Abstract: Cucumber mosaic virus（CMV） has a very wide host range and a world\|wide distribution; it can cause significant economic losses in many vegetables and horticultural crops. CMV strains or isolates could be classified into subgroups IA， IB and II. CMV 2b protein was an important virulence factor and one of the firstly identified RNA\|silencing suppressors， and the 2b proteins encoded by subgroup I CMV strains could interact itself in planta. However， it remains unknown whether the 2b proteins encoded by subgroup II strains could interact itself in planta. Results from the bi\|molecular fluorescence complement （BiFC） experiments showed that 2b protein encoded by subgroup II strain LS did not interact itself. Subsequently， we exchanged sequences between Fny2b and LS2b， then found that the N\|terminal 13\|37amino\|acid sequence of CMV 2b was the key functional domain， which was associated with the self\|interaction of CMV 2b protein.

Key words:  cucumber mosaic virus, 2b protein, self\, interaction, functional domain