A moso bamboo (Phyllostachys edulis) miniature inverted-repeat transposable element (MITE): the possible role of a suppressor

Transposable elements (transposons) are fragments of DNA sequences which can move within host genome. Miniature inverted-repeat transposable elements (MITEs) are widespread and high-copy transposable elements in eukaryotic genomes. Tourist-like MITEs are especially abundant in plant kingdom. Earlier genome-wide analysis has shown that MITEs are widely distributed in the moso bamboo genome and preferentially inserted into gene regions. In the present study, in order to examine the potential influence of MITEs on the moso bamboo gene expressions, a highly conserved Tourist-like MITE family, which distributed near genes, was selected as research focus and named PhTst-3 (Phyllostachys edulis Tourist-like element 3). The MITEs’ insertion sites were tested in moso bamboo half-sib seedlings by real-time fluorescence quantitative PCR. Amplification polymorphisms were found in a copy of PhTst-3 (PhTst-3-55) which was located in the intron of PH01002699G0010. This inserted PhTst-3-55 had a significant impact on the gene expression revealed by the real-time fluorescence quantitative PCR. The gene expression levels were four times higher in the absence of PhTst-3-55 than those in the presence of it. This finding suggests that the PhTst-3 located in the intron is involved in the regulation of the gene. In order to examine the impact of PhTst-3-55 on the near genes, the PhTst-3-55 was inserted into a promoter analysis vector, pxk7S2D, between the two promoter sequences. The Agrobacterium-mediated transient expression showed that PhTst-3-55 insertion decreases the expression level of upstream GUS gene and downstream GFP gene. So, PhTst-3-55 can have a silencing role by bidirectionally inhibiting gene expression.