Abstract:

Using degenerate oligoncleotide primers corresponding to conserved domains of the Ty1-copia retrantranspon reverse transcriptase, a fragment of 260 bp was amplified by PCR from Cucumis hystrix and C.sativus. The amplicons were cloned into pGEM-T Easy vector after purification, positive clones selected and identified by colony PCR, then sequenced and analyzed. 21 different sequences of reverse transcriptase from Cucumis hystrix and C. sativus-"Beijingjietou" were obtained, and five families were distinguished after cluster and alignment analyses of their nucleotide sequences. These sequences showed high heterogeneity mainly characterized by deletion mutation. The length of the nucleotide sequences varied from 255bp-272bp, and homology ranged from 27.0% to 98.1%. When translated into amino acids, four sequences presented stop codon mutation, and six sequences presented frameshift mutation. The amino cluster and alignment analyses of these sequences with other reverse transcriptase sequences from other accessions showed that they may have the same origin.

Key words: Cucumis, Ty1-copia-like retrotransposons, reverse transcriptase, heterogeneity