A gene of rice has homology to SEQ. ID NO.:2, and a transposase gene of rice has homology to bases 3190-4557 of SEQ. ID NO.:2, or encodes SEQ. ID NO.:4, or variants thereof, plasmids and transformants thereof as well as plasmids and transformants thereof. A transposase has SEQ. ID NO.:4, or a variant thereof. A method of transposing a transposon gene of rice (Oryza sativa) having homology to SEQ. ID NO.:1 comprises transducing a transposon gene of rice having homology to SEQ. ID NO,:2, or a transposase gene of rice encoding a protein comprising SEQ. ID NO.:4 or a variant thereof.