Transposition of a Rice Mutator-like Element in Yeast

Mutator-like transposable elements (MULEs) are widespread in plants and well-known for their high transposition activity as well as their capability to duplicate and amplify host gene fragments. Despite their abundance and importance, few active MULEs have been identified and there is no report of MULE activity in non-native hosts. In this study, we demonstrated that a rice MULE, Os3378, is capable of excising and reinserting in yeast, suggesting that yeast harbors all the host factors for transposition of MULEs. The transposition activity induced by the wild-type transpose is low but can be altered through modification of the transposase sequence including deletion, fusion, and substitution. We identified a critical region in the transposase where the net charge and hydropathy of the amino acids seem to be important for the activity. Moreover, the excision frequency is dependent on the size of the non-autonomous element. In addition to the potential application in functional genomics, this study provides the foundation for further studying the transposition mechanism of MULEs as well as their acquisition and duplication of genomic sequences.