Analysis of the chromatin binding af?nity of retrotransposases reveals novel roles in diploid and tetraploid cotton

LTR-retrotransposable elements are major components of diploid(Gossypium arboreum) and tetraploid(Gossypium hirsutum) cotton genomes that have undergone dramatic increases in copy number during the course of evolution. However, little is known about the biological functions of LTR-retrotransposable elements in cotton. Here, we show that a copia-like LTRretrotransposable element has maintained considerable activity in both G. arboreum and G. hirsutum. We identified two functional domains of the retrotransposon and analyzed their expression levels in various cotton tissues, including leaves, ovules, and germinating seeds.ChIP-qPCR(chromatin immunoprecipitation followed by quantitative PCR), using a copia-specific antibody,established that copia-like proteins primarily bind to the first exons of several protein-coding genes in cotton cells. This finding suggests that retrotransposons play a novel, important role in regulating the transcriptional activities of protein-coding genes with various biological activities.