C4A and viral infectious disease: For example, transgenic Arabidopsis plants expressing beet curly top virus (BCTV) and beet severe curly top virus (BSCTV) C4 exhibit symptoms similar to those cause by the viral infection, which are induced by ectopic cell division [29,30]; the C4 protein of sweet potato leaf curl virus (SPLCV) alters plant development by regulating brassinosteroid signaling through the interaction with AtBIN2 [31]; and tomato leaf curl Yunnan virus (TLCYnV) C4 induces cell division through enhancing the stability of Cyclin D 1.1, which regulates the G1/S-phase transition in plants [32].