Begomoviral βC1 orchestrates organellar genomic instability to augment viral infection.

Chloroplast is the site for transforming light energy to chemical energy. It also acts as a production unit for a variety of defense-related molecules. These defense moieties are necessary to mount a successful counter defense against pathogens, including viruses. Previous studies indicated disruption of chloroplast homeostasis as a basic strategy of Begomovirus for its successful infection leading to the production of vein-clearing, mosaic, and chlorotic symptoms in infected plants. Although begomoviral pathogenicity determinant protein Beta C1 (βC1) was implicated for pathogenicity, the underlying mechanism was unclear. Here we show that, begomoviral βC1 directly interferes with the host plastid homeostasis. βC1 induced DPD1, an organelle-specific nuclease, implicated in nutrient salvage and senescence, as well as modulated the function of a major plastid genome maintainer protein RecA1, to subvert plastid genome. We show that βC1 was able to physically interact with bacterial RecA and its plant homolog RecA1, resulting in its altered activity. We observed that knocking-down DPD1 during virus infection significantly reduced virus-induced necrosis. These results indicate the presence of a strategy in which a viral protein alters host defense by targeting modulators of chloroplast DNA. We predict that the mechanism identified here might have similarities in other plant-pathogen interactions.