College of Life Sciences, Nankai University, Tianjin 300071, China.
Toxins (Basel). 2018 Dec 26;11(1):7. doi: 10.3390/toxins11010007.
Alkaloids are usually thought to be responsible for protecting endophyte-infected (EI) grasses from their herbivores. For EI grasses that produce few alkaloids, can endophyte infection enhance their resistance to herbivores? Related studies are limited. In the Inner Mongolian steppe, is highly infected by endophytes, but produces few alkaloids. Locusts are the common insect herbivores of grasses. In this study, was used as plant material. Methyl jasmonate (MJ, when applied exogenously, can induce responses similar to herbivore damage) treatment was performed. The effects of endophyte infection and MJ treatment on the resistance of to were studied. We found that locusts preferred EF (endophyte-free) plants to EI plants in both choice and no-choice feeding experiments. Endophyte infection enhanced the resistance of to locusts. Endophyte infection decreased soluble sugar concentrations, while it increased the total phenolic content and phenylalanine ammonia lyase (PAL) activity, which may contribute to the resistance of to locusts. There was an interaction effect between MJ treatment and endophyte infection on the growth of the host. MJ treatment was a negative regulator of the plant growth-promoting effects of endophyte infection. There was no interaction effect between MJ treatment and endophyte infection on the defense characteristics of the host. In groups not exposed to locusts, MJ treatment and endophyte infection had a similar effect in decreasing the soluble sugar content, while increasing the total phenolic content and the PAL activity. In groups exposed to locusts, the effect of MJ treatment on the above characteristics disappeared, while the effect of endophyte infection became more obvious. All of these results suggest that even for endophytes producing few alkaloids, they could still increase the resistance of native grasses to insect herbivores. Furthermore, endophyte infection might mediate the defense responses of the host, independent of jasmonic acid (JA) pathways.
生物碱通常被认为是保护内生真菌感染（EI）草免受其食草动物侵害的原因。对于产生少量生物碱的 EI 草，内生真菌感染是否能增强其对食草动物的抵抗力？相关研究有限。在内蒙古草原， 被 内生真菌高度感染，但产生的生物碱很少。蝗虫是草的常见昆虫食草动物。在这项研究中， 使用 作为植物材料。茉莉酸甲酯（MJ，当外施时，可以诱导类似于食草动物伤害的反应）处理。研究了内生真菌感染和 MJ 处理对 抵抗蝗虫的影响。我们发现，在选择和非选择喂养实验中，蝗虫更喜欢 EF（无内生真菌）植物而不是 EI 植物。内生真菌感染增强了 对蝗虫的抵抗力。内生真菌感染降低了可溶性糖浓度，而增加了总酚含量和苯丙氨酸解氨酶（PAL）活性，这可能有助于 抵抗蝗虫。MJ 处理和内生真菌感染对宿主生长有相互作用效应。MJ 处理是内生真菌感染促进植物生长效应的负调节剂。MJ 处理和内生真菌感染对宿主防御特性没有相互作用效应。在未暴露于蝗虫的组中，MJ 处理和内生真菌感染对降低可溶性糖含量有相似的作用，而增加总酚含量和 PAL 活性。在暴露于蝗虫的组中，MJ 处理对上述特征的影响消失，而内生真菌感染的影响变得更加明显。所有这些结果表明，即使对于产生少量生物碱的内生真菌，它们仍然可以提高本地草对昆虫食草动物的抵抗力。此外，内生真菌感染可能介导宿主的防御反应，而不依赖于茉莉酸（JA）途径。
