Isolation And Characterization Of Reverse Transcriptase Fragments Of LTR Retrotransposons From The Genome Of Tamarix Chinensis L.

LTR Retrotransposons play an important role in the abundance,evolution,structure and function of plant genomes.Tamarix chinensis is one of the most excellent ecological restoration plants with saline-alkali and drought tolerance,but its retrotransposons are rarely studied.In this experiment,Tamarix chinensis was used as the experimental material.The leaf genomic DNA was extracted by modified CTAB method,and PCR productions with degenerate primers were sent to the company for amplicon sequencing.93602 RT sequences of Ty1-copia transposons and 121185 RT sequences of Ty3-gypsy retrotransposons were obtained.After screening,the sequence was clustered with 93% similarity.629 RT nucleotide sequences of Ty1-copia transposons were finally obtained,named TCcopia1 ~ TCcopia629;There are 607 RT nucleotide sequences of Ty3-gypsy retrotransposons,named TCgypsy1 ~TCgypsy607.The length of Ty1-copia retrotransposon RT sequences were 261 bp ~291bp,and the length of the Ty3-gypsy retrotransposon RT sequences were 390 bp ~474bp.Both of them were rich in AT sequences.The AT/GC values of the Ty1-copia retrotransposon RT sequences were 1.09 ~ 2.43,and the AT/GC values of the Ty3-gypsy retrotransposon RT sequences were 0.98 ~ 2.48.Sequence homology analysis showed that the similarities of Ty1-copia retrotransposon RT sequences were ranged from 21.01% to 92.83%,meanwhile,Ty3-gypsy retrotransposon RT sequences were ranged from 17.98% to92.80%;Among them,420 sequences in Ty1-copia retrotransposonsand 486 sequences in Ty3-gypsy retrotransposons contained stop codons,which may be the reason for the highly heterogeneity of LTR retrotransposons in Tamarix chinensisThe RT amino acid sequences of Ty1-copia retrotransposon withoutstop s condons contained four conserved domains: "QMDVKT","YVDDM","FLNGDL" and "SLYGLKQA";The RT amino acid sequences of Ty3-gypsy retrotransposon without stop codons contained five conserved domains: "MCVDY","LYAKLXKC","KTAFRT","DLRSGYHQ" and "VMPFGLTNAP".Ty1-copia retrotransposons were mainly distributed in four families,namely Angela,Ale,Ivana and TAR,and TAR family contained the highest numbers of transposons.The Ty3-gypsy retrotransposons were mainly distributed in three families,namely Del,Reina and CRM.The Del family and Reina family were the main components of Ty3-gypsy retrotransposons.Some of the retrotransposons of Tamarix chinensis were closed to Solanum tuberosum and Solanum pinnatisectum,and may have undergone horizontal transfer.These results contributs to further research on retrotransposon transcriptional activities and functions in Tamarix chinensis,and provide fundamental genetic informations for the utiliazation of retrtransposons in of Tamarix chinensis,such as development retrotransposon molecular markers and research on evolutionary relationship between Tamarix chinensis and other species.