Nested retrotransposons on the W chromosome of the wild silkworm Bombyx mandarina.
The W chromosome of the silkworms Bombyx mori or B. mandarina is recombinationally isolated from the Z chromosome and the autosomes. We previously characterized a female-specific randomly amplified polymorphic DNA (RAPD), designated W-Yamato, derived from the W chromosome of the wild silkworm Bombyx mandarina. To further analyse the W chromosome of B. mandarina, we obtained a lambda phage clone that contains the W-Yamato RAPD sequence and sequenced the 16.7 kb DNA insert. We found that this DNA comprises a nested structure of at least seven elements: six retrotransposons and one transposable element-like sequence. The transposable element-like sequence is inserted into a micropia-like retrotransposon (Karate). The Karate and the non-long terminal repeat (non-LTR) retrotransposon BMC1 are inserted into a 412-like retrotransposon (Judo). Furthermore, this Judo, and two non-LTR retrotransposons (Kurosawa and Kendo) are inserted into a Pao-like retrotransposon (Yamato). These results indicate that the retrotransposons inserted into the W chromosome are not efficiently removed but accumulate gradually as strata without recombination.
Abe
H
H
Department of Biological Production, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Tokyo, Japan. wfem@cc.tuat.ac.jp
Sugasaki
T
T
Terada
T
T
Kanehara
M
M
Ohbayashi
F
F
Shimada
T
T
Kawai
S
S
Mita
K
K
Oshiki
T
T
D000818:Animals; D001483:Base Sequence; D012831:Bombyx / Q000737:chemistry / Q000235:genetics*; D002874:Chromosome Mapping; D004247:DNA / Q000737:chemistry / Q000235:genetics; D005260:Female; D015723:Gene Library; D008297:Male; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D018626:Retroelements / Q000235:genetics*; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012730:Sex Chromosomes / Q000737:chemistry / Q000235:genetics*
D018626:Retroelements; D004247:DNA