MAP2K2 and viral infectious disease: Knocking out two components of this cascade, MKK2 or MPK4 in tobacco renders the plant more susceptible to geminivirus infection and virus infection of geminivirus without betasatellite induced typical virus symptom in MKK2 or MPK4 knockout tobacco, indicating that MKK2 or MPK4 mutant can complement the lack of βC1 in virus infection.