Ultraviolet-B enhances the resistance of multiple plant species to lepidopteran insect herbivory through the jasmonic acid pathway.

Land plants protect themselves from ultraviolet-B (UV-B) by accumulating UV-absorbing metabolites, which may also function as anti-insect toxins. Previous studies have shown that UV-B enhances the resistance of different plant species to pierce-sucking pests; however, whether and how UV-B influences plant defense against chewing caterpillars are not well understood. Here we show that UV-B treatment increased Spodoptera litura herbivory-induced jasmonic acid (JA) production in Arabidopsis and thereby Arabidopsis exhibited elevated resistance to S. litura. Using mutants impaired in the biosynthesis of JA and the defensive metabolites glucosinolates (GSs), we show that the UV-B-induced resistance to S. litura is dependent on the JA-regulated GSs and an unidentified anti-insect metabolite(s). Similarly, UV-B treatment also enhanced the levels of JA-isoleucine conjugate and defense-related secondary metabolites in tobacco, rice, and maize after these plants were treated with simulated herbivory of lepidopteran insects; consistently, these plants showed elevated resistance to insect larvae. Using transgenic plants impaired in JA biosynthesis or signaling, we further demonstrate that the UV-B-enhanced defense responses also require the JA pathway in tobacco and rice. Our findings reveal a likely conserved JA-dependent mechanism by which UV-B enhances plant defense against lepidopteran insects.

陆生植物通过积累吸收紫外线的代谢物来保护自身免受紫外线 - B（UV - B）的伤害，这些代谢物可能还具有抗虫毒素的功能。先前的研究表明，UV - B增强了不同植物物种对刺吸式害虫的抗性；然而，UV - B是否以及如何影响植物对咀嚼式毛虫的防御还不太清楚。在此我们表明，UV - B处理增加了拟南芥中斜纹夜蛾取食诱导的茉莉酸（JA）的产生，从而使拟南芥对斜纹夜蛾表现出更高的抗性。通过使用茉莉酸生物合成以及防御性代谢物硫代葡萄糖苷（GSs）受损的突变体，我们表明UV - B诱导的对斜纹夜蛾的抗性依赖于茉莉酸调节的硫代葡萄糖苷以及一种（或多种）未知的抗虫代谢物。同样，在烟草、水稻和玉米经模拟鳞翅目昆虫取食处理后，UV - B处理也提高了茉莉酸 - 异亮氨酸共轭物和与防御相关的次生代谢物的水平；一致地，这些植物对昆虫幼虫表现出更高的抗性。通过使用茉莉酸生物合成或信号传导受损的转基因植物，我们进一步证明在烟草和水稻中，UV - B增强的防御反应也需要茉莉酸途径。我们的研究结果揭示了一种可能保守的依赖茉莉酸的机制，通过该机制UV - B增强了植物对鳞翅目昆虫的防御。