Plasticity of the lettuce infectious yellows virus minor coat protein (CPm) in mediating the foregut retention and transmission of a chimeric CPm mutant by whitefly vectors

Conserved untranslated regions of multipartite viruses: Natural markers of novel viral genomic components and tags of viral evolution

Viruses with split genomes are classified as being either segmented or multipartite based on whether their genomic segments occur within a single virion or across different virions. Despite variations in number and sequence during evolution, the genomic segments of many viruses are conserved within the untranslated regions (UTRs). In this study, we present a methodology that combines RNA sequencing with iterative BLASTn of UTRs (https://github.com/qq371260/Iterative-blast-v.1.0) to identify new viral genomic segments. Some novel multipartite-like viruses related to the phylum Kitrinoviricota were annotated using sequencing data from field plant samples and public databases. We identified potentially plant-infecting jingmen-related viruses (order Amarillovirales) and jivi-related viruses (order Martellivirales) with at least six genomic components. The number of RNA molecules associated with a genome of the novel viruses in the families Closteroviridae, Kitaviridae, and Virgaviridae within the order Martellivirales reached five. Several of these viruses seem to represent new taxa at the subgenus, genus, and family levels. The diversity of novel genomic components and the multiple duplication of proteins or protein domains within single or multiple genomic components emphasize the evolutionary roles of genetic recombination (horizontal gene transfer), reassortment, and deletion. The relatively conserved UTRs at the genome level might explain the relationships between monopartite and multipartite viruses, as well as how subviral agents such as defective RNAs and satellite viruses can coexist with their helper viruses.

Silencing of the Prophenoloxidase Gene BtPPO1 Increased the Ability of Acquisition and Retention of Tomato chlorosis virus by Bemisia tabaci

Tomato chlorosis virus (ToCV) has seriously impacted tomato production around the world. ToCV is semi-persistently transmitted by the whitefly, Bemisia tabaci, which is a serious agricultural pest in the world. However, the interaction mechanism between ToCV and its whitefly vector is still poorly understood. Our previous transcriptome analysis demonstrated that the expression level of an immune-related gene, prophenoloxidase (PPO), in B. tabaci increased after ToCV acquisition, which indicates that the PPO may be involved in the interaction mechanism between the ToCV and its vector. To determine the role of the PPO in the acquisition and retention of ToCV by B. tabaci, we cloned the complete Open Reading Frames (ORF) of the BtPPOs (BtPPO1 and BtPPO2), and then structure and phylogenetic analyses were performed. BtPPOs were closely related to the PPO genes of Hemiptera insects. Spatial-temporal expression detection was qualified by using reverse transcription quantitative PCR (RT-qPCR), and this revealed that BtPPOs were expressed in all tissues and developmental stages. We found that only BtPPO1 was significantly upregulated after B. tabaci acquired ToCV for 12 and 24 h. According to the paraffin-fluorescence probe-fluorescence in situ hybridization (FISH) experiment, we verified that ToCV and BtPPO1 were co-located in the thorax of B. tabaci, which further revealed the location of their interaction. Finally, the effects of the BtPPOs on ToCV acquisition and retention by B. tabaci were determined using RNA interference (RNAi). The results showed that the RNAi of the responsive gene (BtPPO1) significantly increased the titer of ToCV in B. tabaci. These results demonstrate that BtPPO1 participates in ToCV acquisition and retention by B. tabaci.