A nuclear protein that binds specifically to several maize transposons is not essential for Ds1 excision

Specific binding of plant nuclear proteins to GGTAAA-like motifs in the ter minal regions of the transposable elements Ac and Mul has been detected in several laboratories. However, the role of these proteins in transposition remains unknown. To test the hypothesis that this binding activity is neces sary for transposition, we identified and mutagenized all the binding motif s within the Dsl element. This analysis enabled us to define more precisely the requirements for binding of the host protein. We then tested the abili ty of the mutated elements to excise from the maize streak virus (MSV) geno me. We found that mutated Dsl elements that do not bind the host proteins, as determined by gel-shift competition assay, are still capable of undergoi ng excision in maize, although for one of the maize lines the rate of excis ion was reduced. Excision of mutated Dsl elements generated typical excisio n footprints. These data indicate that binding of host protein(s) to the GG TAAA-like motifs is not essential for Dsl excision; however, it may contrib ute to the efficiency of the process.