵染率较低，而 JA 生物合成后期步骤沉默的植物（ir-acyl-coenzyme A 氧化酶，ir-opr）和二萜糖苷生产沉默的植物（ir-geranylgeranyl pyrophosphate synthase）与野生型植物没有差异。髓选择试验表明，与野生型髓相比，ir-腐胺甲基转移酶、ir-冠瘿碱不敏感 1 和 ir-lox3 髓（这些髓的尼古丁水平都降低了），都更受幼虫的青睐。缺乏对 ir-lox2 和 ir-cad 髓的偏好表明，产卵吸引力和血管防御，而不是髓的适口性，是导致这些植物观察到的更高攻击率的原因。我们的结论是，影响植物外观、茎硬度和髓直接防御的特征都有助于抵抗这种食草动物的侵害，而这种食草动物的攻击可能对黄花烟草的适应性造成毁灭性的影响。
