Activation of Ty1-copia Group Retrotransposons of Dendrobium officinale under Abiotic Stress Conditions

By using universal primer Ty1-copia retrotransposon reverse transcriptase (RT), the conserved reverse transcriptase domain of about 260 bp, which was induced by cold stress and osmotic stress, was amplified by RTPCR from the Dendrobium officinale in this study, indicating that the retrotransposon could be activated by stress conditions. The amplicons were recovered and cloned for sequencing and analyzing by related bioinformatics software. 78 Ty1-copia like retrotransposon RTs transcriptionally activated were obtained with high heterogeneity. The length of these sequences varied from 245 to 265 bp, all the sequences were rich in AT and homology ranged from 42.9% to 99.2%. The same to Ty1-copia like retrotransposon RT of genome, different cis-acting regulatory elements induced by stress conditions and the starting transcription signals, corresponding to CAAT box, TATA box conserved sequences and some other regulatory elements. The cis-acting regulatory elements induced by stress conditions of reverse transcriptase transcriptionally activated of Ty1-copia retrotransposons were significantly increased than Ty1-copia like retrotransposon RT of genome. When translated into amino acids, some sequences presented stop codon mutation or/and frameshift mutation, and all sequences presented mutation in conserved sequence "SLYGKQ". Four categories were identified through phylogenic analysis after alignment analyses of their amino acid sequences, and with Ty1-copia like retrotransposon RT of genome having low homology, which indicated that reverse transcriptase transcriptionally activated of Ty1-copia retrotransposons, which induced under stress conditions, had significantly differences with Ty1-copia like retrotransposon RT of genome.