Abstract：Miniature inverted-repeat transposable elements (MITEs) are the most abundant DNA elements identified in plants genome and involved in many important biological events. However, only few of the MITEs families are confirmed as active transposable elements, which makes it very challenging to study its mechanism. In this study, we aimed to enhance our understanding of MITEs transposition in tobacco(Nicotiana tabacum) plants. Bioinformatics analytical tools, such as MITE-Hunter, Muscle-Multiple Sequence Alignment and TIR/TSD analysis, were employed to study MITEs sequence structural features and copy numbers of tobacco genes from the NCSU database. From almost 2 million publicly available tobacco gene sequences, we were able to reveal 21 different MITEs family (named TMi 1 to TMi 21), in which, 17 of them were reported for the first time in this study and 4 of them were recently reported by other researchers. Amongst all of the newly identified MITEs family, we were particularly interested in TMi 1 family. Identification of TMi 1 element polymorphism in different tobacco strains had provided preliminary evidence of MITEs transposition activity. Moreover, we had established 2 specific biological phenotypes for transposon display assay and the results showed that TMi 1 was an active transposon element. This was the first time which an active MITEs was reported in tobacco genome. For the last 2 decades, MITEs and its transposition activities were studied mainly in rice (Oryza sativa) plant models. This study not only identified new MITEs family, but also validated that tobacco plant was a very useful tool for studying MITEs and its transposition activities. We demonstrated that tobacco genome was a transposon-rich species and potentially possess novel active MITEs elements. Such discovery provides new perspectives and improves our understanding in MITEs transposon and gene regulation. Therefore, further investigation of MITEs activities in tobacco plants is required and possibly will re-define the principal of genome evolution and genetic biodiversity formation.
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