Abstract
Geminiviruses induce severe developmental abnormalities in crops and cause severe economic losses worldwide. Owing to the limited coding capacity of the viral genome, geminiviruses produce a limited number of multifunctional effectors to adapt to the host cellular environment. Among these effectors, the geminivirus-encoded C4/AC4 protein is a powerful viral effector with unexpected versatility. Here, we summarize the current knowledge on this remarkable protein and discuss future work on the C4/AC4 protein to provide new insights into plant-geminivirus interactions and integrated control of diseases induced by them.