Gaffke Alexander M, Shapiro-Ilan David, Alborn Hans T
Center for Medical, Agricultural and Veterinary Entomology, Agricultural Research Service, United States Department of Agriculture, Gainesville, FL, United States.
Department of Entomology, Louisiana State University, Baton Rouge, LA, United States.
Front Physiol. 2022 Sep 14;13:978359. doi: 10.3389/fphys.2022.978359. eCollection 2022.
Plants attacked by insects commonly mobilize various defense mechanisms, including the biosynthesis and release of so-called herbivore-induced plant volatiles (HIPVs). Entomopathogenic nematodes (EPNs) can be attracted to these belowground HIPVs, which can enhance biocontrol services from EPNs. However, recent research has also demonstrated that HIPVs can induce and initiate insect immune responses, decreasing the insect's susceptibility to pathogens and parasites. Therefore, experiments were conducted to test the impact of HIPVs on insects and EPNs during the initial stage of EPN infection. Compounds that can impact EPN attraction and infectivity such as pregeijerene, β-caryophyllene, and α-pinene, and compounds that have been determined to increase or decrease susceptibility of insects to pathogens, such as ()-3-hexenyl acetate, linalool, and β-ocimene, were selected. Exposure of larvae to pregeijerene, linalool, β-ocimene and α-pinene during invasion significantly increased mortality of and after 48 h. Larval treatment with β-caryophyllene only increased mortality for . (Z)-3-hexenyl acetate did not cause differential mortality from the controls for either nematode species. In additional experiments, we found that EPNs exposed to α-pinene and linalool were more readily recognized by the insects' immune cells compared to the control treatment, thus the observed increased mortality was likely due to HIPVs-EPN interactions with the insect's immune system. These results show that the presence of HIPVs can impact EPN survival in the model host, .
受到昆虫攻击的植物通常会调动各种防御机制，包括所谓的食草动物诱导植物挥发物（HIPVs）的生物合成和释放。昆虫病原线虫（EPNs）会被这些地下HIPVs吸引，这可以增强EPNs的生物防治作用。然而，最近的研究也表明，HIPVs可以诱导并引发昆虫的免疫反应，降低昆虫对病原体和寄生虫的易感性。因此，开展了实验来测试在EPN感染初期HIPVs对昆虫和EPNs的影响。选择了能够影响EPN吸引力和感染力的化合物，如前格伊烯、β-石竹烯和α-蒎烯，以及已确定会增加或降低昆虫对病原体易感性的化合物，如（Z）-3-己烯基乙酸酯、芳樟醇和β-罗勒烯。在侵染期间让幼虫接触前格伊烯、芳樟醇、β-罗勒烯和α-蒎烯，48小时后显著增加了两种线虫的死亡率。用β-石竹烯处理幼虫仅增加了一种线虫的死亡率。（Z）-3-己烯基乙酸酯对两种线虫的死亡率与对照相比均无差异。在额外的实验中，我们发现与对照处理相比，接触α-蒎烯和芳樟醇的EPNs更容易被昆虫的免疫细胞识别，因此观察到的死亡率增加可能是由于HIPVs-EPN与昆虫免疫系统的相互作用。这些结果表明，HIPVs的存在会影响模式宿主中EPNs的存活。
