Isolation and characterization of NfV-1
Text by Steven Valles
A short sequence with virus similarity was previously identified within a transcriptome shotgun assembly from the tawny crazy ant, Nylanderia fulva. RACE reactions using this sequence as template resulted in the acquisition of the complete genome sequence of a new virus, Nylanderia fulva virus 1 (NfV-1). NfV-1 is a positive-sense, single-stranded RNA virus with unusual genome characteristics. The virus was found in all developmental stages, including brood, workers, and queens of tawny crazy ant colonies. Some queens infected with NfV-1 exhibited decreased fecundity. Baits were used to transmit the virus to uninfected tawny crazy ant colonies suggesting that the virus may have use as a biopesticide to control the ant.
Tawny crazy ant, Nylanderia fulva, is an invasive ant species that was introduced recently into the United States and Caribbean. While the tawny crazy ant is very small (about 2.5 mm long), populations reach enormous levels—so large, in fact, that dead carcasses are cleaned-up by the bucketful! (See Fig. 1) Furthermore, anecdotes of occurrences of tawny crazy ants forcing people to move away from infested properties are also known. A complete lack of known natural enemies, at the time we began the study, served as our inspiration to discover viruses that could be used to control tawny crazy ant naturally and sustainably. One virus was discovered and named Nylanderia fulva virus 1 (NfV-1). NfV-1 is a positive-sense, single-stranded RNA virus with unusual genome characteristics, including a single predicted jelly-roll fold capsid protein encoded downstream of the replicase within a single long open reading frame. Phylogenetic analyses revealed a new clade of viruses (proposed family Solinviviridae) comprising NfV-1, Solenopsis invicta virus 3, and several sequences derived from insect transcriptome shotgun assemblies. NfV-1 infects all developmental stages of the tawny crazy ant, except eggs, and is easily transmitted inter-colonially with baits. Thus, it has characteristics consistent with use as a biopesticide. Additional studies are underway to develop the virus as a classical biological control agent and/or biopesticide.
Photograph of a tawny crazy ant-infested area treated with insecticide. The dark patches (arrow) are extremely large densities of dead carcasses of the ant. Inset is a close-up photograph of an adult worker of Nylanderia fulva (Photos by D. Oi and S.D. Porter).
Introducing the authors
Steven M. Valles (pictured) is a Research Entomologist with the USDA, Agricultural Research Service, USA. James J. Becnel is a Research Entomologist with the USDA, Agricultural Research Service, USA. David H. Oi is a Research Entomologist with the USDA, Agricultural Research Service, USA. John S. LaPolla is an Associate Professor at Towson University, USA. James K. Wetterer is Professor at Florida Atlantic University, USA. Andrew E. Firth is a Research Fellow at the University of Cambridge, UK.
About the research
Isolation and characterization of Nylanderia fulva virus 1, a positive-sense, single-stranded RNA virus infecting the tawny crazy ant, Nylanderia fulva
Steven M. Valles, David H. Oi, James J. Becnel, James K. Wetterer, John S. LaPolla, Andrew E. Firth
Virology, Volume 496, September 2016, Pages 244–254