Identification and characterization of the fusion transcript, composed of the apterous homolog and a putative protein phosphatase gene, generated by 1.5-Mb interstitial deletion in the vestigial (Vg) mutant of Bombyx mori T. Fujii a , H. Abe b , S. Katsuma a , T. Shimada a, * a Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657, Japan b Department of Biological Production, Tokyo University of Agriculture and Technology, Saiwai-cho 3-5-8, Fuchu, Tokyo 183-8509, Japan article info Article history: Received 24 October 2010 Received in revised form 13 January 2011 Accepted 24 January 2011 Keywords: Apterous Vestigial Ptp Fusion transcript Interstitial deletion Wing abstract The vestigial (Vg) mutant is a Z-linked mutant that causes vestigial wings in the silkworm, Bombyx mori. We have previously reported a 1.5-Mb interstitial deletion on the Z chromosome bearing the Vg mutation (Z Vg chromosome). In this study, we found that exons 3e8 of a gene named Bmptp-Z encoding a putative tyrosine-specific protein phosphatase are deleted by the 1.5-Mb interstitial deletion. We found that a gene encoding the Bombyx homolog of Drosophila Apterous (BmAp-A) protein is located 4.5 kb downstream of the distal breakpoint of the 1.5-Mb interstitial deletion. Moreover, an in-frame fusion transcript composed of the 5 0 part of Bmptp-Z and the 3 0 part of Bmap-A is generated specific to the Z Vg chromosome. Effects of the in-frame fusion transcript on the vestigial phenotype are discussed. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction One of the most peculiar features of the insect is its ability to fly with wings. Wings have undoubtedly played an important role in the enormous diversification of insects. In holometabolous insects, wings develop rapidly from the wing imaginal disc during larval- pupal development. Hence, insect wings provide an excellent model to study the genetic background of morphogenesis. In addition, knowledge about insect wing development can be applied to pest control. For example, ladybird beetles with RNAi-generated wing defects may improve biological control because they cannot fly away from host plants, and therefore, effectively feed on aphid species (Ohde et al., 2009). Genes that govern wing development are well characterized in dipteran Drosophila melanogaster. The genetic mechanisms for wing development described in Drosophila can be used as a framework to study wing development in other insects. Diverse shapes, colors and markings are observed in lepidop- teran insect wings. However, little is known about the molecular mechanism generating these diversities. In the lepidopteran Bombyx mori, there are more than 400 mutants including wing- related ones (Banno et al., 2005). These mutants are useful to study the molecular basis of lepidopteran wing development. The Vg gene is an X-ray-induced dominant gene that causes the vestigial phenotype of the adult wings of B. mori (Fig. 1). Individuals of þ Vg od/Vg genotype always exhibit the od phenotype (larval epidermis is highly translucent) because the Z chromosome con- taining the Vg gene (Z Vg chromosome) lacks the þ od locus (1e49.6) (Tazima, 1944). Therefore, it was suggested that there is terminal deletion including the od locus in the Z Vg chromosome. Subse- quently, we reported a 1.5-Mb interstitial deletion, and not a terminal deletion on the Z Vg chromosome (Fujii et al., 2008). However, it remains to be clarified why the 1.5-Mb interstitial deletion causes a vestigial phenotype. Here, we report identification and characterization of the in- frame fusion transcript specific to the Z Vg chromosome. We iden- tified exons 3e8 of a gene encoding putative tyrosine-specific protein phosphatase (Bmptp-Z) is deleted by the 1.5-Mb interstitial deletion. Moreover, we found that two copies of B. mori apterous (Bmap-A and Bmap-B) are tandemly located in the vicinity of the proximal breakpoints of the 1.5-Mb interstitial deletion, and an in- frame fusion transcript composed of the Bmptp-Z and Bmap-A is generated due to the 1.5-Mb interstitial deletion. * Corresponding author. Tel.: þ81 3 5841 8124; fax: þ81 3 5841 8011. E-mail address: toru@ss.ab.a.u-tokyo.ac.jp (T. Shimada). Contents lists available at ScienceDirect Insect Biochemistry and Molecular Biology journal homepage: www.elsevier.com/locate/ibmb 0965-1748/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.ibmb.2011.01.007 Insect Biochemistry and Molecular Biology 41 (2011) 306e312