Genome sequence and organization of the Mythimna (formerly Pseudaletia) unipuncta granulovirus Hawaiian strain

Yinü Li,Ping Tang,Xingjian Liu,Qilian Qin,Huan Zhang,Zhifang Zhang

doi:10.1038/s41598-020-80117-3

Abstract

Purified occlusion bodies (OBs) of Mythimna (formerly Pseudaletia) unipuncta (the true armyworm) granulovirus Hawaiian strain (MyunGV-A) were observed, showing typical GV morphological characteristics under scanning and transmission electron microscopy (EM). The genome of MyunGV-A was completely sequenced and analysed. The genome is 176,677 bp in size, with a G+C content of 39.79%. It contains 183 open reading frames (ORFs) encoding 50 or more amino acids with minimal overlap. Comparison of MyunGV-A with TnGV, XcGV, and HearGV genomes revealed extensive sequence similarity and collinearity, and the four genomes contain the same nine homologous regions (hrs) with conserved structures and locations. Three unique genes, 12 baculovirus repeated ORF (bro), 2 helicase, and 3 enhancin genes, were identified. In particular, two repeated genes (ORF39 and 49) are present in the genome, in reverse and complementarily orientations. Twenty-four OB proteins were identified from the putative protein database of MyunGV-A. In addition, MyunGV-A belongs to the Betabaculovirus group and is most closely related to TnGV (99% amino acid identity) according to a phylogenetic tree based on the combined amino acid sequences of 38 core gene contents.

Highlights

Baculoviruses are a large family of rod-shaped, invertebrate-infecting viruses with large circular, covalently closed, double-stranded DNA genomes of between 80 and 180 kb
We present the complete sequence and organization of the MyunGV-A genome and compare it with other baculoviruses by genomic and phylogenetic analysis
scanning electron microscopy (SEM) revealed that the purified occlusion bodies (OBs) of MyunGV-A have elongated ellipse shapes, with a length of approximately 0.5 μm and a width of approximately 0.3 μm (Fig. 1A)

Summary

Introduction

Baculoviruses are a large family of rod-shaped, invertebrate-infecting viruses with large circular, covalently closed, double-stranded DNA genomes of between 80 and 180 kb. This family was initially taxonomically subdivided into nucleopolyhedroviruses (NPVs) or granuloviruses (GVs) based on viral occlusion morphology[1]. When an increasing number of genome sequences became available, it was clear that lepidopteran NPVs and GVs are more closely related to each other than to dipteran and hymenopteran NPVs. a new taxonomic division that follows the evolution of the host more c losely[2] was accepted by the International Committee on Taxonomy of Virus (ICTV).

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Results

Conclusion