Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/24/2018
Publication Date: 2/21/2018
Citation: Valles, S.M., Porter, S.D., Calcaterra, L.A. 2018. Prospecting for viral natural enemies of the fire ant Solenopsis invicta in Argentina. PLoS ONE. 13(2): e0192377. https://doi.org/10.1371/journal.pone.0192377.
DOI: https://doi.org/10.1371/journal.pone.0192377

Interpretive Summary: The red imported fire ant was introduced into the United States in the 1930s and currently infests about 300 million acres. It is estimated to cause $6 billion in annual economic losses to livestock and agricultural production and poses a serious threat to human health. Biological control is widely considered the most sustainable method of controlling the fire ant over its entire range. Viruses can plan an important role in providing sustainable and natural control of fire ants in the U.S. Scientists at the USDA-ARS, Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Florida, and Fundacion para el Estudio de Especies Invasivas, Argentina, utilized the sequence homology method in an effort to discover new viral natural enemies of this ant in Argentina for potential release in the U.S. as control agents. A new virus, Solenopsis invicta 5 (SINV-5) was discovered by these scientists and many new leads for future studies and possible discoveries were identified.

Technical Abstract: Metagenomics and next generation sequencing were employed to discover new virus natural enemies of the fire ant, Solenopsis invicta Buren in its native range (i.e., Formosa, Argentina) with the ultimate goal of testing and releasing new viral pathogens into U.S. S. invicta populations to provide natural, sustainable control of this ant. RNA was purified from worker ants from 182 S. invicta colonies, which was pooled into 4 groups according to location. A gene library was created from each group and sequenced using Illumina Miseq technology. After a series of winnowing methods to remove S. invicta genes, known S. invicta virus genes, and all other non-virus gene sequences, 61,944 unique singletons were identified with virus identity. These were assembled de novo yielding 171 contiguous sequences with significant identity to non-plant virus genes. Fifteen contiguous sequences exhibited very high expression rates and were detected in all four gene libraries. One contig (Contig_29) exhibited the highest expression level overall and across all four gene libraries. Random amplification of cDNA ends analyses expanded this contiguous sequence yielding a complete virus genome, which we have provisionally named Solenopsis invicta virus 5 (SINV-5). SINV-5 is a positive-sense, single-stranded RNA virus with genome characteristics consistent with the Dicistroviridae. The replicative genome strand of SINV-5 was detected in worker ants indicating that S. invicta serves as host for the virus. Many additional sequences were identified that are likely of viral origin. These sequences await further investigation to determine their origins and relationship with S. invicta. This study expands knowledge of the diversity and relative frequencies of RNA sequences associated with the virome of S. invicta.