Developmental expression of the Bombyx Antennapedia homologue and homeotic changes in the Nc mutant

Abstract

Background: Abundant availability of homeotic mutants in Bombyx mori provides us with clues to study the body plan of the silkworm. Previous studies indicated that the E Ca /E Ca and E N /E N embryos, which reveal drastic morphological changes (Itikawa 1943, 1952) lack the homologue of abd-A and the homologues of abd-A and Ubx, respectively (Ueno et al. 1992). It will be interesting to characterize a mutant named Nc, the locus of which was mapped about 1.4 cm apart from the E loci (Itikawa 1944, 1952).

Antennapedia is involved in the development of thoracic legs and segmentation in the silkworm, Bombyx mori

“…A previous study reported that BmAntp lacked the homeodomain and its downstream region in the B. mori Nc mutant, showing homeotic changes of prothoracic legs into antennae and compression between the prothoracic and mesothoracic segments (Nagata et al, 1996). However, the transformations in Wes homozygotes, such as the appendages under the mouthparts (Figure 1e) and the fused thoracic segments (Figure 1j) are different, to some extent, from that in Nc homozygotes.…”

Hexapoda: Comparative Aspects of Later Embryogenesis and Metamorphosis

“…This role was fi rst identifi ed through loss-of-function mutations in Drosophila , which exhibit partial transformations of legs to antennae (Struhl 1982 ). Disruption of Antp causes similar transformations of legs to antennae in Bombyx (Nagata et al 1996 ), Tribolium (Beeman et al 1993 ), andOncopeltus (Angelini et al 2005 ). In hexapods, Ubx specifi es T3 identity in part by blocking T2 identity.…”

Expression profiling of homeobox genes in silk gland development in the mulberry silkworm Bombyx mori

“…Six Hox genes have been characterized in the silkworm, Bombyx mori: Scr, Dfd, Antp, Ubx, abdA and AbdB Mase et al 1994;Nagata et al 1996;Kokubo et al 1997). The silk glands of Bombyx are the site of silk protein synthesis and are divided into three morphologically and functionally distinct compartments: anterior (ASG), middle (MSG) and posterior (PSG).…”

“…The silk glands span the entire length of the insect body and thus are likely to be exposed to various Hox products during the course of their development. Bm Antp is expressed strongly in the three thoracic segments and also in the middle silk glands (Mase et al 1994;Nagata et al 1996). In Nc mutant embryos (in which the 3 0 region of Antp is deleted), besides the transformation of the first thoracic segment legs to antennae, the silk glands are also reduced (Nagata et al 1996), suggesting a possible role for Antp in silk gland development.…”

“…Bm Antp is expressed strongly in the three thoracic segments and also in the middle silk glands (Mase et al 1994;Nagata et al 1996). In Nc mutant embryos (in which the 3 0 region of Antp is deleted), besides the transformation of the first thoracic segment legs to antennae, the silk glands are also reduced (Nagata et al 1996), suggesting a possible role for Antp in silk gland development. This mutation expands the expression domain of Scr towards the posterior region, leading to the ectopic expression of Fkh and induction of extra pairs of silk glands (Kokubo et al 1997).…”