title: Densovirus is a mutualistic symbiont of a global crop pest (Helicoverpa armigera) and protects against a baculovirus and Bt biopesticide.
abstract: Mutualistic associations between symbiotic bacteria and their hosts are common within insect systems. However, viruses are often considered as pathogens even though some have been reported to be beneficial to their hosts. Herein, we report a novel densovirus, Helicoverpa armigera densovirus-1 (HaDNV-1) that appears to be beneficial to its host. HaDNV-1 was found to be widespread in wild populations of H. armigera adults (>67% prevalence between 2008 and 2012). In wild larval populations, there was a clear negative interaction between HaDNV-1 and H. armigera nucleopolyhedrovirus (HaNPV), a baculovirus that is widely used as a biopesticide. Laboratory bioassays revealed that larvae hosting HaDNV-1 had significantly enhanced resistance to HaNPV (and lower viral loads), and that resistance to Bacillus thuringiensis (Bt) toxin was also higher at low doses. Laboratory assays indicated that the virus was mainly distributed in the fat body, and could be both horizontally- and vertically-transmitted, though the former occurred only at large challenge doses. Densovirus-positive individuals developed more quickly and had higher fecundity than uninfected insects. We found no evidence for a negative effect of HaDNV-1 infection on H. armigera fitness-related traits, strongly suggesting a mutualistic interaction between the cotton bollworm and its densovirus.
authors.affiliation: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, People's Republic of China; Tobacco Research Institute, Chinese Academy of Agricultural Sciences, Qingdao, People's Republic of China.
authors.forename: Pengjun
authors.initials: P
authors.lastname: Xu
authors.affiliation: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, People's Republic of China.
authors.forename: Yongqiang
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Lancaster Environment Centre, Lancaster University, Lancaster, United Kingdom.
authors.forename: Robert I
authors.initials: RI
authors.lastname: Graham
authors.affiliation: Lancaster Environment Centre, Lancaster University, Lancaster, United Kingdom.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Wilson
authors.affiliation: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, People's Republic of China.
authors.forename: Kongming
authors.initials: K
authors.lastname: Wu
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001427:Bacterial Toxins / Q000009:adverse effects; D016367:Baculoviridae / Q000502:physiology*; D017990:Densovirus / Q000502:physiology*; D005260:Female; D007814:Larva; D008297:Male; D009036:Moths / Q000187:drug effects / Q000821:virology*; D017924:Nucleopolyhedroviruses / Q000502:physiology*; D010572:Pest Control, Biological; D013559:Symbiosis; D019562:Viral Load
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins