title: Insecticidal Activity of Melaleuca alternifolia Essential Oil and RNA-Seq Analysis of Sitophilus zeamais Transcriptome in Response to Oil Fumigation.
abstract: BACKGROUND
  The cereal weevil, Sitophilus zeamais is one of the most destructive pests of stored cereals worldwide. Frequent use of fumigants for managing stored-product insects has led to the development of resistance in insects. Essential oils from aromatic plants including the tea oil plant, Melaleuca alternifolia may provide environmentally friendly alternatives to currently used pest control agents. However, little is known about molecular events involved in stored-product insects in response to plant essential oil fumigation.
  
  
  RESULTS
  M. alternifolia essential oil was shown to possess the fumigant toxicity against S. zeamais. The constituent, terpinen-4-ol was the most effective compound for fumigant toxicity. M. alternifolia essential oil significantly inhibited the activity of three enzymes in S. zeamais, including two detoxifying enzymes, glutathione S-transferase (GST), and carboxylesterase (CarE), as well as a nerve conduction enzyme, acetylcholinesterase (AChE). Comparative transcriptome analysis of S. zeamais through RNA-Seq identified a total of 3,562 differentially expressed genes (DEGs), of which 2,836 and 726 were up-regulated and down-regulated in response to M. alternifolia essential oil fumigation, respectively. Based on gene ontology (GO) analysis, the majority of DEGs were involved in insecticide detoxification and mitochondrial function. Furthermore, an abundance of DEGs mapped into the metabolism pathway in the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database were associated with respiration and metabolism of xenobiotics, including cytochrome P450s, CarEs, GSTs, and ATP-binding cassette transporters (ABC transporters). Some DEGs mapped into the proteasome and phagosome pathway were found to be significantly enriched. These results led us to propose a model of insecticide action that M. alternifolia essential oil likely directly affects the hydrogen carrier to block the electron flow and interfere energy synthesis in mitochondrial respiratory chain.
  
  
  CONCLUSIONS
  This is the first study to perform a comparative transcriptome analysis of S. zeamais in response to M. alternifolia essential oil fumigation. Our results provide new insights into the insecticidal mechanism of M. alternifolia essential oil fumigation against S. zeamais and eventually contribute to the management of this important agricultural pest.
authors.affiliation: School of Plant Protection, Anhui Agricultural University, Hefei, China.
authors.forename: Min
authors.initials: M
authors.lastname: Liao
authors.affiliation: School of Plant Protection, Anhui Agricultural University, Hefei, China.
authors.forename: Jin-Jing
authors.initials: JJ
authors.lastname: Xiao
authors.affiliation: School of Plant Protection, Anhui Agricultural University, Hefei, China.
authors.forename: Li-Jun
authors.initials: LJ
authors.lastname: Zhou
authors.affiliation: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Provincial Key Laboratory for Agri-Food Safety, Hefei, China.
authors.forename: Xiang-Wei
authors.initials: XW
authors.lastname: Wu
authors.affiliation: Provincial Key Laboratory for Agri-Food Safety, Hefei, China.
authors.forename: Ri-Mao
authors.initials: RM
authors.lastname: Hua
authors.affiliation: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China.
authors.forename: Gui-Rong
authors.initials: GR
authors.lastname: Wang
authors.affiliation: School of Plant Protection, Anhui Agricultural University, Hefei, China.|Provincial Key Laboratory for Agri-Food Safety, Hefei, China.
authors.forename: Hai-Qun
authors.initials: HQ
authors.lastname: Cao
mesh_terms: D000818:Animals; D005651:Fumigation / Q000379:methods*; D005786:Gene Expression Regulation / Q000187:drug effects; D031650:Melaleuca / Q000737:chemistry*; D009822:Oils, Volatile / Q000737:chemistry / Q000633:toxicity*; D010938:Plant Oils / Q000737:chemistry / Q000633:toxicity*; D059467:Transcriptome / Q000187:drug effects*; D048889:Weevils / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics
chemical_list: D009822:Oils, Volatile; D010938:Plant Oils