Silencing of the Prophenoloxidase Gene Increased the Ability of Acquisition and Retention of Tomato chlorosis virus by .

Tomato chlorosis virus (ToCV) has seriously impacted tomato production around the world. ToCV is semi-persistently transmitted by the whitefly, , 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 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 , we cloned the complete Open Reading Frames (ORF) of the s ( and ), and then structure and phylogenetic analyses were performed. s 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 s were expressed in all tissues and developmental stages. We found that only was significantly upregulated after acquired ToCV for 12 and 24 h. According to the paraffin-fluorescence probe-fluorescence in situ hybridization (FISH) experiment, we verified that ToCV and were co-located in the thorax of , which further revealed the location of their interaction. Finally, the effects of the s on ToCV acquisition and retention by were determined using RNA interference (RNAi). The results showed that the RNAi of the responsive gene () significantly increased the titer of ToCV in . These results demonstrate that participates in ToCV acquisition and retention by .