Expression of homeotic genes in Bombyx mori estimated from asymmetry of dorsal closure in mutant/normal mosaics

Abstract

AbstractGenetic mosaics of homeotic genes, ENk and ESw, in the silkworm, Bombyx mori, were made using a hereditary mosaic gene, mo. Deformed segmentation, due to asymmetric integumental fusion during dorsal closure, was observed in the mosaics. Left and right integuments that contained an ENk or ESw gene on either side did not fuse symmetrically on the dorsal center line. The asymmetric fusion was observed only in places where the dorsal center lines corresponded to the border line between genotypes. In mosaics of ENk and +E, the sides of segments containing ENk genes frequently fused with anterior parts of the wild‐type side, in the region from the metathorax to the fourth adbominal segment, while on the sixth through eighth abdominal segments they fused with the posterior parts of the opposite sides. In mosaics of ENk and +E, asymmetric fusion was observed in a narrower region, from the metathorax to the second abdominal segment. In this region, the sides containing ESw genes frequently fused with posterior parts of the wild‐type side, in contrast to the fusion observed for ENk mosaics. The cause of asymmetric fusion and expression of the homoeotic genes in degmental differentiation are discussed in terms of a quantitive analysis of the relationship between mosaic patterns and asymmetric patterns of fusion.