Regional expression of the transcript encoding sterol carrier protein x‐related thiolase and its regulation by homeotic genes in the midgut of Drosophila embryos

Abstract

We have isolated a gene designated terminal rings in the midgut (trim), which encodes a transcript expressed in the embryonic midgut in a region-specific manner. The 1.4 kb trim transcript is expressed in two discrete regions of the midgut epithelium during late embryogenesis. The anterior domain of trim expression is found between the proventriculus and the first midgut constriction. The posterior domain locates in the region posterior to the third midgut constriction. Furthermore, we show that normal function of two homeotic genes, Antp and abd-A, which express in the visceral mesoderm covering the midgut epithelium, is required for the regional expression of trim. The trim gene is thus reasoned to be activated through inductive interaction between two midgut layers. The 1.4kb mRNA encodes a sterol carrier protein x-related thiolase. As thiolase activity is required for lipid metabolism, the expression of the 1.4 kb trim transcript can represent a state of differentiation and can be used as an appropriate marker for analyzing regional differentiation of the midgut in terms of physiologically distinct domains.