Proliferation Cell Nuclear Antigen of Bemisia tabaci facilitates replication and transmission of a bipartite begomovirus

The transmission of plant viruses by insect vectors is a critical determinant of global agricultural losses. For bipartite begomoviruses from the genus Begomovirus, family Geminiviridae, whitefly transmission has long been considered non propagative. This long-standing view, however, lacked direct experimental evidence concerning viral evolution. The fact that the ability of the viruliferous whitefly to transmit the virus throughout the adult lifespan is inconsistent with a non propagative mode of transmission. Recently, replication of a monopartite begomovirus in the whitefly vector Bemisia tabaci has been demonstrated, which contributes to virus persistence and transmission. Here, we hypothesised that a bipartite begomovirus ToLCPalV (tomato leaf curl Palampur virus) could also replicate inside the whitefly to facilitate its transmission.In this study, FISH and strand specific PCR were used on dissected whitefly tissues (midgut and salivary glands) to detect viral replication. Illumina mRNA seq and protein interaction assays were employed to identify whitefly factors including those implicated in DNA repair, replication, as well as antiviral RNA interference pathways. Finally, with functional validation using virus-induced gene silencing, one of these factors PCNA (proliferating cellular nuclear antigen), which was shown to bind the viral proteins AC1 (Replication initiator protein) and AC3 (Replication Enhancer), was downregulated, leading to reduced viral load and transmission.The study reveals that ToLCPalV breaks the conventional non propagative classification by replicating within the whitefly. Evidence further shows that the whitefly replication factor PCNA interacting with viral replication associated proteins facilitates virus replication and transmission.Our results redefine the transmission model of bipartite begomoviruses in whitefly, revealing a propagative transmission strategy and highlighting vector proteins as potential targets to disrupt virus spread and reduce crop losses.