Poster: Evolution

Abs # 785: Ping is an autonomous element that is required for mPing transposition in rice anther culture

Presenter:	Kazuhiro, Kikuchi , kikuchi@nibb.ac.jp
Authors	Kazuhiro, Kikuchi  (A)   Wada, Masamitsu  (A) (B)  Hirano, Hiroyuki  (C)
Affiliations:	(A): National Institute of Basic Biology (B): Tokyo Metropolitan University (C): The University of Tokyo

Miniature inverted-repeat transposable elements (MITEs), one of the major groups of transposable elements (TEs), are ubiquitously distributed in the genomes of plants and animals, and contribute to evolution and diversification of genomes. mPing is a MITE found in the rice genome, which is a 430-bp element with terminal inverted repeat (TIR) of 15 bp. We have found that mPing is activated and mobilized at a high frequency in anther culture (Kikuchi et al. Nature 421: 167-170, 2003). We also identified two putative autonomous elements, Ping and Pong, of which TIRs show high similarity with that of mPing and have putative transposases. We have tried to reveal which element is responsible for mPing transposition in anther culture. Southern blot analysis showed that a Ping element was present only in the japonica (a subspecies of rice) genomes except for a strain, Taichung 65 (T65), but not in the indica genomes. Pong elements were contained in the both japonica and indica genomes. It was revealed that Ping elements were frequently excised from their original sites in japonica rice by anther culture, but they were not excised in T65. By contrast, mPing elements were activated and mobilized when a Ping element was introduced in T65 by agrobacterium-mediated transformation. Next, we examined the mobility of mPing using reciprocal chromosomal substitution lines of japonica (Asominori) and indica (IR24). The results clearly showed that mPing elements were mobile in the strains carrying a chromosome segment derived from Asominori, which contained a Ping element, but they are not mobile in the strain that lack the element. These results clearly indicated that Ping, but not Pong, is responsible for transposition of mPing during anther culture.