Evolutionary features of new picorna-like viruses in Culex (Melanoconion) mosquitoes

In this study, we investigated unclassified picorna-like viruses in <i>Culex</i> (<i>Melanoconion</i>) mosquitoes from São Paulo, Brazil, an area of high mosquito biodiversity and arbovirus activity. Two mosquito pools were processed using next-generation sequencing (NGS), and datasets were analyzed <i>via de novo</i> assembly to reconstruct viral genomes and assess evolutionary relationships. We identified two highly similar viral genomes, named <i>Culex</i> (<i>Melanoconion</i>) picorna-like virus, CmV_B38 and CmV_B39, exhibiting 99.93% nucleotide identity, both of which encode a three-domain replication block characteristic of viruses within the order <i>Picornavirales</i>. Phylogenetic reconstruction based on the RNA-dependent RNA polymerase (RdRp) gene revealed that these viruses form a distinct, previously undescribed clade, most closely related to Yongsan picorna-like virus 4 and several other unclassified viruses that have been reported predominantly in Asian regions. These findings may indicate possible geographical connectivity or convergence in viral evolution across distinct ecosystems. Notably, the results highlight the underexplored diversity of insect-specific viruses, particularly those associated with mosquito vectors. Furthermore, the data are consistent with the hypothesis that ecological factors and host specificity could influence the evolutionary dynamics of these viral lineages. The study not only enhances our understanding of the mosquito-associated virome but also emphasizes the critical need for ongoing viral surveillance, especially in biodiverse regions. Such efforts are essential for elucidating the evolutionary dynamics of RNA viruses and for anticipating the emergence of novel viral pathogens that may pose future risks to public health or agriculture.