On the Origin of Burst of MITE Element mPing in Rice Population

Transposable elements occupy substantial proportion of eukaryotic genomes. Their movements are sources of genetic innovations. Miniature Inverted-repeat Transposable Elements (MITEs) are deletion derivatives of autonomous DNA transposons and in great abundance in plant genomes. MITE element mPing is an active transposon in rice and has amplified to high copy number in several rice strains. The insertion sites of mPing are highly associated with protein-coding genes and contribute to innovation of regulatory network of nearby genes in rice. However, the mechanism of how mPing amplification is activated in rice population is not fully understood. In this study, we have characterized the copy number of mPing elements and their autonomous elements Ping and Pong in rice population. The amplification of mPing in temperate japonica rice is associated with amplification of Ping elements in the same group of rice. Particularly, a special Ping locus that inserted in another transposable element is shared in strains carrying high copy number of mPing and associated with high copy number of mPing in rice population, suggesting its role in accumulation of mPing and Ping in rice genome. We will also discuss the dynamics of mPing burst in rice and wild rice genomes and their implications to rice genome evolution.