A Gaijin-like MITE Is Mobilized In Rice Received γ-ray Irradiation

Miniature inverted-repeat transposable elements (MITEs) are one type of transposable elements (TEs), which are largely found in eukaryotic genomes and involved in a wide variety of biological events. MITEs are closely associated with euchromatic genes and have been exploited as a genetic tool for plant genome analyses, but their physiological function remains largely unknown. Our previous study identified amplicons discrepancy in the gene of a putative leucine-rich repeat protein (PLRRP) in rice and mGing, a member of Gaijin-like MITEs, was associated in this phenomenon. Firstly, we studied a series of bioinformaitic analyses on the structural characters of this family and its copy number in genomes of different rice subspecies and Arabidopsis. Secondly, based on the observation that mGing showed different copy number in two rice genomes, and its absence at PLRRP gene locus in some rice cultivars and wild rice accessions, we hypothesized that mGing might remain active transposition ability. This study was aimed to investigate the current mGing transposition in rice. Transposon display (TD) assay showed that mGing was actively transposed in genomes of rice seedlings germinated from seeds with high dose y-irradiation. The observed active transposition in TD assay was then confirmed by PCR validation and sequencing. Sequence alignment and comparison analyses showed that many single nucleotide polymorphisms (SNPs) were generated at the transposition sites post mGing transposition, which implies that MITE insertion may not be a random event and possibly is associated with inaccurate DNA replication. In addition, the band polymorphism of mGing in different rice cultivars and wild rice accessions from the same planting region suggested that mGing had transposed during rice evolution. In summary, this study for the first time clearly demonstrated that mGing is actively transposed under stress condition in rice and provides a foundation for further in-depth analysis of the roles of MITEs in biological processes.