Thongda, W. | bioRxiv Science

bioRxiv2023

Circular viral copy DNA of Dengue virus (DENV-2) isolated from infected mosquito cell cultures

Dengue virus serotype 2 (DENV-2) is a mosquito-borne disease in the family Flaviviridae. It has been previously shown that DENV-2 can infect C6/36 mosquito cells and cause initial cytopathic effects that dissipate upon serial split-passage to yield persistently infected cultures with normal growth and morphology. In other words, the cell line accommodated persistent DENV-2 infections. It has recently been found that insect viral infections induce the production of viral copy DNA (vcDNA) fragments via host reverse transcriptase (RT). The vcDNA occurs in both linear (lvcDNA) and circular (cvcDNA) forms and produces small interfering RNA (siRNA) transcripts that can result in an immediate protective RNA interference (RNAi) response. The vcDNA can lead to the host acquiring endogenous viral elements (EVE) in genomic DNA. Thus, we hypothesized that DENV-2 cvcDNA and DENV-2-EVE would arise in C6/36 insect cells challenged with DENV-2 virus in vitro. Here we describe the successful isolation and characterization of cvcDNA constructs homologous to DENV-2 from laboratory challenges with C6/36 cells. At least 1 of these appeared to arise from a DENV-2-EVE. We also show that a cvcDNA preparation derived from the DENV-2 infected in C6/36 insect cells and subjected to rolling circle amplification (RCA) significantly reduced DENV-2 replication when applied to naive C6/36 cells prior to the DENV-2 challenge. This preliminary work lays the groundwork for further studies using the C6/36 cell model to screen and characterize protective EVE against insect and shrimp viruses.

microbiology↗

bioRxiv2021

Complex introgression among three diverged largemouth bass lineages

Hybrid zones between diverged lineages offer an unique opportunity to study evolutionary processes related to speciation. Natural and anthropogenic hybridization in the black basses (Micropterus spp.) is well documented, including an extensive intergrade zone between the widespread northern Largemouth Bass (M. salmoides) and the Florida Bass (M. floridanus). Phenotypic surveys have identified an estuarine population of Largemouth Bass (M. salmoides) in the Mobile-Tensaw Delta, with larger relative weight and smaller adult size compared to inland populations, suggesting a potential third lineage of largemouth bass. To determine the evolutionary relationships between these Mobile Delta bass populations, M. salmoides, and M. floridanus, putative pure and intergrade populations of all three groups were sampled across the eastern United States. Phylogenetic analyses of 8,582 nuclear SNPs derived from genotype-by-sequencing and the ND2 mitochondrial gene determined that Delta bass populations stem from a recently diverged lineage of Largemouth Bass. Using a novel quantitative pipeline, a panel of 73 diagnostic SNPs was developed for the three lineages, evaluated for accuracy, and then used to screen 881 samples from 52 sites for genetic integrity and hybridization on the Agena MassARRAY platform. These results strongly support a redrawing of native ranges for both the intergrade zone and M. floridanus, which has significant implications for current fisheries management. Furthermore, Delta bass ancestry was shown to contribute significantly to the previously described intergrade zone between northern Largemouth Bass and Florida Bass, suggesting a more complex pattern of secondary contact and introgression among these diverged Micropterus lineages.

evolutionary biology↗