Liu Jie, Legarrea Saioa, Kant Merijn R
Section Molecular and Chemical Ecology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, Netherlands.
Front Plant Sci. 2017 Dec 13;8:2128. doi: 10.3389/fpls.2017.02128. eCollection 2017.
Herbivory induces plant defenses. These responses are often costly, yet enable plants under attack to reach a higher fitness than they would have reached without these defenses. Spider mites ( ssp.) are polyphagous plant-pests. While most strains of the species induce defenses at the expense of their performance, the species suppresses plant defenses and thereby maintains a high performance. Most data indicate that suppression is a mite-adaptive trait. Suppression is characterized by a massive down-regulation of plant gene-expression compared to plants infested with defense-inducing mites as well as compared to control plants, albeit to a lesser extent. Therefore, we hypothesized that suppression may also benefit a plant since the resources saved during down-regulation could be used to increase reproduction. To test this hypothesis, we compared fruit and viable seed production of uninfested tomato plants with that of plants infested with defense-inducing or defense-suppressing mites. Mite-infested plants produced fruits faster than control plants albeit in lower total amounts. The -infested plants produced the lowest number of fruits. However, the number of viable seeds was equal across treatments at the end of the experiment. Nonetheless, at this stage control plants were still alive and productive and therefore reach a higher lifetime fitness than mite-infested plants. Our results indicate that plants have plastic control over reproduction and can speed up fruit- and seed production when conditions are unfavorable. Moreover, we showed that although suppressed plants are less productive in terms of fruit production than induced plants, their lifetime fitness was equal under laboratory conditions. However, under natural conditions the fitness of plants such as tomato will also depend on the efficiency of seed dispersal by animals. Hence, we argue that the fitness of induced plants in the field may be promoted more by their higher fruit production relative to that of their suppressed counterparts.
食草作用会诱导植物产生防御反应。这些反应往往代价高昂，但能使遭受攻击的植物获得比没有这些防御时更高的适合度。叶螨（叶螨属）是多食性植物害虫。虽然该物种的大多数品系会以自身生长性能为代价诱导植物防御，但该物种会抑制植物防御，从而保持较高的生长性能。大多数数据表明，抑制是叶螨的一种适应性特征。与受诱导防御的叶螨侵染的植物以及对照植物相比，抑制的特征是植物基因表达大量下调，尽管程度较小。因此，我们推测抑制可能对植物也有益，因为下调过程中节省的资源可用于增加繁殖。为了验证这一假设，我们比较了未受侵染的番茄植株与受诱导防御或抑制防御的叶螨侵染的植株的果实和可存活种子产量。受叶螨侵染的植株比对照植株更快结出果实，尽管总量较少。受[叶螨品系名称]侵染的植株结出的果实数量最少。然而，在实验结束时，各处理间可存活种子的数量是相等的。尽管如此，在这个阶段对照植株仍然存活且有产量，因此其一生的适合度比受叶螨侵染的植株更高。我们的结果表明，植物对繁殖有灵活的控制能力，在条件不利时可以加快果实和种子的生产。此外，我们表明，虽然受抑制的植株在果实产量方面比受诱导的植株低，但在实验室条件下它们一生的适合度是相等的。然而，在自然条件下，像番茄这样的植物的适合度还将取决于动物传播种子的效率。因此，我们认为，相对于受抑制的同类植物，受诱导的植物较高的果实产量可能会在田间更能提升其适合度。
