Isolation and characterization of sex chromosome rearrangements generating male muscle dystrophy and female abnormal oogenesis in the silkworm, Bombyx mori.
In deletion-mapping of W-specific RAPD (W-RAPD) markers and putative female determinant gene (Fem), we used X-ray irradiation to break the translocation-carrying W chromosome (W( Ze )). We succeeded in obtaining a fragment of the W( Ze ) chromosome designated as Ze (W), having 3 of 12 W-RAPD markers (W-Bonsai, W-Yukemuri-S, W-Yukemuri-L). Inheritance of the Ze (W) fragment by males indicates that it does not include the Fem gene. On the basis of these results, we determined the relative positions of W-Yukemuri-S and W-Yukemuri-L, and we narrowed down the region where Fem gene is located. In addition to the Ze (W) fragment, the Z chromosome was also broken into a large fragment (Z(1)) having the +( sch ) (1-21.5) and a small fragment (Z(2)) having the +( od ) (1-49.6). Moreover, a new chromosomal fragment (Ze (W)Z(2)) was generated by a fusion event between the Ze (W) and the Z(2) fragments. We analyzed the genetic behavior of the Z(1) fragment and the Ze (W)Z(2) fragment during male (Z/Z(1) Ze (W)Z(2)) and female (Z(1) Ze (W)Z(2)/W) meiosis using phenotypic markers. It was observed that the Z(1) fragment and the Z or the W chromosomes separate without fail. On the other hand, non-disjunction between the Ze (W)Z(2) fragment and the Z chromosome and also between the Ze (W)Z(2) fragment and the W chromosome occurred. Furthermore, the females (2A: Z/Ze (W)Z(2)/W) and males (2A: Z/Z(1)) resulting from non-disjunction between the Ze (W)Z(2) fragment and the W chromosome had phenotypic defects: namely, females exhibited abnormal oogenesis and males were flapless due to abnormal indirect flight muscle structure. These results suggest that Z(2) region of the Z chromosome contains dose-sensitive gene(s), which are involved in oogenesis and indirect flight muscle development.
Fujii
T
T
Department of Biological Production, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Saiwai-cho 3-5-8, Fuchu, Tokyo 183-8509, Japan.
Yokoyama
T
T
Ninagi
O
O
Kakehashi
K
K
Obara
Y
Y
Nenoi
M
M
Ishikawa
T
T
Mita
K
K
Shimada
T
T
Abe
H
H
D000818:Animals; D012831:Bombyx / Q000235:genetics*; D002869:Chromosome Aberrations; D002874:Chromosome Mapping; D005260:Female; D017353:Gene Deletion; D005819:Genetic Markers; D008297:Male; D008957:Models, Genetic; D009136:Muscular Dystrophies / Q000235:genetics; D009866:Oogenesis; D012730:Sex Chromosomes; D012737:Sex Factors; D014178:Translocation, Genetic
D005819:Genetic Markers