Positional cloning of the sex-linked giant egg (Ge) locus in the silkworm, Bombyx mori

T. Fujii, H. Abe, M. Kawamoto, Y. Banno, T. Shimada

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6 Citations (Scopus)


The giant egg (Ge) locus is a Z-linked mutation that leads to the production of large eggs. Cytological observations suggest that an unusual translocation of a large fragment of the W chromosome bearing a putative egg size-determining gene, Esd, gave rise to giant egg mutants. However, there is currently no molecular evidence confirming either a W-Z translocation or the presence of Esd on the W chromosome. To elucidate the origin of giant egg mutants, we performed positional cloning. We observed that the Bombyx mori. orthologue of the human Phytanoyl-CoA dioxygenase domain containing 1 gene (PHYHD1) is disrupted in giant egg mutants. PHYHD1 is highly conserved in eukaryotes and is predicted to be a Fe(II) and 2-oxoglutarate-dependent oxygenase. Exon skipping in one of the two available Ge mutants is probably caused by the insertion of a non-long terminal repeat transposon into intron 4 in the vicinity of the 5a2 splice site. Segmental duplication in Ge2, an independent allele, was caused by unequal recombination between short interspersed elements inserted into introns 3 and 5. Our results indicate that (1) Bombyx PHYHD1 is responsible for the Ge mutants and that (2) the Ge locus is unrelated to the W-linked putative Esd. To our knowledge, this is the first report describing the phenotypic defects caused by mutations in PHYHD1 orthologues.

Original languageEnglish
Pages (from-to)213-221
Number of pages9
JournalInsect Molecular Biology
Issue number2
Publication statusPublished - Apr 1 2015

All Science Journal Classification (ASJC) codes

  • Molecular Biology
  • Genetics
  • Insect Science


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