Mississippi State University, Department of Biochemistry, Molecular Biology, Entomology, and Plant Pathology, 32 Creelman Street, MS 9650, Mississippi State, MS 39762, USA.
J Econ Entomol. 2012 Feb;105(1):120-8. doi: 10.1603/ec11107.
Various pests, such as those in the order Lepidoptera, frequently feed on young maize (Zea mays) plants and pose a significant threat to plant development and survival. To manage this problem, maize generates a wide variety of responses to attack by pests, from activation of wound-response pathways to the release of volatile compounds. Mp708, an inbred line resistant to feeding by the larvae of the fall armyworm (Spodoptera frugiperda J.E. Smith Lepidoptera: Noctuidae), has been developed through traditional breeding methods, but its underlying mechanisms of resistance are still not completely understood. Mp708 has been shown to have a moderately high constitutive expression of jasmonic acid (JA) before infestation by fall armyworm. However, Tx601, a genotype susceptible to feeding by fall armyworm, activates JA pathway only in response to feeding, suggesting that Mp708 is "primed" to respond swiftly to an attack. Current research indicates that fall armyworm show a lack of preference to feeding on Mp708, leading to the hypothesis that volatiles constitutively released by the plant may also play an important role in its resistance. Analysis of volatiles released by Mp708 and Tx601 in the presence and absence of fall armyworm larvae identified (E)-beta-caryophyllene, a terpenoid associated with resistance, released constitutively in Mp708. Fall armyworm fed samples of both Mp708 and Tx601 showed high transcript number of tps23, the gene responsible for the synthesis of (E)-beta-caryophyllene. In addition, fall armyworm larvae show a preference for Tx601 whorl tissue over Mp708 tissue, and the dosage of Tx601 whorl with (E)-beta-caryophyllene repels the fall armyworm.
各种害虫，如鳞翅目昆虫，经常以幼玉米（Zea mays）为食，对植物的生长和生存构成了重大威胁。为了应对这一问题，玉米对害虫的攻击产生了多种反应，从伤口反应途径的激活到挥发性化合物的释放。Mp708 是通过传统的育种方法培育出来的，它对白纹夜蛾（Spodoptera frugiperda J.E. Smith 鳞翅目：夜蛾科）幼虫的取食具有抗性，但它的抗性机制仍不完全清楚。Mp708 在受到白纹夜蛾侵害之前，茉莉酸（JA）的组成型表达水平较高。然而，Tx601 是对白纹夜蛾取食敏感的基因型，只有在取食时才激活 JA 途径，这表明 Mp708 对攻击的反应迅速。目前的研究表明，白纹夜蛾对取食 Mp708 表现出缺乏偏好，这导致了一个假设，即植物持续释放的挥发物也可能在其抗性中发挥重要作用。分析 Mp708 和 Tx601 在有无白纹夜蛾幼虫存在时释放的挥发物，鉴定出（E）-β-石竹烯，一种与抗性相关的萜类化合物，在 Mp708 中持续释放。白纹夜蛾取食 Mp708 和 Tx601 的样本显示，负责合成（E）-β-石竹烯的 tps23 基因的转录数量很高。此外，白纹夜蛾幼虫对白纹夜蛾组织表现出对白纹夜蛾组织的偏好，而含有（E）-β-石竹烯的 Tx601 轮生组织对白纹夜蛾具有驱避作用。
