A transposition-active Phyllostachys edulis long terminal repeat (LTR) retrotransposon

Due to infrequent sexual reproduction, moso bamboo breeding by hybridization is extremely technically difficult. Insertional mutagenesis based on endogenous active transposons may thus serve as an alternative method to create new germplasm of moso bamboo. In the present study, using LTR-STRUC, a full-length intact long terminal repeat (LTR) retrotransposon was identified in the moso bamboo genome and was named PHRE2 (Phyllostachys edulis retrotransposon 2). The 5' and 3' LTR sequences of PHRE2 were highly (98.39%) similar. PHRE2 contains all domains necessary for transposition such as gag, pr, rt, rh, and int. The coding frames of these essential domains were complete and had no apparent mutations. In addition, PHRE2 possessed a prime binding site (PBS), a polypurine tract (PPT), and two typical sequences of LTR retrotransposons. A genome-wide scan showed that the moso bamboo genome has only one full-length sequence of PHYRE2. After its transfer to Arabidopsis thaliana, an increase in PHRE2 copy number occurred in the T-3 plants compared to in the T-2 plants. After moso bamboo seedlings were grown in tissue culture or treated by irradiation or plant hormones, the copy number of PHRE2 significantly increased. These findings indicate that PHRE2 has the capacity for transposition, which can be induced by environmental conditions.