Characterization of a Novel RNA Virus Discovered in the Autumnal Moth Epirrita autumnata in Sweden

Joachim De Miranda,Jörg Stephan,Olle Terenius,Helena Bylund,Piero Onorati,Olof Karlberg,Harald Hedman

doi:10.3390/v9080214

Joachim De Miranda, Jörg Stephan + Show 5 more

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https://doi.org/10.3390/v9080214

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Abstract

A novel, 10 kb RNA virus—tentatively named ‘Abisko virus’—was discovered in the transcriptome data of a diseased autumnal moth (Epirrita autumnata) larva, as part of a search for the possible causes of the cyclical nature and mortality associated with geometrid moth dynamics and outbreaks in northern Fennoscandia. Abisko virus has a genome organization similar to that of the insect-infecting negeviruses, but phylogenetic and compositional bias analyses also reveal strong affiliations with plant-infecting viruses, such that both the primary host origin and taxonomic identity of the virus remain in doubt. In an extensive set of larval, pupal, and adult autumnal moth and winter moth (Operophtera brumata) outbreak samples, the virus was only detected in a few adult E. autumnata moths as well as the single larval transcriptome. The Abisko virus is therefore unlikely to be a factor in the Fennoscandia geometrid population dynamics.

Highlights

Geometrid moth larvae are major defoliators of deciduous forests in central and northern Europe.In northern Fennoscandia, vast areas of mountain birch forests are recurrently defoliated by larvae of two geometrid species
Analysis of the RNA phase on the other hand revealed in one of the samples an overwhelming abundance of microbial sequences, with 88% of the reads belonging to a 0.8 kb contig with 91% amino acid identity to an Acinetobacter baumannii hypothetical protein (GenBank WP_071209019.1) and 7% of the reads to a single 10 kb RNA virus
Subsequent screening of an extensive set of natural samples revealed that the virus could not be detected in either larvae or pupae of both E. autumnata and O. brumata, and that it could be detected in the 2012–2013 geometrid outbreak in northern Fennoscandia

Summary

Introduction

Geometrid moth larvae are major defoliators of deciduous forests in central and northern Europe. In northern Fennoscandia, vast areas of mountain birch forests are recurrently defoliated by larvae of two geometrid species. The winter moth has started to appear at outbreak densities in locations where the autumnal moth was previously the sole outbreak species, probably due to climate change [1,2]. Both species show cyclical population dynamics with regular density fluctuations at cycles of 9–11 years, the highest seasonal density at any one location and year does not always correspond to an outbreak density. Occasionally diseased autumnal moth larvae have been observed at outbreak density locations, while no diseased winter moth larvae

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