Department of Entomology, Federal University of Viçosa, Viçosa, MG, Brazil.
Department of Entomology, Federal University of Lavras, Lavras, MG, Brazil.
Insect Sci. 2019 Feb;26(1):108-118. doi: 10.1111/1744-7917.12499. Epub 2017 Aug 30.
It is well known that herbivore-induced plant defenses alter host plant quality and can affect the behavior and performance of later arriving herbivores. Effects of sequential attacks by herbivores that either suppress or induce plant defenses are less well studied. We sequentially infested leaves of tomato plants with a strain of the phytophagous spider mite Tetranychus urticae that induces plant defenses and the closely related Tetranychus evansi, which suppresses plant defenses. Plant quality was quantified through oviposition of both spider mite species and by measuring proteinase inhibitor activity using plant material that had been sequentially attacked by both herbivore species. Spider-mite oviposition data show that T. evansi could suppress an earlier induction of plant defenses by T. urticae, and T. urticae could induce defenses in plants previously attacked by T. evansi in 1 day. Longer attacks by the second species did not result in further changes in oviposition. Proteinase inhibitor activity levels showed that T. evansi suppressed the high activity levels induced by T. urticae to constitutive levels in 1 day, and further suppressed activity to levels similar to those in plants attacked by T. evansi alone. Attacks by T. urticae induced proteinase inhibitor activity in plants previously attacked by T. evansi, eventually to similar levels as induced by T. urticae alone. Hence, plant quality and plant defenses were significantly affected by sequential attacks and the order of attack does not affect subsequent performance, but does affect proteinase inhibitor activity levels. Based on our results, we discuss the evolution of suppression of plant defenses.
众所周知，食草动物诱导的植物防御会改变宿主植物的质量，并影响后来到达的食草动物的行为和表现。对食草动物的连续攻击的影响，这些食草动物要么抑制要么诱导植物防御，研究得较少。我们连续用一种诱导植物防御的植食性蜘蛛螨 Tetranychus urticae 和一种密切相关的 Tetranychus evansi 感染番茄植株的叶片，后者抑制植物防御。通过两种蜘蛛螨的产卵和使用已被两种食草动物连续攻击的植物材料测量蛋白酶抑制剂活性来量化植物质量。蜘蛛螨产卵数据表明，T. evansi 可以抑制 T. urticae 早期诱导的植物防御，而 T. urticae 可以在 1 天内诱导先前被 T. evansi 攻击的植物防御。第二种物种的更长时间攻击不会导致产卵的进一步变化。蛋白酶抑制剂活性水平表明，T. evansi 在 1 天内将 T. urticae 诱导的高水平活性抑制到组成型水平，并进一步将活性抑制到与仅受 T. evansi 攻击的植物相似的水平。T. urticae 的攻击诱导了先前受 T. evansi 攻击的植物中的蛋白酶抑制剂活性，最终达到与 T. urticae 单独诱导的相似水平。因此，植物质量和植物防御受到连续攻击的显著影响，攻击的顺序不影响后续表现，但会影响蛋白酶抑制剂活性水平。基于我们的结果，我们讨论了植物防御抑制的进化。
