Amplification of miniature inverted-repeat transposable elements and the associated impact on gene regulation and alternative splicing in mulberry (Morus notabilis)

Abstract

Background: Miniature inverted-repeat transposable elements (MITEs) are common in eukaryotic genomes, and are important for genomic evolution. Results: In the present study, the identification of MITEs in the mulberry genome revealed 286,122 MITE-related sequences, including 90,789 full-length elements. The amplification of mulberry MITEs and the influence of MITEs on the evolution of the mulberry genome were analyzed. The timing of MITE amplifications varied considerably among the various MITE families. Fifty-one MITE families have undergone a single round of amplification, while the other families developed from multiple amplifications. Most mulberry MITEs were inserted near genes and some could regulate gene expression through small RNAs. An analysis of transgenic plants indicated that MITE insertions can upregulate the expression of a target gene. Moreover, MITEs are frequently associated with alternative splicing events (exonizations). Conclusion: The data presented herein provide insights into the generation of MITEs as well as their impact on gene regulation and evolution in mulberry.