Abstract:

Objective: A transposon is a repeat fragment of DNA that can jump in the genome of an organism. According to the mechanism of transposition, transposons are divided into retrotransposons with "copy-paste" mode and DNA transposons with "cut-paste" mode. According to the integrity of the structure, the transposon can be classified into autonomous transposon and non-autonomous transposon. The autonomous transposon has a complete transposase and can independently produce transposase. The transposase of the non-autonomous transposon is incomplete, but contain necessary transpositional elements. The non-autonomous transposon can transpose under the assistance of the transposase from the autonomic transposon. Mariner-like element(MLE) is a kind of DNA transposons that are widely distributed in eukaryotic genomes, with the transposition mode of "cut-and-paste". Previous studies have shown that MLE transposons have great application in the fields of transgene, gene function analysis, gene therapy and so on. In order to reveal the distribution pattern and evolution dynamics of MLE transposons in the evolution of Phyllostachys edulis, the genome-wide mining of the MLE transposons in P. edulis genome were conducted. The distribution and deletion characteristics of autonomous MLE and non-autonomous MLE in the P. edulis genome were studied. Method: Utilization of the MLE transposon sequences of rice, soybeans and P. edulis, with the IRF, Blast and Fasta software, according to the specificity of TIR (Terminal Inverted Repeats) of MLE transposon and its encoding enzyme, the full-length intact MLE transposons were identified in P. edulis genome. According to TIR of the full-length intact MLE transposons, the corresponding non-autonomic MLEs were characterized. The distribution characteristics of autonomous and non-autonomous MLEs and the deletion patterns of non-autonomic MLE structures were analyzed. Result: Two intact autonomous MLE, PhV2MLE1A and PhV2MLE2A, were identified in this study. PhV2MLE1A is 3 950 bp in length, encodes 414 amino acids, and has a 30 bp length TIR. PhV2MLE2A was 12 990 bp, encodes 373 amino acids, and has 49 bp length TIR. According to the similarity of the TIR structure, two non-autonomous transposons corresponding to two autonomous MLEs were identified. In this experiment, two autonomous MLEs with complete structures and their corresponding non-autonomous transposons were obtained. At the same time, it was found that the structural deletion of different non-autonomous transposons was irregular. The distribution of MLE in the P. edulis was random, and the insertion preference was between the conservative sequence TA. Conclusion: A large number of MLE transposons were distributed in the genome of P. edulis. Most of MLE transposons lost their transposable activity due to the lack of transposases in the evolutionary process.

Key words: Phyllostachys edulis, MLE transposon, evolution, deletion mode