Betasatellite: A Hijacker of Plant Innate Immunity

Betasatellites associated with begomoviruses significantly exacerbate viral infections in economically important crops, prompting the evolution of various plant defense mechanisms, including RNA interference, phytohormone signalling and cellular modifications using autophagy and ubiquitination. Approximately 13.5-kDa βC1 protein has two key functions: It boosts viral replication and weakens plant defenses. By interfering with signal transduction pathways and RNA silencing, it makes the plant more vulnerable to infection. Additionally, βC1 impairs chloroplast function, complicating the plant's defense strategies. In contrast, the nuclear shuttle protein (βV1) protein, though less understood, appears to facilitate viral replication and interacts with the helper virus replication enhancer protein (REn), leading to altered localization within the cell. As only 40% of betasatellites encode the βV1 protein, further investigation into its molecular interactions and functions could provide crucial insights for developing effective antiviral strategies against geminivirus infections. This review highlights the complex interplay between betasatellites and host defenses, offering avenues for future research in crop protection.