Complete genome sequence of a novel nege-like virus in aphids (genus Indomegoura)

Aphids are important vectors of numerous plant viruses. Besides plant viruses, a number of insect specific viruses (ISVs), such as nege/nege-like viruses, have been recently discovered in aphids of the genera Aphis, Rhopalosiphum, and Sitobion. In this study, the complete genome sequence of a novel nege-like virus, tentatively named "Indomegoura nege-like virus 1" (INLV1), was identified in aphids of the genus Indomegoura. INLV1 possessed a single positive-stranded RNA genome with 8945 nucleotides, which was predicted to contain three typical open reading frames (ORFs) of negeviruses (including ORF1, ORF2, and ORF3), a 44-nt 5' untranslated region (UTR) and a 98-nt 3' UTR. Five conserved domains were predicted for INLV1, including an Alphavirus-like methyltransferase domain, a RNA virus helicase core domain, and a RNA-dependent RNA polymerase domain (RdRP) in ORF1, a DISB-ORF2_chro domain in ORF2, and a SP24 domain in ORF3. According to the maximum likelihood phylogenetic tree based on RdRP, INLV1 was grouped with barley aphid RNA virus 1 and Hubei virga-like virus 4, together with another two invertebrate viruses, which formed a distinct clade in the proposed group Centivirus. The alignment of RdRP domains for INLV1 and other nege/kita-like viruses suggested that RdRP of INLV1 contained the permuted C (GDD)- A [DX(4-5)D] -B [GX(2-3)TX(3)N] motifs, which were conserved in the Centivirus and Sandewavirus groups. Furthermore, the high abundance and typical characteristics of INLV1 derived small interfering RNAs clearly showed the active replication of INLV1 in the aphid Indomegoura. INLV1 is the first nege-like virus infecting aphids of the genus Indomegoura. As far as we know, it is also the first ISV revealed in this aphid genus.