The putative evolutionary relationship among helitron_mc1, helitron_mc2 and ZmhelA5. A. Structural information of three helitrons identified in the maize genome. The size of helitron_mc1, helitron_mc2 and ZmhelA5 were 1,617 bp, 2,683 bp and 1,111 bp, respectively. Sequences between two lines had identities ≥ 85%. B, C and D. The hypothesized evolutionary path for helitron with multiple 3' termini. B. zmhelA5 inserted into helitron_hypo2 to form new helitron. Then new helitron_hypo2 inserted into helitron_mc1 (hel1) to form the C state. C to D: The nested intermediate helitron transposed starting from the 5'-terminus of ZmhelA5 to generate helitron_mc2 with three 3'-termini, leaving a remnant with two 5'-termini.
Dong et al. BMC Genomics 2011 12:609 doi:10.1186/1471-2164-12-609