Mdoryco1-1, a bidirectionally transcriptional Ty1-copia retrotransposon from Malus x domestica

Most retrotransposons from plants are believed to be either transcriptionally inactive or transcriptionally silent in somatic tissues but active during particular stages of development or under certain conditions. We have identified a bidirectionally transcriptional apple Ty1-copia-like retrotransposon called Mdoryco1-1, which was associated with apple spur mutation. Mdoryco1-1 belongs to a low-copy-number family in the sequenced apple genome. These copies were highly similar. The sense and antisense strands of the 5'-LTR (long terminal repeat) and 3'-LTR drove expression of GUS in transiently transformed tobacco leaves, activity which was dependent on the presence of the promoter function in the Mdoryco1-1 LTR. The transcriptional activity of Mdoryco1-1 was increased after ABA (abscisic acid), wounding and 2,4-D (2,4-dichlorophenoxyacetic acid) treatments, but not SA (salicylic acid) treatment, despite the predicted TCA-element (cis-acting element involved in salicylic acid responsiveness) in the Mdoryco1-1 LTR sense strand. The analysis of flanking sequences indicates that the Mdoryco1element is adjacent to genes in apple genome. The results suggested that the expression of Mdoryco1 could affect adjacent gene transcription. (C) 2017 Elsevier B.V. All rights reserved.