Transposable Element Exaptation in Plants

Abstract

While evolution is often understood exclusively in terms of adaptation, innovation often begins when a feature adapted for one function is co-opted for a different purpose, such as when feathers originally adapted for insulation became used for flight. Co-opted features are called exaptations. Transposable elements are often viewed as molecular parasites, yet they are frequently the source of evolutionary innovation. One way in which transposable elements contribute to evolution is that their sequences can be co-opted to perform phenotypically beneficial functions. Transposable element gene exaptations have contributed to major innovations such as the vertebrate adaptive immune system and the mammalian placenta. They also often become transcription factors, and transposable element-derived transcription factor binding sites can form new regulatory networks. In this chapter, we review transposable element coding sequence exaptations in plants.