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Conifers have evolved sophisticated terpenoid defenses for protection against herbivores and pathogens. Pinus massoniana Lamb. is the most widely distributed pioneer afforestation and resin tree species in China, but is seriously harmed by pine wilt disease. Monochamus alternatus is the main vector of pine wilt disease in China. Monoterpenes, sesquiterpenes and diterpenes, the main secondary defensive compounds of P. massoniana, are catalyzed by different terpene synthases (TPSs), which participate in the important defense pathways against external biotic and abiotic stresses. Here, we aimed to identify the terpene synthases (TPSs) in P. massoniana, responding to the feeding of M. alternatus, and to characterize the functions and products of the mono-TPSs. We identified six differentially expressed TPS genes in the P. massoniana fed upon by M. alternatus, including four mono-TPS and two sesqui-TPS genes. The functions of the four mono-TPSs were verified by analysis of the main product and by-products of these mono-TPSs. (+)-α-Pinene, (−)-α-pinene, and limonene were the major products of TPS (+)-α-pinene, TPS (−)-α-pinene, and TPS limonene, respectively, but TPS (−)-β-pinene only catalyzed a trace amount of (−)-β-pinene in the products. Our findings shed light on the potential relationships between the structure of terpene synthases and their corresponding products. [ABSTRACT FROM AUTHOR]

Plants play an important role in interactions between insect herbivores and their pathogens. The ability of host plants to modify the infectivity of entomopathogens in herbivorous insects has been widely documented. However, the plants' nutrients have always been neglected as a factor contributing to variation in the susceptibility of insect herbivores to entomopathogens. The fall-webworm (FWW), Hyphantria cunea Drury, is a typical polyphagous caterpillar, and the Hyphantria cunea nucleopolyhedrovirus (HycuNPV) is a distinctly specialized baculovirus for the FWW, which is safe for other organisms and has been effectively used as a biological insecticide against H. cunea in China. In this study, we investigated the nutrient components of four host plant species, i.e., Prunus serrulate, Cerasus serrulate, Camptotheca acuminata, and Populus deltoides, and their effects on the susceptibility of H. cunea larvae to HycuNPV. The HycuNPV-infected larvae fed on P. deltoides leaves exhibited higher survival rates, longer survival times, more food intake, and gained larger body size. These biological parameters were positively correlated with the nitrogen components of host plant leaves. Moreover, the larval antioxidant enzymes exhibited different responses to HycuNPV. HycuNPV infection significantly triggered the catalase (CAT) and prophenoloxidase (PPO) enzyme activity levels of H. cunea larvae. The uninfected larvae fed on poplar leaves induced a robust increase in the POD activity, which could scavenge extra reactive oxygen species and provide a protective effect against the HycuNPV. In conclusion, the plant-mediated effects of HycuNPV on the FWW have been investigated in this study. The nitrogen content in dietary was an essential factor in determining the insect herbivore susceptibility to entomopathogenic viruses, and it helped explain variations in the susceptibility of pests to the entomopathogenic viruses and aid in developing more robust tolerance monitoring assays in the lab that reflect the performance of pests in the field. [ABSTRACT FROM AUTHOR]

Native to Asia, Euwallacea interjectus (Blandford) (Coleoptera: Curculionidae: Scolytinae) is a destructive and invasive pest of live trees, and now it has been found in the United States and Argentina. In recent years, this pest appeared in high densities in poplar monocultures from Eastern China (Jiangsu and Shanghai) and Argentina and caused significant poplar mortality. However, the origin of the pests related to tree damage and the Fusarium mutualists from some poplar zones in China remained unclear. Here, we provided a broader phylogeographic analysis of E. interjectus based on the mitochondrial gene (cytochrome c oxidase I) to determine the global genetic structure of this species. Five mitochondrial lineages were found in the native area. Populations introduced to the United States were originated from 4 localities. The Argentine population was derived from Japan. The species was observed with strikingly high level of cytochrome c oxidase I intraspecific divergence that exceeded interspecific divergence, but the high intraspecific variation was correlated with geographical locations among the native populations. Two nuclear genes (arginine kinase and carbamoyl-phosphate synthetase 2-aspartate transcarbamylase-dihydroorotase) were more conservative, and intraspecific differences were lower than interspecific differences. The mitochondrial genetic variation was probably caused by evolution of lineages among geographically isolated populations. But it is immature to infer the existence of cryptic species based on cytochrome c oxidase I differences. All samples collected from poplar populations were indigenous and formed close relationship with a specimen from eastern and southern China. Surprisingly, pests from poplar populations in Jiangsu and Shanghai showed different haplotypes and mutualists. This suggested that the control strategies should consider the genetic and mutualistic diversity of beetles at different poplar localities., (© The Author(s) 2024. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)