Two novel densoviruses from storage pests insects (Zophobas morio and Tenebrio molitor) in Türkiye: Genomic and ultrastructural comparison

Abstract

Densoviruses are small, linear, single-stranded DNA viruses that are 18–28 nm in size and can be filtered. Densoviruses are also known as the ‘black wasting virus' because they cause acute infections in their hosts, causing them to turn black and die. In this study, densoviruses were isolated for the first time from the larvae of the storage pests Tenebrio molitor and Zophobas morio in Türkiye. Although both warehouse pests are consumed as pet food and, in some countries, as human food, they are known to cause respiratory problems such as asthma, anaphylaxis, and separation anxiety. Isolated viruses in this study, named TmDNV-TR and ZmDNV-TR, respectively. Morphological and molecular characterizations of both isolates were performed. Transmission electron microscopy analyses showed that the viruses had a circular inclusion morphology with mean diameters of 22.19 nm (ZmDNV-TR) and 28.95 nm (TmDNV-TR), and TmDNV-TR was significantly larger than ZmDNV-TR. Genomic analysis revealed that the 5467 bp region contained five open reading frames (ORFs) in both viral genomes. The genomic similarity between the isolates was found to be 98.92% and there were amino acid variations, particularly in non-structural 3 (ns3). Interestingly, the phylogenetic tree based on the ZmDNV-TR genome sequence and the results of the Kimura-2 parameter analysis showed a close relationship with a Blattella germenica densovirus. When the genome was digested in silico with restriction enzymes (BsmAI, ApeKI, and BbvI), it was observed that there was an excess of bands in ZmDNV-TR compared to TMDNV-TR for all three enzymes. In this study, for the first time, two different densovirus isolates were obtained from the same insect breeding farm and compared in terms of both structural size and genomics. The spontaneous death of many insects in the breeding farm suggests that this epidemic is vertically transmitted and may be an ideal biological control agent.