An eruption of LTR retrotransposons in the autopolyploid genomes of Chrysanthemum nankingense (Asteraceae)

Abstract

Background Whole genome duplication, associated with the induction of widespread genetic changes, has played an important role in the evolution of many plant taxa. The majority of extant angiosperm species have undergone at least one polyploidization event, forming either an auto- or allopolyploid organism. Compared with allopolyploidization, however, few studies have examined autopolyploidization, and almost no studies have focused on the response of genetic changes to autopolyploidy. Results In the present study, newly synthesized C. nankingense autotetraploids (Asteraceae) were employed to characterize the genome shock following autopolyploidization. Available evidence suggested that the genetic changes primarily involved the loss of old fragments and the gain of novel fragments, and some novel sequences were potential long terminal repeat (LTR) retrotransposons. As Ty1-copia and Ty3-gypsy elements represent the two main superfamilies of LTR retrotransposons, the dynamics of Ty1-copia and Ty3-gypsy were evaluated using RT-PCR, transcriptome sequencing and LTR retrotransposon-based molecular marker techniques. These results suggest that autopolyploidization might also be accompanied by perturbations of LTR retrotransposons, and the emergence retrotransposon insertions might show more rapid homologue divergence, resulting in diploid-like behaviour, potentially accelerating the evolutionary process among progenies. Conclusions Our results strongly suggest a need to expand current evolutionary framework to encompass a genetic dimension when seeking to understand genomic shock following autopolyploidization in Asteraceae.