Genome-wide characterization of long terminal repeat -retrotransposons in apple reveals the differences in heterogeneity and copy number between Ty1-copia and Ty3-gypsy retrotransposons.
The conserved domains of reverse transcriptase (RT) genes of Ty1-copia and Ty3-gypsy groups of long terminal repeat (LTR) retrotransposons were isolated from the Malus domestica genome using degenerate oligonucleotide primers. Sequence analysis showed that 45% of Ty1-copia and 63% of Ty3-gypsy RT sequences contained premature stop codons and/or indels disrupting the reading frame. High heterogeneity among RT sequences of both Ty1-copia and Ty3-gypsy group retrotransposons was observed, but Ty3-gypsy group retrotransposons in the apple genome are less heterogeneous than Ty1-copia elements. Retrotransposon copy number was estimated by dot blot hybridizations for Ty1-copia (approximately 5,000) and Ty3-gypsy (approximately 26,000). All elements of the two types of LTR retrotransposons comprise approximately 38% of the M. domestica genome, with the Ty3-gypsy group contribution being higher (33.5%) than the Ty1-copia one (4.6%). Transcription was not detected by reverse transcription-polymerase chain reaction for either Ty1-copia or Ty3-gypsy retrotransposons in the leaves of plants in vitro or in leaf explants cultured on medium supplemented with high concentration benzylaminopurine. This research reveals the differences in heterogeneity and copy number between Ty1-copia and Ty3-gypsy retrotransposons in the apple genome. Ty1-copia retrotransposon has higher heterogeneity than Ty3-gypsy retrotransposon, but the latter has a higher copy number, which implies that Ty3-gypsy retrotransposons may play a more important role in the apple genome evolution.
College of Horticulture, Shenyang Agricultural University, Dongling Road 120, Shenyang 110161, China.
Hai-Yue
HY
Sun
Hong-Yan
HY
Dai
Gui-Ling
GL
Zhao
Yue
Y
Ma
Chun-Qing
CQ
Ou
He
H
Li
Lin-Guang
LG
Li
Zhi-Hong
ZH
Zhang
D000595:Amino Acid Sequence; D001483:Base Sequence; D018744:DNA, Plant / Q000235:genetics / Q000302:isolation & purification; D018628:Gene Dosage; D018745:Genome, Plant / Q000235:genetics*; D027845:Malus / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D018626:Retroelements / Q000235:genetics*; D016415:Sequence Alignment; D020079:Terminal Repeat Sequences / Q000235:genetics*; D014158:Transcription, Genetic
D018744:DNA, Plant; D018626:Retroelements