DETERMINATION OF THE ORIGIN CLEAVAGE AND JOINING DOMAIN OF GEMINIVIRUS REP PROTEINS

Replication of the single-stranded DNA genome of plant geminiviruses f ollows a rolling circle mechanism. It strictly depends on a 'rolling c ircle replication initiator protein', the M(r) 41 kDa viral Rep protei n, encoded by the C1 or AC1 genes. Using wheat dwarf virus (WDV) and t omato yellow leaf curl virus (TYLCV) as examples, we show that not onl y the full-size Rep proteins, but also a putative 30 kDa translation p roduct of WDV open reading frame C1-N as well as an artificially short ened 24 kDa Rep of TYLCV, cleave and join single-stranded origin DNA i n vitro. Thus the pivotal origin recognition and processing activities of geminivirus Rep proteins must be mediated by the amino-terminal do main of Rep.