The Distribution, Evolution, Structural Characteristics, and Functional Analysis of the Mariner-Like Elements in Bamboo

Abstract

Most bamboo species are distinguished by the rapid growth, e.g., more than 100 cm/d in Phyllostachys pubescens. The latest research showed that the genome of P. pubescens is large and contains large and diverse families of transposable elements, which were assumed to effect on its morphogenesis and development. Mariner-like elements (MLEs) are class II transposable elements found in almost all eukaryotic genomes. We have characterized 82 amplification fragments and 79 full-length mariner-like transposases representing MLEs derived from 79 representative bamboo species from 38 genera within six subtribes of the Bambusoideae. Phylogenetic analysis of these MLE transposase sequences shows that MLEs are widespread, diverse, and abundant in the Bambusoideae. There is horizontal transfer between distantly related species or an ancestral MLE polymorphism followed by divergent evolution and stochastic loss. Two full-length MLEs were isolated with typical ITR consensus sequences of plant MLEs, intact DNA-binding motifs, and DD39D catalytic domain, and many residues are previously shown to be critical for transposase activity from P. pubescens, implying that both transposons are likely natively active. Transformation into Arabidopsis thaliana showed that the MLE transposons left the primary site, jump, and produce footprints in the A. thaliana genome. The active bamboo Tc1/mariner will provide a foundation for future comparative analyses of animal and plant elements, a new wide host range transposable element available for plant gene tagging.